1 VSPAERO Verification Testing -...

NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sep. 1st

1

Empirical Systems Aerospace, Inc. www.esaero.com

VSPAERO

Verification Testing

Presented by:Lucas Payne

Empirical Systems Aerospace, Inc.


2


Agenda

• Introduction• Approach

– Previous Studies/References• Test Cases Overview• Test Case

– Methodology• Geometry setup• Test Setup

– Results• Errors


3


Problem Statement

• VSPAERO is a relatively new solver with few authoritative verification studies

• VSPAEROs rapid feature development and capabilities are not supported with verification artifacts


4


Introduction

• Objective:– Verify VSPAERO results with comparisons to

authoritative theoretical and empirical solutions– ID bugs in UI/solver– Develop verification toolset– Document best analysis practices

• Requirements:– Ability to automate– Immediate plotting of results– Control of features that impact solution quality & speed


5


Approach


6


Other Studies/References

• VLM manual for Surfaces – Used similar testing cases

• Hershey-Bar Wing• Swept Wing• Warren-12

• Dave Kinney, Workshop 16’– High AR Wing– Supersonic Delta Wing


7


Test Rational

Completed:

Hershey-Bar Wing Easy to re-create in OpenVSPEmpirical solutions available

Swept Wing & Bertin-Smith Wing Easy to re-create in OpenVSPEmpirical solutions available

Warren-12 Wing Easy to re-create in OpenVSPEmpirical solutions available

Von Karman-Trefftz Airfoil Easy to re-create in OpenVSPExact 2D solution available

Testing CP slicer

Planned:

Ellipsoid Easy to re-create in OpenVSPExact solutions available

Cessna 172Empirical solutions available

Test Case Overview


8


Hershey-bar Wing: Methodology

• Method: VLM• Compare to:

– 2D Theory (2p)– Lifting Line Theory

𝜕𝛼𝜕𝐶$

≈ 10 +9𝐴𝑅, +

20𝐴𝑅

Parameter Min Max N-PtsAR 5 60 12

N-Span 6 100 5N-Chord 20 110 5

Tip Cluster 0.1 1 3

Test Matrix: 900 Unique variations

Default Clustering: LE = 0.25, TE = 0.25, Root = 1

Hoerner (1992)


9


Hershey-bar Wing: Results

Ave % Diff of VSP to LLT: -2.2 %

% Diff of AR60 to thin Approx (2p): -8.9 %

Run from: OpenVSP v3.13.1VSPAERO v4.1.1

Default Clustering: LE = 0.25, TE = 0.25, Root = 1, Tip = 1Default Tessellation: N-Chord = 33, N-Span = 6

Run conditions: AOA = -20, -15, -10, -5, 0, 5, 10, 15, 20°

M = 0.1

% Dif = 100*(est-truth)/truthest = CLa(VSP)truth = CLa(Calculated from LLT)


10


Hershey-bar Wing: Results – Grid Study

Clustering: LE = 0.25, TE = 0.25, Root = 1, Tip = 0.2

% Dif = 100*(est-truth)/truthest = CLa(VSP)truth = CLa(Calculated from LLT)


Run conditions: AOA = 1°M = 0.1


11


Hershey-bar Wing: Results – Grid Study

𝐴𝑅.. =

0.5 ∗ 𝐴𝑅𝑆𝑝𝑎𝑛𝑇𝑒𝑠𝑠 − 1

𝑐𝐶ℎ𝑜𝑟𝑑𝑇𝑒𝑠𝑠 − 1

2 Run from: OpenVSP v3.13.1VSPAERO v4.1.1


Clustering: LE = 0.25, TE = 0.25, Root = 1, Tip = 1


12


• Method: VLM• Compare to:

– 3D theoretical


N-Span 6 100 5N-Chord 20 110 5

Tip Cluster 0.1 1 3


Swept Wing: Methodology

𝐶$@ =2𝜋 ∗ 𝐴𝑅

2 + 𝐴𝑅,𝛽,k, 1 +

tan, LF/,𝛽, + 4

�

AR = Aspect Ratioβ = Mach parameter = 1 −𝑀,� , M = 0.1k= Ratio of 2D CLa to 3D CLa, 1 for theoreticalLF/,= Sweep at 50% chord

Default Clustering: LE = 0.25, TE = 0.25, Root = 1

Lowry and Polhamus (1957)


13


Swept Wing: Results

% Dif: +3.8%

*Tessellations: N-Chord = 80, N-Span = 6;




14


Swept Wing: Methodology – Case 2


Sweep 5 40 8


*Same Clustering: LE = 0.35, TE = 0.65Default Root/Tip Clustering = 1

Goal: Test how sweep changes accuracy of solution


15


Swept Wing: Results

*Tessellation: N-chord = 80, N-span = 6

*Tessellation: N-chord = 60, N-span = 20



*Same Clustering: LE = 0.35, TE = 0.65Default Root/Tip Clustering = 1


16


Bertin-Smith Wing: Methodology

• Published data• VLM• Comparisons made

between CLa.– Tessellations:

N-Chord = 61 N-Span = 7

Great OWL Publishing (2009)


17


Bertin-Smith Wing: Results

• Published results are: CLa = 3.433 /rad

• VSPAERO Results: CLa = 3.204 /rad» % Diff: -6.7%




18


• Published data• VLM• Comparisons made

between CLa and CMa

– Tessellations:N-Chord = 61 N-Span = 7

Warren-12 Wing: Methodology

Great OWL Publishing (2009)


19


Warren-12 Wing: Results

• Published results:

– CLa = 2.743 /rad

– CMa = -3.10 /rad

• VSPAERO Results:

– CLa = 2.7473 /rad• % Diff: +0.16%

– CMa = -3.1495 /rad• % Diff: +1.6%




20


Von Karman-Trefftz Wing: Methodology

• Method: Panel• Compare to:

– Karman-Trefftz Transformation Solution– CP slicer

Parameter Min Max N-PtsEpsilon 0.1 0.2 3Kappa 0 0.2 5

Tau 5 20 4


Same AR = 30Same tessellation: N-chord = 70, N-span = 30Same Clustering: LE = 0.35, TE = 0.65, Root/Tip = 1


21


Von Karman-Trefftz Wing: ResultsRun from: OpenVSP v3.13.1

VSPAERO v4.1.1



22


Von Karman-Trefftz Wing: ResultsRun from: OpenVSP v3.13.1

VSPAERO v4.1.1



23


Von Karman-Trefftz: Methodology

Parameter Min Max N-PtsKappa 0 0.1 2N-Span 15 80 5N-Chord 15 80 5


*Same AR = 15Same Airfoil parameters: Epsilon = 0.1, Tau = 15Same Clustering: LE = 0.5, TE = 1.0, Root/Tip = 1

Goal: Test how tessellations impact CP slicer and the accuracy of solution


24


Von Karman-Trefftz Wing: Results





25


Von Karman-Trefftz Wing: Results





26


Karman-Trefftz Wing: Error Example

• Symptom: Erratic CP distribution at outer span• Cause: User error - Half mesh generation due to X-Z Symmetry• Status: Improvements made to make repeating this mistake more difficult

Before: After:


27


• Tool suite Features– Improved Automation– Add all plots/results to wiki– Add Scripts to future releases

• Next Tests– Ellipsoid– Cessna 172

Ongoing Work


28


1. Great OWL Publishing. (2009) Surfaces Vortex Lattice Module: User Manual

2. Hoerner, Sighard F., and Henry V. Borst. Fluid-dynamic Lift: Practical Information on Aerodynamic and Hydrodynamic Lift. N.p.: Hoerner, 1992. N. pag. 3-2. Print.

3. Lowry, John G., and Edward C. Polhamus. "A Method for Predicting Lift Increments Due to Flap Deflection at Low Angles of Attack in Incompressible Flow." NACA-TN-3911 (1957): 1-30. NASA Technical Reports Server. Web.

References:


29


Questions?


30


Contact Information

Lucas [email protected]

Date post:	19-Jul-2020
Category:	Documents
Upload:	others
View:	15 times
Download:	0 times

1 VSPAERO Verification Testing -...

Documents