aerOsPaCe sPeCIaL rePOrt - MDXmdx2.plm.automation.siemens.com/sites/default/...02 aerospace report Introduction by Deryl Snyder aerOsPaCe ... associate editors Prashanth Shankara -

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Designing a Drag-Free storage Locker

aeroacoustics for aerospace

uaV Close Formation Flight

aerOsPaCe sPeCIaL rePOrt

Follow us online.For more information: [email protected] www.cd-adapco.com/industries/aerospace

Simulation Software for a New Frontier in Engineering Innovation

star-CCM+: engineering success

Delivering the power of integrated fluid dynamics & heat transfer simulation technology

with the ease of automated meshing of complex geometries

sOLutIONs tHat sPaN tHe aerOsPaCe INDustrY

INtrODuCtION

02 aerospace report

Introduction by Deryl Snyder

aerOsPaCe

04 New and upcoming Capabilities

For the Aerospace Industry

FeatureD artICLes

08 Learjet 60

Designing a drag-free storage locker

12 uaVs

Close Formation Flight

16 High Lift trapezoidal Wing

Numerical Simulation in STAR-CCM+

20 aeroacoustics

Simulations for the Aerospace Industry

24 From Design Challenge to Flying uaVs

In Fifteen Weeks

28 Virtual Design takes off

Revolutionary Flying Technology

32 star-CCM+ for aerospace applications

reseLLers

australia CD-adapco Australia [email protected] ADCOM Consulting Services (Shmulik Keidar Ltd.) [email protected] Zealand Matrix Applied Computing Ltd. [email protected]

russia SAROV Engineering Center [email protected] africa Aerotherm Computational Dynamics [email protected] A-Ztech Ltd. [email protected]

China

CDAJ-China [email protected]

CDAJ Japan [email protected]

aMerICas

united states New York • Headquarters 60 Broadhollow Road Melville, NY 11747, USA Tel.: (+1) 631 549 2300 Austin TX Cincinnati OH Detroit MI Houston TX Lebanon NH Los Angeles CA Seattle WA State College PA Tulsa OK south america São Paulo, Brazil

eurOPe

united Kingdom London• Headquarters 200 Shepherds Bush Road London, W6 7NL, UK Tel.: (+44) 20 7471 6200 Aberdeen France: Paris, Lyon Germany: Nuremberg Italy: Turin, Rome Norway: Oslo

asIa-PaCIFIC

India: Bangalore Japan: Yokohama, Osaka Korea: Seoul singapore: Singapore

all inquiries, please contact: [email protected]

Global Offices CD-adapco

eDItOrIaL

Dynamics welcomes editorial from all users of CD-adapco software or services. To submit an article, email: [email protected] Telephone: +44 (0)20 7471 6200

editor Stephen Ferguson - [email protected] assistant editor Deborah Eppel - [email protected] associate editors Prashanth Shankara - [email protected] Lauren Gautier - [email protected] Design & art Direction Brandon Botha - [email protected] e-dynamics Mathew Parry - [email protected] advertising sales Geri Jackman - [email protected] us events Tara Firenze - [email protected] european events Sandra Maureder - [email protected]

subsCrIPtIONs & DIGItaL eDItIONs Dynamics is published approximately twice a year, and distributed internationally. All recent editions of Dynamics, Special Reports & Digital Reports are now available online: www.cd-adapco.com/press_room/dynamics

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Contents

reCYCLeD PaPer. VeGetabLe INKs.

04 08

12 16

20 24

28

Follow us online.

02 AEROREPORT

..::INTRODUCTION Deryl Snyder

i EMAIL [email protected]

At CD-adapco, we understand this new reality, and know that in order to be competitive, numerical simulations are rapidly becoming more than just an advantage – they are becoming a necessity. No longer just for analysis at the later

stages of the development process, CFD can and should be applied as a design tool from the beginning. This, of course, requires ease of use, automation and seamless integration with other CAD and CAE tools.

CD-adapco’s user base in the industry is large and rapidly growing, ranging from small start-ups to large corporations. The applications are as varied as the companies: from a single integrated environment, engineers can analyze combustion, multiphase flow, heat transfer, dynamic fluid-body interaction, aeroacoustics, ice management, solid stress, and now batteries and electric machines. Despite this diversity, they all have one thing in common: best-in-class simulation software enabling them to innovate and excel.

This Aerospace Special Report provides a small set of examples and customer case studies demonstrating the benefits that can be achieved by partnering with CD-adapco. I recommend taking some time to read through it and learn what others in the industry are doing with CAE. It may provide insight into how you might succeed in solving the challenges you are facing.

CD-adapco has been providing CAE tools, services, and expertise for over 30 years. We are committed to continuing to improve our current offering and develop new capabilities for this exciting industry.

I welcome you to contact us if you have questions about how our products and services can help with your project or application, or to discuss how to obtain the highest return on your CAE investment.

Deryl Snyder, CD-adapcoDirector, Aerospace & DefenseCD-adapco

aerospace reportIntroduction by Deryl snyder

The applications are as varied as the companies: from a single integrated environment, engineers can analyze combustion, multiphase flow, heat transfer, dynamic fluid-body interaction, aeroacoustics, ice management, solid stress, and now batteries and electric machines.

The aerospace industry is in the process of reinventing i tself in response to global economic, pol i t ical , social , and environmental pressures. I t is no secret that in order to remain competi t ive, companies must increase product performance and reduce the amount of t ime i t takes to get that product to market, while at the same t ime reducing costs. Al though chal lenging, this is an excit ing t ime to be in the industry!

star-CCM+: engineering successDelivering the power of integrated fluid dynamics & heat transfer simulation technology with the ease of automated meshing of complex geometries

Image modeled in STAR-CCM+. Courtesy of Propulsive Wing www.propulsivewing.com

“CD-adapco provides first class support as well as powerful software that is easy to use for our various applications.”

ANdY SLATer, direCTOr - FLigHT SCieNCeS, guLFSTreAm AerOSpACe

sOLutIONs tHat sPaN tHe aerOsPaCe & DeFeNse INDustrY

For more information: [email protected] www.cd-adapco.com/industries/aerospace

www.cd-adapco.com/industries/aerospaceFOR MORE AEROSPACE ARTICLES PLEASE VISIT:

..::Feature artICLe Capabilities

STAR-CCM+ is developed to be accurate, eff icient , easy to use, and, thanks to i ts rapid release cycle of three major releases each year, grow with the needs of our users in mind. We are always improving the technology and capabil i t ies to better solve the problems facing the aerospace industry. This art icle highl ights a few recent and upcoming capabil i t ies.

New and upcoming Capabilities for the aerospace IndustryDeryl snyder, CD-adapco

Overset Meshing Advantages of Overset Meshing have been recognized for many years. In the case of steady flow around bodies at various relative positions, one needs to generate individual grids only once, and then compute the flow for many combinations or relative positions and orientations by simply moving grids, with no need to re-mesh or change boundary conditions.

Applications include control surface deflection studies, parametric studies, or even simple angle-of-attack sweep studies. Flow around bodies moving relative to each other is often easier to handle with overset meshes than with sliding interfaces or deforming grids. The flowfield and 6-Degree-of-Freedom (6DoF)

motion of bodies can be simulated by moving the grid attached to each moving body (with little or no deformation) while the background grid remains stationary. Applications include, to cite but a few, store separation, silo or tube launches, stage separation, etc.

In the past, several drawbacks of overset meshing have limited its widespread use, such as requiring block-structured meshes, tedious pre-processing, and reduced accuracy and stability due to weakly coupled solution approaches. CD-adapco has developed an overset mesh approach that resolves these drawbacks and will move the technology into mainstream CFD simulations.

04 AEROREPORT


Each mesh can be of any type, whether you prefer the general polyhedra mesher, the trimmer mesher, or to import existing grids. In fact, mixing mesh types is not a problem. This means each mesh can be arbitrarily complex, which reduces the number of individual overset meshes needed. A novel solution approach has been developed, where all grids are implicitly coupled within the linearized coefficient matrix of every equation solved.

There are no “internal boundaries” used at the mesh interfaces, and the solution is computed simultaneously on all grids at each iteration. This ensures that the iterative solution method can be converged down to the round-off level of residuals, and that the convergence rate is similar to what would be obtained for the same problem on a single grid. In addition, for the case of dynamic fluid-body motion,

the equations of motion are fully implicit and fully coupled with the flow solution, meaning larger time steps and better stability than with explicit schemes. The first set of overset meshing functionalities is available in STAR-CCM+ v7, with many enhancements and improvements planned for the future.

Advancing Layer Mesher It is apparent that unstructured meshes have come of age, and are now generally accepted as providing excellent handling of complex geometry and sufficient accuracy for both internal and external flows. This is possible due to the so-called hybrid mesh approach, where prismatic cells are used in regions where the flow is dominated by viscous effects (namely within the boundary layer), g

ABOVE AND BELOWSimple pitching airfoil images show smooth contours across the overset mesh interface and integration of streamlines across the different mesh regions. Complex geometries such as those seen in store separation can be easily accommodated without the user needing to worry about the details of cell activation/deactivation or interpolation.

05 AEROREPORT


and general unstructured cells are used in the remainder of the computational domain. STAR-CCM+ provides a robust state-of-the-art prismatic mesher and general polyhedral or Cartesian unstructured meshers. Still, there are applications where smoothly growing, primarily structured body-aligned meshes are advantageous; for instance, computations involving bow shocks, where the mesh needs to be aligned with the flow direction and gradients of the transported values in order to reduce truncation errors and numerical diffusion. The Advancing Layer Mesher, first available in STAR-CCM+ v7 uses a pseudo-structured mesh approach to generate layered, primarily structured grids from wall boundaries. Although this may sound similar to the Prism Layer mesher, there are key differences that make the models suitable for different applications. In the case of the Advancing Layer Mesher, the prismatic cell layers are generated from the polygonal surface mesh into the volume, rather than using an inflation approach like the Prism Layer mesher. This allows the Advancing Layer Mesher to generate a thicker layer and maintain a more uniform wall distance, meaning that the layered region can grow beyond the boundary layer to provide smooth, wall-aligned meshes in the mid-field. Users will note a resemblance to structured hyperbolic meshes, but with significantly improved robustness because the algorithm can collapse and split faces and edges, thereby improving mesh quality and reducing cell skewness.

Battery Design It is nearly impossible to miss the significant development efforts the automotive industry has made in electric vehicles in recent years, specifically in power storage and delivery via batteries. Although it hasn’t received the same media attention, batteries play a crucial and growing role in the aerospace industry.

For instance, spacecraft have used batteries to store energy for decades. Lithium ion batteries are relatively new to this application, but the potential impact of this technology on the industry is significant. The traits that make these batteries attractive to the automotive industry are especially critical to spacecraft, namely lightweight, small volume, high specific energy and long cycle life.

Closer to home, micro- and tactical-sized Unmanned Aerial Vehicles (UAVs) already utilize a fully-electric power solution – including propulsion. For mainstream aviation, batteries are currently strictly used for startup and backup power; for instance, to run navigation and critical systems when the Auxiliary Power Unit (APU) is off, or in case of an emergency. However, the recent CAFe Foundation green Flight Challenge was dominated by two fully electric-powered aircraft that delivered as much as 400+ passenger miles-per-gallon equivalent – more than twice that of the fossil-fuel-powered aircraft in the competition. Clearly, batteries will play an

important role in the future of the aerospace industry in much the same way as it will for the automotive industry.

To address this key technology, CD-adapco partnered with Battery Design, LLC several years ago to develop a best-in-class simulation environment for battery analysis and design. The resulting STAR-CCM+ Battery Simulation Module (BSM) calculates the 3D thermal, fluid and electrochemical phenomena of lithium-ion battery cells within a full range of length scale models. These simulations start from the electrode pairs within the battery cell, to the entire pack, including thermally and electrically-conducting parts such as metallic connectors which have a significant effect at high discharge/charge rates. This is all done within the familiar user-friendly STAR-CCM+ user environment.

Specifically, all of the fluid flow and heat transfer capabilities, including multiple fluid/solid domains, conjugate heat transfer, multiphase flow, radiation, etc. available in STAR-CCM+ are coupled to a full range of cell models. By simultaneously solving the electrical and thermal problems, the close-coupled nature of this system can be analyzed, providing engineers with previously unseen data. Moreover, the user has the ability to control the details of the simulation, both in terms of geometric fidelity and appropriate mathematical models, thereby ensuring that analyses are tailored to the user’s needs and resources. These models include a state-of-the-art detailed electrochemistry model which can deal with multiple active materials regularly seen in contemporary Li-ion cell design.

One of the key challenges in this type of analysis is establishing a clear engineering process – from battery pack design and experimental cell data to a reasonable simulation result. Much effort has been devoted to developing this process, and the result is a cutting-edge engineering tool, able to deliver fast, and consistently realistic results. <

i mOre STOrieS LiKe THiS CAN Be FOuNd Here: www.cd-adapco.com/industries/aerospace

06 AEROREPORT

BELOWSTAR-CCM+ Battery Simulation Module enables state-of-the-art battery analysis: from single cell, to stack, to system installation.


The Advancing Layer Mesher, first available in STAR-CCM+ v7 uses a pseudo-structured mesh approach to generate layered, primarily structured grids from wall boundaries.

LEFTThe Advancing Layer Mesher builds smooth, body-aligned prismatic cells from wall boundaries to a greater thickness – perfect for external aerodynamics analyses.

ABOVEAdvancing Layer Meshing

07 AEROREPORT

..::Feature artICLe Design

After evaluating a number of options, Raisbeck Engineering decided to invest in STAR-CCM+ due to its ability to address all of Raisbeck’s requirements.

raisbeck engineering designs, develops and produces unique solutions through advanced technology and innovative engineering that enhance the performance and operational efficiency of aircraft. www.raisbeck.com

❐ FACTS

Manufacturer Bombardier AerospaceClass Twin-engine Corporate Jet Crew 2Passengers Max. 8Propulsion 2 Turbofan EnginesMax. thrust 4,600 pounds (20.46 kN) engine Model Pratt & Whitney PW305Aengine Power (each) 23,2 kN 5225 lbfspeed 887 km/h 551 mphservice Ceiling 15.545 m 51.000 ftrange 4.441 km 2.760 mi.

empty Weight 6.641 kg 14.641 lbsmax. takeoff Weight 10.659 kg 23.500 lbs

Wing span 13,40 m 44,0 ftWing area 24,6 m² 265 ft²Length 17,80 m 58,4 ftHeight 4,36 m 14,3 ft First Flight January 18, 1990Production status Still in production

INterNaLCabin length 17.67 ft 5.39 mCabin max. width 5.95 ft 1.81 mCabin width (floorline) 3.9 ft 1.19 mCabin height 5.71 ft 1.74 mFloor area 68.9 ft2 6.40 m2

total volume 453 ft3 12.80 m3

LearJet 60 - sPeCIFICatIONs

08 AEROREPORT


a market study conducted by raisbeck engineering Inc. revealed that increased baggage capacity was the number one request from Learjet 60 operators. as a result, raisbeck engineering decided to pursue the opportunity of creating an aft Fuselage Locker (aFL)

similar to the raisbeck’s aFL for the Learjet 30-series aircraft.Six months before launching the Learjet 60 AFL program, Raisbeck Engineering

made a decision to stop outsourcing CFD and bring it in-house in an effort to expand hands-on knowledge, reduce development time, and increase control of priorities. After evaluating a number of options, Raisbeck Engineering decided to invest in STAr-CCm+ due to its ability to address all of raisbeck’s requirements. After becoming familiar with the package, the next step for Raisbeck Engineering was to obtain a digital model of the Learjet 60 geometry.

Geometry To ensure the aircraft was accurately represented, Raisbeck Engineering invested in digitizing a full-scale Learjet 60. To accomplish the task, white light interferometry scanning was used. The technique involves projecting fringe patterns onto the aircraft from varying distances, capturing resulting interference patterns g

The Aft Fuselage Locker for the Learjet 60 marks a milestone for Raisbeck Engineering. The program is the f irst to use an in-house CFD capabil i ty at Raisbeck, and also the f irst Raisbeck product for the Learjet 60. For this program, a zero-drag penalty goal was set , achieved in simulat ions and val idated in f l ight test .

Designing a drag-free storage locker for the Learjet 60Davud Kasparov, raisbeck engineering Inc.

INterNaLCabin length 17.67 ft 5.39 mCabin max. width 5.95 ft 1.81 mCabin width (floorline) 3.9 ft 1.19 mCabin height 5.71 ft 1.74 mFloor area 68.9 ft2 6.40 m2

total volume 453 ft3 12.80 m3

aVIONICsAll-digital Collins Pro Line 4 four-tube EFISdual AHrSWXR840 weather radarDual nav/comm systemsDual UNS-1C FMS

NOIse LeVeL (ePNDb)Takeoff 78.9 dbApproach 87.7 dbSideline 83.2 db

i dOWNLOAd THe LATeST AerOSpACe repOrT: www.cd-adapco.com/downloads/special_reports

ABOVELearjet 60 being prepared for white-light scanning with reference markers

09 AEROREPORT

and intensities with multiple cameras, and finally resolving the geometry by reducing data in the frequency domain. The resulting point cloud, representing half of the aircraft to an accuracy of under 0.01 inches, consisted of over 35 million points. Surfaces were then lofted, conforming to the scan data while simplifying the geometry by excluding minor details such as rivets, gaps, small antennas, etc. With the aircraft geometry in hand, brainstorming could begin.

Goals & Constraints Before the conceptual design of the aft fuselage locker (AFL) shape began, physical constraints were set to, among other things, ensure the AFL did not strike the ground during take-off rotation. Additionally, the target cargo capacity was set at 300 lbs and 25 cubic feet. Most shapes considered for the AFL could be split into 3 categories with varying degree of cargo capacity: those that ended with a fin, those without a fin, and hybrids (see image for a comparison of the shapes). With each concept, attributes such as cargo volume, external wetted area, and ease of manufacturing were considered and weighed against the results of CFD simulations.

Performance To evaluate the aerodynamic performance of each concept, a range of cruise conditions was picked from two sources, the aircraft flight manual and operator feedback. At each flight condition, the aircraft with a concept shape attached was trimmed in angle of attack for the target lift and with the incidence of the horizontal tail for a zero pitching moment about its center of gravity. The parameter summarizing overall aerodynamic performance, used to compare all configurations with respect to baseline, was the lift to drag ratio, or L/D. Pressure distributions were monitored to ensure high suction peaks were not introduced, as shown in accompanying image..

simulation In terms of simulation, all analysis was conducted in STAR-CCM+. Simulations were run in steady state with Menter’s SST K-ω turbulence model, which previously had been shown to produce good agreement in internal validation studies. In order to meet strict deadlines, a mesh consisting of approximately 6.5 million polyhedral cells was used to enable the calculation of a trimmed flight condition in less than 48 hours on a 24-node cluster.

results: CFD Analysis revealed that at all cruise conditions, all concepts showed an absolute change in L/D of less than 1% when compared to the baseline configuration. This was within the accuracy found in earlier validations. Out of curiosity, an aerodynamically dirty shape was simulated that showed a change in L/D of -4% (increase in drag). With the knowledge gained through CFD simulations, the design candidate with attributes of a large cargo capacity and a simple manufacturing process was chosen to be flight tested.

results: Flight test The main goal of flight test was to validate the zero drag of the AFL. As a result, only the external shape of the locker was required. To build the flight test article, a single block of high density foam was machined as a master. Eight plies of pre-impregnated composite were then laid up, with honeycomb cores and bulkheads added in crucial areas, and cured to yield a shape measuring 24 feet in length. Flight test results indicated that STAR-CCM+ predictions agreed within acceptable accuracies to the flight test measurements, and that the goal of zero-drag penalty was achieved. Conclusions Raisbeck Engineering has digitized a Learjet 60 aircraft, designed a drag-free locker with the help of STAR-CCM+ and confirmed results in flight test. The Aft Fuselage Locker for the Learjet 60 is now in the detailed design phase where the internal mechanics, manufacturing, and other details are being addressed. When complete, this post-production and aftermarket modification will not only enable aircraft operators to carry more baggage but will also enhance the aircraft’s performance. <


ABOVELearjet 60 with Raisbeck Aft Fuselage Locker on first flight

BELOWLift to drag ratio comparison between CFD and flight test results

10 AEROREPORT


BELOWCAD model of the Raisbeck AFL in detailed design phase

ABOVEGeneralized AFL candidate shapes, viewed upside down: finned (left), finless (center), and hybrid (right)

BELOWPressure distribution comparison, side view: finless

locker (bottom) vs. baseline (top) at Mach 0.72. Some aircraft components were visually omitted for clarity.

With the knowledge gained through CFD simulations, the design candidate with attributes of a large cargo capacity and a simple manufacturing process was chosen to be flight tested.

11 AEROREPORT

CFD analysis of aerodynamic Interactions between uaVs in Close Formation Flight

BELOWVertical component of the velocity field around UAV1 and UAV2 shown in a xy-plane located right above the wing upper surface

..::Feature artICLe UAV

Dr. Deborah eppel, CD-adapco

ABOVESpanwise component of the velocity field around UAV1 and UAV2 shown in a xy-plane located right above the wing upper surface

12 AEROREPORT

The last decade has seen an increased interest in the development of Unmanned Aerial Vehicles (UAVs) and their applications, no longer restricted to the military field of operations. UAVs – either remotely piloted or fully autonomous – provide a safer, cheaper alternative to larger, piloted aircraft, as well as a valuable “bird’s eye” observation platform, mid-way between ground-based sensors and high-flying satellites.

these considerations have opened the way UAV applications in many other fields, such as homeland security (police surveillance, border patrol, etc.), public services (fire fighting, search and rescue, power-line and pipeline inspections, chemical and pollution sensing,

climate monitoring, etc.), and the commercial sector (geographic surveys, aerial communications networks, crop spraying, etc.), and made them the choice of predilection to perform the ``3d’’ (dirty, dull and dangerous) missions. However, as some missions – such as air-to-air refuelling, weapons re-loading, aerial launch & recovery or aerial surveillance – require multiple vehicle close formation deployments, a detailed understanding of the wake vortex effects caused by one vehicle upon another is needed.

This article aims at demonstrating how the CFD software STAR-CCM+ can be used to investigate the nature of dynamic air vehicle interactive coupling and its consequences during close formation flights. A formation of two identical tailless pusher UAVs is considered for these purposes. Both vehicles are flying at the same level in a station keeping scenario, and the follower is located 0.9 wingspan behind and 0.9 wingspan starboard of the leader. In the remainder of this article, the leading and following UAVs are referred to as UAV1 and UAV2 respectively.

The entire simulation process, from pre-processing to post-processing, is performed using CD-adapco’s star software STAR-CCM+. STAR-CCM+’s high level of automation enables the user to focus on engineering data analysis rather than on time-consuming repetitive tasks, as demonstrated through the following steps: 1. The airframe geometry of one Pusher UAV – UAV1 – is imported and automatically cleaned up and prepared for meshing: STAR-CCM+’s surface wrapping feature enables any imported geometry, regardless of its complexity and initial quality, to be covered by a clean ̀ `second skin’’ surface mesh. This optional operation can be performed within a few minutes using STAR-CCM+, thereby sparing the CAD and CFD engineer of long and dull hours (if not days) of surface repairing where each individual cell needs to be addressed independently.

2. UAV2 is generated by simply copying and pasting UAV1 to the desired location. This operation can be repeated each time a UAV needs to be added to the formation. g


ABOVEVorticity magnitude behind UAV1

ABOVETangential velocity field behind UAV2

13 AEROREPORT


star-CCM+ PrODuCt Features

Single Integrated Process

STAR-CCM+’s unique simulation process delivers unrivaled

ease-of-use and automation to accurate, engineering CFD.

CAD Embedding

Powerful CFD from within your chosen CAD package:

SolidWorks, Pro/E, CATIA V5 or Unigraphics NX.

Surface Wrapping

Spending hours or days cleaning CAD or preparing a

surface mesh? The Surface Wrapper will cut this time to

minutes.

Automatic Meshing Technology

Advanced automatic polyhedral or hexahedral meshing

gives the ultimate combination of speed, control and

accuracy.

Additional Physics Modeling

The fastest developing solution in CFD, STAR-CCM+ is

equipped with a comprehensive selection of physics

models. Accurate solutions in an easy-to-use environment.

Turbulence

With its extensive selection of turbulence models,

STAR-CCM+ is guaranteed to meet your requirements.

Post-processing

From contours plots, to XY-graphs and streamlines to

animations. Extract Engineering insight with STAR-CCM+.

Software and Hardware Technology

Client-server architecture, object-oriented programming

and unrivaled parallel performance, STAR-CCM+ uniquely

utilises the latest technology.

3. A large boundary volume enclosing UAV1 and UAV2 is then chosen and meshed, using either tetrahedral, polyhedral, or trimmed (hexahedral) cells. The use of polyhedral meshing, which is another of STAR-CCM+’s innovative features, can provide the same accuracy as a typical tetrahedral mesh with at least 5 times fewer cells. Once again, STAR-CCM+ enhances productivity and efficiency without compromising the accuracy of the solution.

4. Several levels of mesh refinement are set up through the use of volumetric controls in order to fully capture UAV1’s wake and its effects on UAV2.

5. The properties of the physics continuum are then defined, including the model to be used, its reference values and initial conditions.

STAR-CCM+ is now ready to perform the computation, at the end of which the solution can easily be analysed using STAR-CCM+’ colourful and powerful post-processing tools.

The post-processing results –shown in accompanying figures – clearly illustrate the evolution of the wake vortices behind the wings of the UAVs. They confirm the well-known fact that wake vortices represent severe atmospheric disturbances which can be – depending on the relative positions of the air vehicles in the formation – either beneficial or detrimental, not to say dangerous. Dangerous because of the strong and sometimes unexpected rolling moment that can be induced on a wake-encountering vehicle by such a concentrated core of vorticity. Beneficial because if the follower positions itself in the up-current generated by the leader, the induced drag of the trailing aircraft is dramatically reduced, leading to significant fuel savings and/or an increased range with a given payload. This translates into real economic and environmental benefits, which are certainly not to be overlooked in a time when the emphasis is set on developing newer, greener and cheaper technologies.

This trick has not been invented by CFD engineers: geese and ducks have been using it in their migration V-formation shapes since the beginning of time.

However, STAr-CCm+’ colourful post-processing tools enable the CFd engineer to demonstrate it in a more artistic way than ever before. Not just Art for Art’s sake though... STAR-CCM+, with its fast, powerful and user-friendly all-in-one integrated environment, proves to be the ideal platform to assess the benefits, as well as the risks and issues, associated with wake vortex evolution and encounter, thereby providing the enabling science on which the development of new procedures and protocols for UAV close formation deployments may be securely based. <

i ViSiT Our NeW AerOSpACe HuB: www.cd-adapco.com/applications/aerospace

RIGHTTangential velocity field behind UAV2

RIGHTGeese flying ‘V Formation’

14 AEROREPORT


15 AEROREPORT

..::Feature artICLe Validation

Prashanth shankara, CD-adapco

Numerical simulation of High Lift trapezoidal Wing with transition Modeling in star-CCM+

www.cd-adapco.com/industries/aerospaceRead about how our software is used in the Aerospace industry:

reFereNCes:

[1] K. Suluksna, P. Dechaumphai, and E. Juntasaro (2009). “Correlations for Modeling Transitional

Boundary Layers under Influences of Freestream Turbulence and Pressure Gradient”. International Jounal of

Heat and Fluid Flow, Vol. 30, pp. 66-75.

[2] Malan P., Suluksna K., Juntasaro E., (2009), “Calibrating the γ-Reθ Transition Model for

Commercial CFD”, AIAA-2009-1142-298, 47th AIAA Aerospace Science Meeting, Jan 2009

16 AEROREPORT

Computations and validation were based on the guidelines and experimental data provided for the 1st AIAA High Lift Prediction Workshop (HiLiftPW-1) to assess the numerical prediction capability of STAR-CCM+ for high lift configurations. STAr-CCm+’s unique automated polyhedral meshing capability was utilized for these simulations, along with predictive transition modeling. Simulations were run for ‘Configuration 1’ from the workshop with the flap at a 25 degree deflection. Force coefficients of lift, drag and pitching moment were computed from STAR-CCM+ for varying angles of attack from 6° to 37° and compared to experimental results.

Geometry and test DescriptionThe geometry chosen for the validation of high lift prediction is the NASA trapezoidal wing geometry available in public domain. The trap wing (shown in image) is a three element, high lift landing configuration with a slat deflection angle of 30 degrees and flap deflection angle of 25 degrees. Two more configurations, one with the flap at 20 degree deflection and another including flap brackets under the wing, will be simulated at a later stage. The three element wing consists of full span slat and flap, with a mean aerodynamic chord of 39.634 inches, aspect ratio of 4.561 and a semi-span of 85 inches.

The experiments on the trap wing were conducted in the 14x22 foot Subsonic Wind Tunnel at NASA Langley Research Center. The tests involved a semi-span model at a Reynolds number of 4.3 million, Mach No. of 0.2 and under free transition (i.e. no tripping mechanisms for transition). Pressure measurements were taken at over 700 surface locations but for the purpose of validating the numerical results, pressure coefficients at span-wise pressure tap rows were given. detailed summary of the experiments can be found on the HiLiftpW-1 website (www.hiliftpw.larc.nasa.gov). g

This art icle detai ls results from the numerical simulat ions on the NASA Trapezoidal Wing geometry, focusing on the high l i f t predict ion using CD-adapco solver, STAR-CCM+.

Numerical simulation of High Lift trapezoidal Wing with transition Modeling in star-CCM+

ABOVE3D view of the Trap Wing Geometry with flap deployed

Did You Know?

Automatic Surface Repair is

available in STAR-CCM+.

This feature cuts geometry

preparation time down from

days to minutes.

trap Wing GeometryCruise Wing Configuration

CD reference Parameters*Reference Area: 22.028 ft2

Mean aerodynamic chord: 39.634 inSemi-span: 85.054 inAspect ratio: 4.561LE Sweep: 33.89 deg1/4 c sweep: 29.97 degTE Sweep: 16.24 degTip cruise chord: 21.116 inRoot cruise chord: 53.473 inMoment Reference: x=34.342 in y=-0.95 in z= 0 in


16 17 AEROREPORT


BELOWView of surface mesh on the suction side

18 AEROREPORT

Computational MeshThe computational mesh was generated using the automatic meshing capability

of STAR-CCM+ and the computational domain was discretized using polyhedral volume cells. Three grids of varying sizes referred to as coarse, medium and fine (accompanying image), were generated for grid convergence study. Grid convergence was studied at the angles of attack, 13 and 28 degrees, as per the workshop guidelines. Grid sizes and characteristics are shown in the following table.

To accurately capture the flow in the boundary layer, a prism layer mesh consisting of hexahedral cells was created around the wing, with 25 layers of cells on the top, bottom and leading edge of the wing. The number of prism layers was reduced in areas like trailing edge and coves, where the boundary layer is not prominent.

The coarse mesh solution was used to identify areas of flow where mesh refinement is required and the in-built 3d CAd modeler of STAr-CCm+ was used to generate 3 dimensional objects of arbitrary shapes in these areas for refinement purposes. The Volumetric Refinement feature of STAR-CCM+ allows us to use a specified mesh size within the control volumes created in 3D CAD Modeler.

ABOVESketch of stowed configuration showing pressure tap locations

ABOVE3D view of the geometry showing span-wise cuts for pressure predictions

Grid Size Cells across TE Size of near wall cell (m) Coarse 11M 6 5e-6Medium 33M 10 3.1e-6Fine 46M 15 1e-6

trap Wing Modelsketch of stowed configuration full-span flap pressure tap layout

BELOW Computational mesh at 50% span showing mesh refinement zones

BELOW LEFT & RIGHTMid-span section view of mesh near wing leading edge - Coarse (left) & Fine (right

BELOW TOP TO BOTTOM Time sequence of images with flow streamlines on the trap wing showing separation

AOA=13

AOA=28

AOA=37

solution using star-CCM+ and transition ModelingThe simulations were carried out using CD-adapco’s flagship software, STAR-CCM+. STAR-CCM+ is an unstructured, cell centered, finite volume, Navier Stokes solver that has been well validated for a variety of aerospace applications. The boundaries of the computational domain were modeled as a freestream boundary with a Mach No. of 0.2 and Reynolds Number of 4.3 Million based on mean aerodynamic chord (MAC).

All simulations were computed using the steady state, coupled flow solver with implicit integration and second order discretization. Flow turbulence was modeled using the SST (Menter) k-ω turbulence model.

The reason for the choice of this turbulence model was to facilitate the use of the correlation based Gamme Re-theta transition model in STAR-CCM+. The transition model works only in conjunction with the SST (Menter) k-ω turbulence model. The Langrty/Menter transition model in literature is incomplete due to the omission of two critical proprietary correlations. The Gamma Re-theta model in STAR-CCM+ uses internally specified correlations based on the data from Suluksna et. al (1) and has been validated by Malan et. al. (2) Transition in the flow can be identified through a combination of Intermittency and Turbulence Intensity plotted chord-wise. An example of transition identification from these two parameters is shown in the images below.

For the grid convergence study, all solutions were started from scratch and the results from the three different sized grids were deemed reasonable enough, with the coarse grid showing the maximum deviation from experimental results by around 4%. The final computations were all run on the medium grid at seven different angles of attack: 6, 13, 21, 28, 32, 34 & 37. Force and moment coefficients were monitored to determine convergence. Computations were started without the transition model to achieve stability and then the transition model was invoked to get to the final solution.

All simulations were initialized using the grid Sequencing technique for faster convergence due to the relatively large CFL numbers that can be used. The Grid Sequencing initialization follows up the normal initialization by computing an approximate inviscid solution by generating a series of coarse meshes from the initial grid and computing solutions from the coarsest to the finest mesh.

results The lift, drag and pitching moment coefficients from STAR-CCM+ were compared to the values from the experiment at all seven angles of attack (shown in image). The numerical predictions from STAR-CCM+ agree well with experimental data. At 37 degrees, massive separation occurs and the wing experiences abrupt stall. Although difficult to predict numerically, STAR-CCM+ is rather successful at estimating the loads near this condition.

To gain more insight into the numerical prediction, surface pressure coefficients at various sections along the span are computed and compared against experimental data. A sample of the comparison at section cuts near root, mid-span and tip is shown below at 13 and 28 degrees. As expected, numerical predictions are excellent along root and mid-span but deteriorate towards the wing-tip. Wing-tip grid resolution and highly varying pressure gradients due to vortex roll-up from the wing-tips is a possible cause for under-prediction. Surface pressure prediction at slat shows excellent agreement with test data at all angles of attack. Flow visualization at a surface and volume level was then used to identify the separation and vortex formation behavior at different angles of attack. Surface streamlines show trailing edge separation along the flap span at lower angles of attack and this characteristic decreases as the angle of attack increases. At higher angles of attack, flow streamlines show very small trailing edge separation on the flap. Flow streamlines clearly show the increase in separation as the angle of attack increases.

Overall, the first round of simulations clearly show that STAR-CCM+ accurately predicts the flow physics of the high-lift configuration. Future work includes further investigation of the wing-tip region, hysteresis effects, effect of support brackets and much more. The first step towards successfully validating STAR-CCM+ for high lift configurations has been completed. The latest/upcoming features of STAR-CCM+ such as body-fitted meshing and chimera grid will also greatly enhance the process/predictability of high-lift aerodynamics. <


i FOR MORE PRODUCTS: www.cd-adapco.com/products

19 AEROREPORT

BELOW Intermittency at center plane section showing transition from laminar to turbulent flow, shown by black circle

BELOW Intermittency at center plane section showing transition from laminar to turbulent flow, shown by black circle

Lift Prediction - Config 1

Drag Prediction - Config 1

Pitching Moment Prediction - Config 1

..::Feature artICLe Aeroacoustics

One of the greatest chal lenges facing the aerospace industry is improving the aeroacoustic noise generat ion of their products to meet today’s more and more str ingent noise pol lut ion standards. As f low-induced noise makes a signif icant contr ibut ion to the overal l output decibels, i t seems essential to understand how to opt imize the aircraft design in order to minimize the f low-induced noise without impairing the general performance of the air-vehicle.

aeroacoustics simulations for the aerospace IndustryFred Mendonça & Deborah eppel, CD-adapco

Case Studies Sources of flow-induced noise are varied. Typically, for commercial aircraft, they are mainly associated with high-lift devices, landing gear, jet nozzles, and cabin and cockpit climate control devices. For military air-vehicles, structural and aerodynamic instabilities of weapons and weapons bays are additional issues that need to be addressed.

This article describes two case studies, namely the airframe noise simulation of a complex nose landing gear, and the aeroacoustics analysis of an avionic cooling rack in an Airbus cockpit.

20 AEROREPORT


ABOVEUniform cubic cells were used in the vicinity of the nose-gear components: 0.75 mm (left), 3.0 mm (center), 6.0 mm (right)

ABOVETransient Mean Starboard Wheel Static Pressure Coefficient

ABOVEPressure spectra at the location of the Lower Door microphone

ABOVE¼-scale model of the Partially-Dressed Cavity-Closed (PDCC) Gulfstream G550 nose landing gear

This case was implemented as part of the Problem 4 of the First AIAA Workshop on Benchmark problems for Airframe Noise Computations (BANC-I), which was held in Stockholm, Sweden, on June 10-11, 2010. The geometry is a simplification of the Gulfstream G550 nose landing gear, configured as Partially-Dressed Cavity-Closed (pdCC). experiments on a quarter-scale model were performed in the NASA-BArT acoustic tunnel and at the University of Florida.

The computational model contained complete component details and resolved the geometry down into the laminar sub-layer (nominally y+ < 1). The mesh comprised trimmed hexahedra with extruded prisms in the normal-to-wall direction, totaling 39 million cells. In the vicinity of all the landing gear components and wheel, uniform cubic cells of 0.75 mm were used.

In addition, a mesh coarsening exercise was performed. Two coarse meshes were successively run, in which the cell size in the core flow region was increased from 0.75mm (fine) to 1.00 mm (medium mesh resulting in 22 million cells) and 1.25 mm (coarse mesh, 13 million cells), respectively.

First a steady-state simulation was performed in order to determine where volume mesh refinements were needed, as well as calculate the mesh frequency cut-off measure to size the cells. The applied mesh was well able to capture frequencies up to 5 kHz in the vicinity of the landing gear components, as shown on accompanying image.

The results from the transient compressible simulation, using DES and applying non-reflective treatments at the inflow and outflow boundaries, delivered a high level of confidence that both the mean and fluctuating flow fields were well predicted.

The total computational time for 0.25 seconds of simulated time on the fine mesh took approximately 16000 Cpu-hours on a modern 3.0 gHz Linux platform. This corresponds to just over 5 days on 128 CPUs. Likewise, the coarse 13 million cell case took just under 2 days. g

Case Study #1: Aeroacoustics of a Complex Nose Landing Gear

20 21 AEROREPORT

ABOVEmesh Frequency Cut-off estimator along the model center-line

ABOVEMean two-dimensional (x-y) turbulent kinetic energy – STAR-CCM+ prediction (top) and PIV results (left)

ABOVETransient Mean Static Pressure Coefficient on the Wheel


In this case study, we demonstrated the up-front use of the steady-state turbulence synthesization method to improve the noise signature of an avionics cooling rack. The electronics sit on shelves which are actively cooled by air channels within the shelving, supplied by ducts which are fed from the Environmental Control System (ECS).

debatin’s technique [1] was used to modify the original designs of plenum and shelf flow restrictor. The effects of the modifications were then assessed by quantifying the noise reduction through CFd simulation and comparing the results with the measured noise reduction. A DES simulation was used for the transient flow-field predictions. Microphones were placed in arbitrary location in the plenum and in the shelf restrictor.

It was found that the modified plenum design significantly reduces the volume of flow recirculation, and consequently the shear-noise generating mechanisms. The result was a reduction of noise levels across the full range of the human hearing spectrum. The DES simulation succeeded in predicting the level of noise reduction correctly (approximately 3dB in the range 300-10,000 Hz), but over-predicted the improvement in the lower frequency range.

The flow turbulence through the shelf restrictor was found to be greatly reduced, resulting in a 2-5 dB reduction is noise levels between 100 and 10,000 Hz. The predicted levels of noise reduction were excellent across this full range.

The total model size was approximately 1.5million cells. Calculations in steady-state and transient (DES) were performed by a graduate intern student and completed within a period of 3 months, using computer resources limited to 8 CPUs maximum.

Conclusion By working closely with the transport industry, CD-adapco provides validated tools to predict and design against aeroacoustical effects early in the design process. Two industrial aeroacoustics case studies, among a multitude of other possible applications in the aerospace industry, have been briefly described in this article. The results proved to be accurate and the study helped illustrate how a deeper understanding of acoustical phenomena can be gained through the use of STAR-CCM+, thereby enabling a higher degree of engineering value to be added while reducing costs and timescales in the CAE process.

For more information about methodologies and best practices for aeroacoustics simulations in the automotive and aerospace sectors, please refer to [2]. <

i Keep up TO dATe WiTH THe LATeST STAr-CCm+ reLeASe: www.cd-adapco.com/products/star_ccm_plus

reFereNCes:

[1] “Chasing Noise with Simulation”, Debatin, ECOMAS CFD 2006, The Netherlands,

September 5-8, 2006

[2] “Efficient CFD Simulation Process for Aeroacoustic Driven Design”, Mendonça et al., presented

at the II SAE Brazil International Noise and Vibration Congress, October 17-19, 2010, Florianopolis,

Brazil, SAE-2010-36-0545

BELOWMean z-wise vorticity – STAR-CCM+ prediction (left) and PIV results (right)

Case Study #2: Noise Signature from an Airbus Cockpit Avionics Cooling Rack

BELOWMean streamwise velocity component – STAR-CCM+ prediction (left) and PIV results (right)

22 AEROREPORT


ABOVE(Mean) transient (DES k-ω-SST) (left) and steady-state k-ω-SST (right)

ABOVE & LEFTAcoustic Pressure (Pa) at the driver’s ear location for the three different materials

www.cd-adapco.com/industries/aerospaceVisit the link below for more Aerospace stories:

ABOVE & LEFTPlenum noise reduction due to modified design (vertical grading corresponds to 2dB)

ABOVE & LEFTShelf restrictor noise reduction due to modified design (vertical grading corresponds to 1dB)

0 100 1000 100000 100 1000 10000

Delta db DESDelta db Experiment

Delta ESDelta Experiment

22 23 AEROREPORT

Fif teen weeks! That ’s al l i t took for a group of senior undergraduate students from the Universi ty of Washington’s Aerospace Engineering department to design, test , and bui ld a commercial qual i ty small Unmanned Aerial Vehicle (UAV) for research focusing on low-speed f l ight characterist ics and engine noise-shielding of supersonic f l ight vehicle configurat ions.

Dr. eli Livne, Professor of aeronautics and astronautics at the university of Washington, has been leading the senior capstone design project for more than a

decade with the help of Chester (Chet) Nelson, an affiliate associate Professor and a boeing technical Fellow. the motivation for the program was to provide students with ‘a complete, deep design experience’.

In the 2010 academic year, the goal of the project was to design, analyze, build, ground and flight test a UAV representing a commercial supersonic aircraft configuration, with focus on low speed handling characteristics, low sonic boom design, and noise shielding of the jet engine. Armed with just mission requirements and the design challenges for 2010, the team of seniors from the Aeronautics and Astronautics department of the University of Washington surpassed all expectations with a finished prototype that was one of the most complex and sophisticated of its kind. The project was completed within schedule and to budgetry constraints that would impress any aerospace industry leader.

Students with no previous CAE/Testing/Manufac-turing experience were given four months to develop the design into a flying prototype. If it sounds challenging, it is! The team of 32 seniors was split into groups which were tasked with: Computer Aided Design (CAD), aerodynamics and Computational Fluid Dynamics (CFD), wind tunnel testing, stability and

control, propulsion, acoustics, systems, structures, weight & balance, and construction. Over the course of the project, the students had the opportunity to experience and gain insight into major elements of the design process in the real world: teamwork, information exchange and communication, systems engineering, multidisciplinary interactions, and more. In short, this was the complete aircraft design experience. The University of Washington’s program is also notable for its industry participation. Local companies like Boeing, Aeronautical Testing Service (ATS), Fiberlay, the University’s low speed Kirsten Wind Tunnel, and local model airplane experts participate and donate materials, funds, time and guidance. CFD in early design phase The focus of this article is the CFD analysis that was conducted as part of the early design phase. One of the challenges of the CFD team was to learn the basics of CFD and how to use STAR-CCM+ to perform a thorough computational analysis, providing inputs for the initial design and eventually improving it. The fact that STAR-CCM+ is both easy-to-use and has many automation capabilities ensured bottlenecks in the simulation process were easily avoided. STAR-CCM+ was used for a series of planform studies, initially to find the base planform design that would be extensively tested in the wind tunnel.

In total, 34 different configurations were analyzed from a total of 274 CFD runs for 300 total man g

..::Feature artICLe Academia

From Design Challenge to Flying uaVs in Fifteen WeeksPrashanth shankara, CD-adapco

ABOVEInitial planform designs studied

ABOVESTAR-CCM+ results for CM vs alpha

24 AEROREPORT


ABOVEPolyhedral mesh on full model of aircraft

Why Study A&A at the UW?

The Aerospace Engineering industry is at the forefront of revolutionary technological developments in transportation, exploration, and national security, with new and significant challenges emerging every day.

The Department of Aeronautics and Astronautics at the University of Washington wants to help meet those challenges by offering bachelor’s, master’s and doctoral degrees that prepare students to become leaders in this exciting field. Our program is at the forefront of current research in space-based information systems, energetics, complex autonomous systems, composite materials, and more, ensuring our graduates will be competitive in academics and industry well into the future.

24 25 AEROREPORT


hours and 22,500 computing hours. These are impressive numbers! All CFD simulations were conducted on a 96 core Linux cluster at ATS. STAR-CCM+, CD-adapco’s finite volume based solver, was used for simulating fluid dynamics and to provide realistic inputs to the design of the final model. Half and full model cases were run after the preliminary planform studies to select the final configuration. Detailed simulations were then run to design the engine nacelle.

Design study Three of the initial planform designs are shown (previous page), with the plate representing the trunnion plate of the 2009 University of Washington’s Capstone UAV wind tunnel model, which was to be used as a base for the planform design. The wing names refer to the sweep angles of the inboard and outboard leading edges, respectively. STAR-CCM+ has been extensively validated for external aerodynamics and that confidence in the code translated to initial design studies being conducted solely in CFD. A polyhedral mesh was created for the half & full models with nearly 1.3 million and 4 million cells, respectively. The k-є turbulence model was used. Of all configurations studied, the 56-40 planform was chosen for further study in the wind tunnel. The CFD results (accompanying images) showed that the 56-40 configuration had a pitch-up problem from 6 to 15 degrees of angle of attack due to outboard wing stalling.

To eliminate the pitch-up problem, two different configuration modifications were studied, the first involving adding a chine and the second using a dogtooth wing. Although the addition of a chine was theoretically expected to remove the pitch-up problem, results from STAR-CCM+ showed that the chine created a vortex and outboard wing separation at 12 degrees angle of attack. At 20 degrees, the entire outboard wing had stalled and parts of the inboard wing showed separation too. A dogtooth wing was attempted next with the dogtooth sized to 7% of the wing chord. This design showed improvements in pitching and lift over the base case but still didn’t solve the pitch-up problem. Eventually, this was left for wind tunnel tests.

The image opposite (middle) shows the CFD results for the 2010 base case, 2010 V-Tail planform and the 2009 wind tunnel data for the 2009 V-Tail configuration. The final tail design for the 2010 UAV included horizontal and vertical tails. Nearly 25 different configurations were simulated in

ABOVEStreamlines behind the wings

26 AEROREPORT

ABOVECl vs alpha for the V-Tail configuration - Comparison of STAR-CCM+ (CFD) and wind-tunnel (WT) results

ABOVECm vs alpha in the final cruise configuration - Comparison of STAR-CCM+ (CFD Cruise) and wind-tunnel (WT Cruise) results

ABOVECd vs alpha in the final cruise configuration - Comparison of STAR-CCM+ (CFD Cruise) and wind-tunnel (WT Cruise) results


ABOVE + BELOWStreamlines from STAR-CCM+ showing aircraft with Chine at different angles of attack

CFD to optimize the initial wind tunnel model. After the wind tunnel tests were completed, the final configuration was simulated once again using STAR-CCM+. The results of this verification simulation showed excellent comparison with wind tunnel data over a wide range of angles of attack as seen in the adjoining graph. The cruise conditions of the aircraft were well captured by CFD. Finally, the effect of wind tunnel walls was also simulated in STAR-CCM+ to allow comparison of wind tunnel and free flight characteristics.

One of the most important lessons learned from the Capstone project was that CFD and Wind Tunnel Testing are integral parts of the design cycle and are complementary to each other. Alex Lacomb, CFD Lead for the program, said,

“STAR-CCM+ has the easiest GUI I’ve experienced in a CFD code, in addition to the easy automated meshing which made the tool very valuable to the design team.” The aircraft was successfully flight tested last summer and bears testimony to the excellent work of the students at the University of Washington’s Department of Aeronautics & Astronautics. CD-adapco is proud to be associated with such a rewarding research program for undergraduate students. <

i mOre iNFOrmATiON ON THe uNiVerSiTY OF WASHiNgTON’S ACAdemiC AerOSpACe prOgrAmS: www.aa.washington.edu/

What we couldn’t do in previous years of the program with other codes was made possible with STAR-CCM+. We were able to run hundreds of high-end CFD analyses in 4-5 weeks by a group of seniors who before that had had no experience with commercial CFD.

26 27 AEROREPORT

Virtual Design enables a revolutionary Flying technology to take offDavid Lasserre, eNteCHO

www.cd-adapco.com/downloads/special_reportsAerOSpACe SpeCiAL repOrT iSSue 1 CAN Be dOWNLOAded Here:

..::Feature artICLe VTOL

28 AEROREPORT

The virtual design environment approach has provided an early and thorough understanding of the potential and capabilities of this innovative flight technology.


CFD Techniques The design process started with a searching aerodynamic analysis in order to establish the best interaction between the lifting surfaces and to set the parameters of the propulsion system that satisfy the lift requirements. during the concept creation stage, no prototype was built, and the geometry development relied only on the CFD results. To ensure a high turnover of results for each configuration, automation scripts were written to create, mesh and run a matrix of geometries and boundary conditions. In the next step where the flight mechanics and stability are analyzed, all surfaces relevant to the control of the craft are modeled in detail. However, to reduce the complexity, rotor and stator blades are simulated through a momentum generator, using the user subroutines capability of STAR-CCM+.

The radial momentum added to the system converges on the value of the power input needed to hover in each case. An additional swirl can also be added to accurately simulate any residual tangential flow. The mesh generation and model setup is controlled by a script that implements the CD-adapco automatic meshing feature when running a series of cases at different control surface configurations and flight orientations.

The flight control system analysis has proved essential in the optimization of the performance of the attitude control system. For example, the flight performance of the manned platform in particular required detailed analysis of its behavior in ground effect. This flight control system analysis returns accurate aerodynamic forces and pitch, roll and yaw torque inputs to the flight control system lookup tables, with up to four configurations being run daily on the solving cluster. g

The challenge of designing a next generation compact Vertical Take Off and Landing (VTOL) craft has been addressed with the combination of a novel radial fan technology and the use of unique lift ing and control surfaces.

28 29 AEROREPORT

BELOWMomentum model, tilted flight

Simultaneously, the propulsion system and lifting surfaces are analyzed in greater detail. Sector meshes are set up for the Moving Reference Frame (MFR) method to analyze the propulsion turbo machinery. Special attention is paid to the rotor and stator interactions with the blades optimized to satisfy the dual requirements of efficient lift generation and rotor torque cancellation.

During the same design loop, the yaw control surfaces capabilities can be evaluated in order to complete the range of information needed for the flight control system. Mesh size and setup parameters have been optimized to allow at least one configuration to be run overnight. This stage closes the aerodynamic design loop, as shape and dynamic loads are then known for the CAD/FEM team to finalize the model.

Benefits and AchievementsThe STAR-CCM+ simulation process is fully integrated into the virtual design process and interacts strongly with the CAD design and software development for the control system. The design loads predicted by the CFD analysis make the choice of the composite materials in the craft’s structure much easier, leading to significant weight reductions and further improvements in the payload and endurance capabilities of the flight platform.

The flight control system CFD analysis has proven to be a powerful tool. One of its most important outputs is the data that is fed into a flight simulator that delivers realistic attitude response and lift characteristics. It has also made it possible to identify, quantify and address an unusual ground effect response and therefore avoided putting the prototype craft or personnel at risk. Once the CFD calculations of aerodynamic

performance and attitude control met the prerequisite targets, a prototype flight platform was constructed.

The successful test flights of this “MuPod” UAV (Unmanned Aerial Vehicle) has confirmed the value of CD-adapco products in providing accurate flight characteristics early in the development process. It was very rewarding to witness the technology at work as the prototype took off for the first time and behaved as predicted by the flight simulator.

Evolution The virtual design environment approach has provided an early and thorough understanding of the potential and capabilities of this innovative flight technology. The number of hardware variants selected for construction has been reduced significantly by using the right tools and the right techniques and significant savings in time and cost have been realized as a result. We are currently updating the implementation methodology to use STAR-CCM+ with very promising results so far. <


RIGHTMFR method, flow through the rotor

❐ COMPANY PROFILE

Advanced Flight Technology

Entecho was formed for the purpose of commercializing the unique

flight technology that founder Kim Schlunke developed.

Kim’s dream was to make the world a better place, ultimately by

producing a flying vehicle that could partially replace road travel,

thereby reducing congestion and pollution.

i FOr mOre iNFOrmATiON ABOuT eNTeCHO ViSiT: www.entecho.com.au

30 AEROREPORT

ABOVEUsing an axis symmetric mesh provides the best compromise of quality, density and size


30 31 AEROREPORT 31 AEROREPORT

..::star-CCM+ Applications

32 AEROREPORT

star-CCM+ for aerospace applicationsadvanced Numerical Physics:

• AChoiceofsolversthatprovideaccurateandefficientsolutionsacrossallspeedregimes.

- Coupled implicit / coupled explicit (density-based)

- Segregated implicit (pressure-based)

• Automaticpreconditioning

• Fullsuiteofturbulencemodels

- (1-equation,2-equation,RSM,LES,DDES,etc.)

• Automatichybridwallfunctions

• Boundarylayertransition

• Multi-speciesflows

• Eulerian/Lagrangianmultiphase

• Freesurfaceflows

• Thinfilms

• Porousmedia

• Frozenrotor

• Slidinginterfaces

• Moving/deformingmeshes

• 6DOFmotion

• Oversetmesh

• Multiplereferenceframe

• Conjugateheattransfer

• Reactingflows

• Acoustics

extensive Industry application:

• Environmentalcontrolsystems

• Plumeanalysis

• Reentryflows

• Rotorcraft

• Anti-icing

• Aeroacoustics

• Aeroelasticity

• Combustion

• Inlets/nozzles

• Externalaerodynamics

• Rotatingmachinery

• Thermalmanagement

• Launchsystems

• Electronicscooling

• Hydraulicsystems

• Storeseparation

• Rocketmotor

• Fuelsystems

• Tanksloshing

• High-lift

• Andmore!

32

unrivaled Meshing technology:

• Advancedsurfacewrapping

• Manualandautomaticsurfacerepairtools

• Parallelizedmeshing

• Generalpolyhedralmeshes

• Automatichexadedralmeshes

• Prismaticextrusionlayermeshes

Powerful Visualization & Post Processing:

• Parallelizedpost-processing

• Visualizestreamlines,vectors,scalars,iso-surfaces,andmore

• Line,surface,andvolumeintegrals

• Reportsandlineplots

• Liveupdatesduringsolution

Designed for Multi-Physics:

• Batteriesandelectricmachines

• Built-infinite-volumestressmodel

• Fluid-structureinteraction

• Co-simulation

Modern software architecture:

• Singleintuitiveuserenvironment

• CAD-embeddedinterfaces

• Client-serverbasedarchitecture

• Monitor/modifyrunningjobs(includingbatchjobs)

• Extensiveautomationcapabilities

• Efficientparallelization

..::star-CCM+ Applications

accuracy efficiency Flexibility reliability robustness Productivity

www.cd-adapco.com/products/star_ccm_plusFOR MORE INFORMATION ABOUT STAR-CCM+ VISIT:

31 AEROREPORT 33 AEROREPORT

Follow us online.For more information: [email protected] www.cd-adapco.com

• STAR-CCM+ • STAR-CD • Engineering Services • Dedicated Support

simulation software for a New Frontier in engineering Innovation

aerOsPaCe sPeCIaL rePOrt - MDXmdx2.plm.automation.siemens.com/sites/default/...02 aerospace report Introduction by Deryl Snyder aerOsPaCe ... associate editors Prashanth Shankara -

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