actiflow

Delft, November 4th 2010

Actiflow: Using OpenFOAM Technology for Aeroconsulting

OPENFOAM is a registered trade mark of OpenCFD Limited, the producer of the OpenFOAM software

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Today the following items will be presented to you

Actiflow: an engineering company with a focus on aerodynamics The reasons why Actiflow chose OpenFOAM as the main CFD solver Examples on the use of OpenFOAM by Actiflow

Development of steady state electrohydrodynamics solver ehdFoam Active automotive aerodynamics Other examples of the use of OpenFOAM within Actiflow

Introducing CFDDesk, the Dutch OpenFOAM support system Concluding remarks on OpenFOAM technology as used within Actiflow

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Actiflow is an engineering company with a focus on aerodynamics

Actiflow is founded in 2005 as a spin-off of Delft University of Technology We offer various services:

Design Engineering (including prototyping and testing) Aero Consulting

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Actiflow is young and dynamic, providing accurate and fast results

Actiflow is flexible and thinks with the customer We are experienced in a large range of fluid flow problems We can perform several tasks in the design and prototyping phases and assist product

development Next to computational facilities we also have experimental facilities in our workshop

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Actiflow chose OpenFOAM technology based on several characteristics

OpenFOAM is open source and allows parallel calculations without licensing costs OpenFOAM is, generally speaking, as accurate as or even better than commercial CFD

codes Solvers can be modified for specific needs Special boundary conditions and applications can easily be created and implemented Full control over the solving algorithms without hidden filters and limiters Large amount of models, algorithms and solvers are available State of the art development work is going on all around the world Assistance with common problems via the forum

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A solver for steady-state electrohydrodynamics, ehdFoam, was created in order to model an innovative air purifier For one of the customers, Virus Free Air (VFA), a new solver had to

be created Their innovation is an electric air purifier based on corona wind There was a need to compute the flow of charged particles in the

design stage of the electronic air purifier In order to model this flow a solver was created based on available

solvers: electroStaticFoam and simpleFoam To model the corona wind effect a new boundary condition, corona

discharge boundary is created: Several types are created, depending on the application and

conditions For post-processing the Lagrangian particle solver was modified to

the electrostaticParcelFoam, which calculates particle paths of charged particles in an electrically charged fluid influenced byelectrostatic forces, gravity, buoyancy and drag

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ehdFoam, solver for steady-state electrohydrodynamics

Source: N. E. Jewell-Larsen et al., Modelling of corona-induced electrohydrodynamic flow with COMSOL Multiphysics, ESA Annual Meeting on Electrostatics, 2008

Corona discharge is defined as the electrical discharge brought on by the ionization of a fluid surrounding a conductor, which occurs when

the electric field strength exceeds a certain value.

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The model uses these equations, involving two-way coupling of fluid and electric field

Continuity

Momentum

Turbulence Modeling

Gauss law

Conservation of charge

( )

( )

2

2

0

from turbulence model

01

0

t C

t

C

C e C C

u

pu u u E

V

J E u D

=

= + + +

=

= + + =

Electrostatic body force

Convection of charge density

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The model equations are implemented in ehdFoam as follows

Pressure-velocity coupling uses the SIMPLE algorithm

Turbulence is modeled using the OpenFOAM RAS models

Electrostatic equations are solved before the SIMPLE loop

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The electrostaticParcelFoam model equations are defined similarly

Location of particle

Forces acting on the particle Aerodynamic force (drag only)

Electrostatic force

Gravitational force Buoyancy force

(

( )

0 0

' '

' 0 0

2

3

( )( ) '

( )2

43

s t s sp

p p pps s

p D E g b

DD p p

E p

g p

b p

F sx t x u ds ds

m

F F F F F

C Re rF u u u u

F Eq

F m g

F r g

pi

pi

= =

= =

= + +

= + + +

=

=

=

=

Particle charge needs to be determined

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The electrostaticParcelFoam model equations are defined similarly

Saturation charge

Current charge, if q(0)=0

Time needed to reach 0.5 qmax from q(0)=0

Substitution, q(t*)=0 (definition)

New time derivative to be used( )

2max 0

max

0

*

max

max

2*

4 p

( )1

4

q r E

qq t

tE

Jq

tq q

qqt t

pi

=

=

+

=

=

=

+

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The first test case was a 2D Wire Flow

Validation of the solver, comparison with an experiment and simulation with COMSOL(N. E. Jewell-Larsen et al., Modelling of corona-induced electrohydrodynamic flow with COMSOL Multiphysics, ESA Annual Meeting on Electrostatics, 2008)

Single coronating wire with 14 collecting wires Coronating wire potential: 8000 V Collector wires potential: 0 V

Jewell-Larsen et al. ehdFoam

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The results of the test case are satisfactory

The final goal of the solver is accurate prediction of the flow field due to corona discharge

The solver recreates the electric, charge density and velocity fields that were observed in the paper during computation and experiment

Jewell-Larsen et al. ehdFoam

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The solver and postprocessing utility where later applied to an actual design The objective of the solver was an actual application of corona wind in an air filter

Challenging 3D Case: very small needles, rather large domain

Circular tube, with carefully placed needles

Movie shows charged particles enter a filtering tube and how they are affected by the electric and velocity fields

Air is sucked into the tunnel due to corona discharge effect Particles are effected by the charged needles and secondary flow is induced

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The base of Actiflow is automotive application of active aerodynamics

Actiflow applied boundary layer suction on: Formula Renault front wing Ferrari F430 diffuser

Using OpenFOAM, Actiflow simulated boundary layer suction on: Bluff body equipped with a diffuser Ahmed Body Several commercial car models

Using OpenFOAM, Actiflow simulated base bleed on: Ahmed Body VW Golf V Several other commercial

car models

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A procedure for active aerodynamics analysis was developed

The procedure starts with analysis of the flow around the standard geometry The flow field is investigated and the geometry is adapted for base bleed and suction

panels Without flow control, the simulation is carried out again, to check the consistency Active flow control simulations are carried out to find promising configurations

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Results obtained with the Ahmed body are promising

With a parameter variation, the configurations can be optimized for drag reduction or lift reduction/downforce increase

Using an optimal design the lift of the body can also be influenced positively Finally there are geometrical design loops incorporating the active flow control system

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OpenFOAM results for active automotive aerodynamics are within engineering accuracy and fast Remarks considering the accuracy of the results are the following:

The correct trends are captured No cooling flow, simplified wheels, cleaned geometry Simulation of bluff body flow remains challenging for RANS Actiflow is investigating LES/DES, but it is not yet applicable in design loops Simulations are good for conceptual design, road/wind tunnel tests are used for the

final design

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Actiflow is active in different fields of application

Our main fields Automotive Wind Energy Building Physics Medical

Other

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Actiflow uses OpenFOAM for several other flow phenomena

Building Physics: Wind hindrance HVAC design

Office Buildings Church renovation

(Conjugate) Heat transfer Heat flux sensor design Heat transfer with floor heating

Medical solutions Innovative infant incubator

Wind energy Development of small wind turbines Active flow control on large scale wind turbines

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Actiflow uses OpenFOAM for several other flow phenomena

Ship hydrodynamics: Investigation into the occurrence of cavitation

Turbomachinery: Pumps, ventilation systems

Consumer goods: Senz Umbrellas

Smoke and toxic contents dispersion Welding smoke: Clean Air Diesel generator exhaust fumes Factory planning

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Setting up Dutch OpenFOAM support desk for other companies

Together with Vortech, Actiflow offers the possibility to set-up OpenFOAM support for other companies

Several levels of support will be created First line support: Fast response for small problems (telephone/email) Second line support: In depth analysis of the problem, may take more time

Consultancy is another option: We help decide whether the use of OpenFOAM is beneficial Support with installation, updating and organization

Development of solvers and utilities for specific problems Advice on model choice and solution method With the experience of Vortech and Actiflow, the steep learning curve becomes more

gentle The support system is still young, so any comments will be appreciated More information can be gathered at Vortechs and our stand and in the flyer

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The website will be used as a portal for support and is online

http://www.cfddesk.nl/

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Concluding remarks on the use of OpenFOAM for aeroconsulting

Due to the versatility of OpenFOAM, Actiflow can consult a large variety of customers After several years of experience we have confidence in our simulations and the solutions

to problems we solve The open source format allows to create or adapt models as needed and helps

understanding the working method of the software With OpenFOAM we can accurately solve complex problems from different fields within the

timeframe of an engineering design process With our experience we can help others start enjoying the many benefits of OpenFOAM

Actiflow BVZinkstraat 22

4823 AD BredaThe Netherlands

[email protected]

Tel: +31 765 422 220

actiflow

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