OpenVSP with AVL

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Aeronautical Sciences Project

OpenVSP with AVL

Erik D. Olson NASA-Langley Research Center

OpenVSP Workshop v3 Aug. 22, 2014

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Aeronautical Sciences Project

Outline

• NASA EET AR12 Model

• Flap Modeling

• OpenVSP to AVL Conversion

• Validation Results

• Degenerate Geometry

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Aeronautical Sciences Project

NASA EET AR12 Model

Morgan, H.L. and Paulson, J.W.: NASA TP-1580 (1979) L-78-1654

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Aeronautical Sciences Project

NASA EET AR12 Model

• Langley 14x22 Wind Tunnel ca. 1978

• 12-foot span supercritical wing

• Full-span slats

• Part-span double-slotted flaps with cutout

• Moveable horizontal tail

• Flow-through nacelles, landing gear

• Morgan, H. L.: NASA TM-80048 (1979) and Morgan, H.L. and Paulson, J.W.: NASA TP-1580 (1979)

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Aeronautical Sciences Project

EET AR12 OpenVSP Model

• Planform shape from configuration description

• Wing airfoils from tabulated coordinates

• Fuselage sections digitized from plotted cross sections

• No nacelles, gear or gear pod

• Wing twist added to Hermite export file using external utility

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Aeronautical Sciences Project

Flap and Control Surface Layout

Constant-chord double-slotted flap (30% chord at e=0.383)

30% chord double-slotted flap

15.5% chord slat

15.5% chord slat

h = 0.096

h = 0.97 h = 0.97

h = 0.97 h = 0.71

h = 0.45

h = 0.383

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Aeronautical Sciences Project

Modeling of Flap Effects

• In practice, the theoretical lift increment from linear theory cannot be realized

– inadequacy of linear theory at large flap angles

– viscous effects

– flow separation at large flap angles

• Apply a flap effectiveness factor, 𝜂𝛿

• Account for slotted flap chord extension

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Aeronautical Sciences Project

Slotted Flap Effectiveness

Single-slotted Double- and triple-slotted

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Aeronautical Sciences Project

Empirical Chord Extension Ratios

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50 60

Dc

/ c f

Flap deflection, deg

single-slotted

double-slotted w/ fixed vane

double-slotted (variable geom)

Fowler, single-slotted, double-slotted w/ fixed vaneFowler, double- and triple-slotted

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Aeronautical Sciences Project

Athena Vortex Lattice (AVL)

• Open-source (GPL) code developed at MIT (Drela & Youngren)

• Forces and moments, trim, steady rotation

• Stability derivatives w.r.t. angles, rotation, control surfaces

• Rigib-body, quasi-steady eigenmode analysis

• Incidence, camber, and control-surface or flap deflections modeled as normal-vector tilt only

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Aeronautical Sciences Project

OpenVSP to AVL Conversion

• Uses OpenVSP Hermite (Xsec) file export with external HRM2AVL utility

• AVL lifting surface sections (leading-edge coordinate, chord, incidence) calculated from Hermite cross sections

• Lifting-surface sections converted to normalized airfoils camberline determined by AVL

• Cruciform fuselage interpolated from Hermite cross sections

• Flap chord extension built into model

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Aeronautical Sciences Project

Cruise Wing

Takeoff Flaps

EET AR12 AVL Model

Uncambered wing carry-through

Segmented panels with local cosine spacing

Cruciform fuselage

Flap chord extension

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Aeronautical Sciences Project

0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

CL

CD

AVL (ideal)AVL + DATCOMAVL + XfoilData

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24

Cm

angle of attack, deg

AVL (ideal)AVL + DATCOMAVL + XFoilData

Cruise Wing Validation Results

Mach 0.168, Rec = 1.37x106

0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24

CL

angle of attack, deg

AVL (ideal)AVL + DATCOMAVL + XFoilData

XFoil CL,max = 1.79

• Actual 𝐶𝐿,max = 1.34

• Predicted 𝐶𝐿,max (XFoil) = 1.79 (+33%)

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Aeronautical Sciences Project

Takeoff Wing Validation Results

0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24

CL

angle of attack, deg

AVL (ideal)

AVL + DATCOM

Data

Cruise Wing Data

0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

CL

CD

AVL (ideal)

AVL + DATCOM

Data

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24

Cm

angle of attack, deg

AVL (ideal)

AVL + DATCOM

Data

Mach 0.168, Rec = 1.37x106

• Actual 𝐶𝐿,max = 2.51

• Predicted 𝐶𝐿,max (Xfoil + empirical Dcl,max) = 2.41 (-4.0%)

XFoil CL,max = 2.41

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Aeronautical Sciences Project

Landing Wing Validation Results

Mach 0.168, Rec = 1.37x106

0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24

CL

angle of attack, deg

AVL (ideal)

AVL + DATCOM

Data

Cruise Wing Data

0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

CL

CD

AVL (ideal)

AVL + DATCOM

Data

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24

Cm

angle of attack, deg

AVL (ideal)

AVL + DATCOM

Data

• Actual 𝐶𝐿,max = 2.82

• Predicted 𝐶𝐿,max (Xfoil + empirical Dcl,max) = 2.77 (-1.8%)

XFoil CL,max = 2.77

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Aeronautical Sciences Project

OpenVSP v3.0 Degenerate Geometry

OpenVSP Model Plate Export