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Interacuve Wave Drag in Openvsp

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Interacuve Wave Drag in Openvsp Interac(ve Wave Drag in OpenVSP (eta ~6mos) Rob McDonald Michael Waddington (MS July 31, 2015) Cal Poly Roadmap • Background: Wave Drag and OpenVSP – Problem & Solu(on • Wave Drag Evalua2on and Analysis – Leveraging the wave drag integral • Incorporang Wave Drag Evaluaon in OpenVSP – Building the wave drag tool • Tool Implementaon – Demonstrang use of the Wave Drag Tool • Analy2cal Comparisons – Verifying proper applicaon of wave drag evaluaon • Tool Demonstraon • Conclusion 2 Wave Drag Background • Drag experienced during transonic/supersonic flight due to presence of shock waves • Contributed to the false no(on that manned supersonic flight would à be impossible “sound aerospaceweb.com barrier” • Wave drag problemac for design of jet-powered military aircra • Rocket-powered Bell X-1 crossed sound barrier in 1947 • Shaped like a bullet 3 Wave Drag Background • Area-ruling technique independently discovered by Richard Whitcomb of NACA in 1952 – Manage cross-sec(onal area distribu(on to reduce wave drag • “Whitcomb area rule” salvaged Convair F-102 program 456fis.org 4 Exisng Tools • “Harris Wave Drag” code – Roy Harris, NASA LaRC – Used by NASA, Boeing – Fortran code publically available • Requires column input of geometry data • Inaccuracies from lack of component intersec(on capability • Mandatory X-Z plane symmetry • “AWAVE” – L. A. McCullers, NASA LaRC – Streamlined the Harris code – Not publically available 5 Wave Drag Theory z Momentum analysis: Aircra in control surface y Wave drag integral: x z y Far field perspec2ve: x Mach cone from control surface is planar at aircra. 6 Cross-Sec(onal Area Calculaon Slice aircra with Mach cung planes rotated about aircra axis Calculate resul(ng area projec2ons onto Y-Z plane Need the 2nd derivave for the wave drag integral NASA 7 eminton-Lord Wave Drag evaluaon • evaluate wave drag integral with Fourier series – elegant es(mate of of 2nd derivave of area – Uses addi(onal terms to find minimum wave drag shape for the given data • The standard method for wave drag es(maon – Used by Harris Wave Drag code and AWAVe – C code reimplementaon of eminton-Lord provided by Dr. Sriram Rallabhandi for use in this work 8 Maximum Wave Drag Contribu(on • Automacally finds maximum wave drag locaon along aircra axis – Maximum drag per cung plane rotaon – Maximum drag overall • GUI bumons “snap” area plot and cung plane visualizer to max drag locaon • Provides design intuion for wave drag migaon 9 Maximum Drag Contribu(on • Locaon of maximum drag contribu(on 0 −1 −2 −3 y| − ln|x −4 Reaches max magnitude as |x-y|à 0 −5 −6 −7 |x-y| à 0 as x à y 0 0.2 0.4 0.6 0.8 1 |x−y| Note: ln(0) singularity handled by THus, to pursue max magnitude, let x=y eminton-Lord 10 Maximum Drag Contribu(on • Locaon of maximum drag contribu(on 0 −1 −2 −3 y| − ln|x −4 If x=y, then S’’(x)S’’(y) = [S’’(x)]2 −5 −6 −7 Max magnitude occurs at max |S’’(x)| 0 0.2 0.4 0.6 0.8 1 |x−y| Max |S’’(x)| produces largest drag contribuon 11 Modeling engine Flow-Through • Two op(ons to account for flow-through components: Make component hollow: Use subsurface on a solid: – Not always prac2cal – Subsurface area must be for the user subtracted 12 Modeling engine Flow-Through 25 20 Inlet/exit 15 no(ceable in 10 Area steps 5 0 -5 0 0.2 0.4 0.6 0.8 1 x/L 25 Air not impeded 20 by flow-through 15 10 Area 5 Inlet/exit 0 projected area -5 0 0.2 0.4 0.6 0.8 1 13 x/L included Modeling engine Flow-Through Approach A Approach B Approach C 25 25 25 20 20 20 15 15 15 10 10 10 Area Area Area 5 5 5 0 0 0 -5 -5 -5 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 x/L x/L x/L • Inlet/exit projected • Inlet projected area • Linear combo of inlet/ area included subtracted exit area subtracted • Curve starts/ends at • Curve starts at zero, • Curve starts/end at non-zero may end at non-zero zero • S(x) shied by a • S(x) shied by a • S(x) shied by 1st constant constant order func2on of x 14 Modeling Flow-Through 25 3000 A A B B C 2500 C 20 2000 15 1500 10 1000 Area 500 5 Second Derivative of Area 0 0 −500 −5 −1000 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 x/L x/L • Wave drag depends on 2nd derivave of S(x) • Terms added in Approaches A, B, and C differen(ate to zero in S’’(x) • Iden(cal S’’ values à Idencal wave drag results • Approach C chosen so S(x) curve starts/ends at zero 15 Cung Plane Procedure • Start/end cung planes determined automacally • ensures full capture of the aircra Tangent Start Cut Tangent end Cut 16 Cung Plane Procedure • Set of planes constructed for each theta – Rotated to theta, rotated to Mach angle, and translated along x-axis • Planes intersected with aircra • Projected intersec(on areas are calculated 17 Subsurface Modeling of Flow-Through 18 Handling Flow-Through Select all flow face subsurfaces in +x Wave Drag GUI x -x +x Normal vectors determine inlet or exit Flow face extended 19 Handling Flow-Through 20 eminton Lord Soluon 25 20 eminton-Lord solu(on used to 15 plot smooth area distribu(on 10 Area curve 5 0 Connected linearly −5 0 0.2 0.4 0.6 0.8 1 x/L eminton Lord series Also used to find locaon of max wave drag contribu(on 21 Verificaon Tests Solid Sears-Haack Body • Known analy(cal wave drag Flow- soluon Through • Flow-through version created Sears−Haack r/L Sweep vs. Exact – Different radius, same area – Same analy(cal drag solu(on 1 • Conducted sweeps over r/L 0.8 and number of cung planes 0.6 D/q • Permimed verificaon of 0.4 proper applicaon of wave 0.2 drag theory OpenVSP Exact 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 r/L 22 Verificaon Tests • Convergence study on Sears-Hacck r/L = 0.04 vs. number of cung plane slices – <1% error aer 6 slices, <0.1% error aer 12 slices – Flow-through version within 0.016% error for equivalent r/L = 0.04 Convergence Study: Slices on Sears−Haack with r/L = 0.04 Convergence Study: Slices on Sears−Haack with r/L = 0.04 1 0.04 10 0.035 0 10 0.03 0.025 −1 10 0.02 D/q Error, % −2 10 0.015 0.01 −3 10 0.005 OpenVSP Exact −4 0 10 0 10 20 30 40 50 0 10 20 30 40 50 Number of Slices Number of Slices 23 Verificaon Tests Eminton Body • Known analy(cal wave drag solu(on • Similar area to a fuselage with swept wings • Conducted convergence study vs. number of cung plane slices – error <1% aer 34 slices Convergence Study: Slices on Eminton Body Convergence Study: Slices on Eminton Body 9 8 7 6 1 10 5 D/q 4 Error, % 3 2 0 10 1 OpenVSP Exact 0 0 10 20 30 40 50 0 10 20 30 40 50 24 Number of Slices Number of Slices Demo Accessing the Wave Drag Tool Accessible from the “Analysis” menu Plot area starts out empty un(l data exists 26 “Run” Tab • Select number of slices • Select number of rotaons • Choose XZ symmetry op(on – Will run same number of rotaons, but on 0-180° and update drag result accordingly • Select component set • Set Mach number and Sref • Choose output file (op(onal) 27 Running Tool • Fighter model example • Results appear upon clicking “START” bumon 28 Background Wave Drag Incorporang Implemen(ng Comparisons Demo Conclusion “Plot” Tab Manage from “Plot” tab Control which theta rotaon is visible All remaining visual tools Discrete data points in black, Fourier approximaon in blue 29 “Plot” Tab • Using global max drag bumon, reference bar and plane visualizer relocate accordingly 30 “Flow Faces” Tab • List auto-populates with exis(ng subsurfaces • Check the boxes next to subsurfaces intended to be flow faces • Tool will determine inlet/exit status 31 “Flow Faces” Tab • Fighter model example run with flow faces ac(vated 32 Body of Revolu(on Visualizing • Access drop-down menu from “Plot” tab • equivalent body of revolu(on using length, radius, and volume of exis(ng model Sears-Haack Body von Karman Ogive Lighthill’s Body 33 Mach Cung Plane Visualizer • A translucent plane on the main screen • Represents current theta and Mach angle • Locaon controlled by Slice Axis Reference slider • Turn on/off with visualizer toggle buon • Provides visual correlaon of model and area distribuon 34 Quesons? 35 .
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