Aeroelastic Gust Response

Transcription

1 Aeroelastic Gust Response Civil Transport Aircraft - xxx Presented By: Fausto Gill Di Vincenzo

2 What is Aeroelasticity? Aeroelasticity studies the effect of aerodynamic loads on flexible structures, taking into account the dependence of the aerodynamic loads on the deformation of the structure and vice-versa Standard Analysis available in MSC Nastran(Structure & Aero linear) Static Aeroelasticity(Sol144) longitudinal Trim Analysis Input Output Steady Aerodynamics Static Stability Derivatives Stiffness Properties Trim Analysis Inertia Properties Static Loads Static Deformations Flutter (Sol145) Stability Margin - Root Locus Input Output Oscillatory Aerodynamics Flutter Analysis Structural Stiffness Dynamic Stability Derivatives Inertia Properties Control System (Optional) 6/5/2012 2

3 What is Aeroelasticity? Aeroelasticity studies the effect of aerodynamic loads on flexible structures, taking into account the dependence of the aerodynamic loads on the deformation of the structure and vice-versa Standard analysis available in MSC Nastran(Structure& Aero linear) Dynamic Aeroelasticity(Sol146) Civil Transport Aircraft Gust Response Input Oscillatory Aerodynamics Structural Stiffness Inertia Properties Control System (optional) Output Frequency Response Transient Response Random Response Dynamic Loads Excitation Design Sensitivity and Optimization(Sol200) Input Static Aeroelasticand / or Flutter Input Design Model 1.Objective 2.Constraints 3.Design Variables Output Resized Structure Analysis Results Structural Modal tuning Mode Exp [Hz] Num [Hz] Error [%] First Second Third Fourth /5/2012 3

4 What is Aeroelasticity? Aeroelasticity studies the effect of aerodynamic loads on flexible structures, taking into account the dependence of the aerodynamic loads on the deformation of the structure and vice-versa Non Standard FSI analysis available in MSC Nastran OpenFSI(Structure & Aero linear or nonlinear) Transient Dynamic Aeroelasticity(Sol400) Transient Longitudinal Maneuver Input Output Unsteady Aerodynamics Transient Response Structural Stiffness Dynamic Loads Inertia Properties Control System (optional) Excitation Non linear Dynamic Aeroelasticity(Sol400) Input Output Unsteady Aerodynamics Transient Response Structural Stiffness Dynamic Loads Inertia Properties Control System (optional) Excitation HALE HA145 Acusolve.OpenFSI 6/5/2012 4

5 Topics Standard Aeroelastic Gust Response - Sol146 Civil Transport Aircraft - Gust Load Certification Deterministic approach - Discrete Gust Stochastic approach - Continuous Turbulence Static AeroelasticAnalysis with CFD data for Steady 1-g Load condition (UAV) -Sol144 Advanced Aeroelastic Gust Response - Sol400 UVLM.OpenFSI Unmanned Aerial Vehicle Structural Dynamic Optimization - Sol200 Discrete Gust Response at Trim Flight condition Aeroelastic Gust Response with Control System 6/5/2012 5

6 Aeroelastic Model Creation Civil Transport Aircraft- xxx Structural Stick Model Aerodynamic Model 6/5/2012 6

7 Aeroelastic Model Creation Structural-Aero Coupling Inboard Wing Coupling 6/5/2012 7

8 Aeroelastic Model Creation Structural-Aero Coupling Outboard Wing Coupling From Structural and Aerodynamic models 6/5/2012 8

9 Civil Transport Aircraft Certification Aeroelastic Model Aerodynamics given by DLM (Potential theory - Lifting surface) Mode # Hz Mode # Hz 6/5/2012 9

10 Civil Transport Aircraft Certification Structural-Aero Coupling Mode # Hz 6/5/

11 Civil Transport Aircraft Certification Structural-Aero Coupling Mode # Hz 6/5/

12 Solution - SPLINE Verification Structural-Aero Coupling Mode # Hz 6/5/

13 European Aviation Safety Agency (EASA) Certification Specification for Large Aeroplanes CS Gust and turbulence loads There are two methods widely accepted by the aeronautical authorities. Dynamic gust load conditions applied to aircraft consist of discrete gust and continuous turbulence(or continuous gust) Deterministic approach(discrete gust) The deterministicmethoddescribesthe worstcase atmosphericgustapproach. For discrete gust loads the atmospheric turbulence is assumed to have one-minus-cosine velocity profile that can be described as a function of time. Response and load time history correspond to solutions of the airplane equation of motion in time domain. Stocastical approach(continuous turbulence) For contuinuous gust loads, the atmospheric turbulence is assumed to have a Gaussian distribution of gust velocity intensities that can be specified in the frequency domain as a power spectral density(psd) function. For both methods a set of gust velocities for specific flight conditions has been defined. From several types of gust PSD functions the Von Kármán and Dryden function are widely used. 6/5/

14 Tasks of the Simulation Aeroelastic Model Creation Aerodynamic Model DLM Aero-Structure Coupling - Splining Check Compute the Gust Response Tuned Discrete Gust (TDS) - One-minus-cosine Gust model Results of interest Acceleration over the Wing Wing Root Bending Moment 6/5/

15 Civil Transport Aircraft Certification The Aircraft has to be able to withstand the Dynamic Gust Load Deterministic approach - Discrete Gust (Time domain) 6/5/

16 Deterministic approach - Discrete Gust Definition Uds U = π 2 [ 1 cos( s H )] Uds-Maximum Gust Velocity H -Gust Gradient Length L/2 -Half length of Gust s -Distance into the Gust Uds U = π 2 [ 1 cos( 2 s L) ] 6/5/

17 Deterministic approach - Discrete Gust Definition Uds U = π 2 [ 1 cos( 2 s L) ] H [ 30 ft 350 ft] = [360in 4200in] 2 H = L = in (Aircraft Length) Altitude - Sea level True Air Speed in/s MTOW = lb MFW = 51800lb OWE = 62500lb MLW = 84800lb Zmo = ft U ds = 29,75 ft / s = 356,75in / s 6/5/

18 Problem Data Flight Velocity in/s Speed of sound in/s (1126 ft/s) Mach Number 0.51 Air Density E-7 pound*s/in/in^3 Reference Chord 170 in Gust length in Gust Amplitude Uds in/s Simulation time 3 s x=0.08*v/fmax 11 in f 0.01 Hz 6/5/

19 Guideline Determine the frequency range to be considered. Determinethenumberofmodestobeused. Use enhanced modal reduction with a residual vector generated for the response degree of freedom. Determine the reduced frequencies at which aerodynamic matrices are to be computed. Take careoftherigid bodymotion 6/5/

20 Compute the Gust response Translational Displacement Side View Translational Displacement Front View 6/5/

21 Results - Tip Displacement Max Wing Tip Deflection Node 2064 Max 25.3 in (0.64 m) 6/5/

22 Results - Acceleration Nz@ Node 2001 Max g Min g 6/5/

23 Confidential Results - Acceleration Nz@ Node 2007 Max g Min g 6/5/

24 Confidential Results - Acceleration Nz@ Node 2025 Max g Min g 6/5/

25 Confidential Results - Acceleration Nz@ Node 2064 Max g Min g 6/5/

26 Results - Acceleration over the Wing Getting the Maximum of the Aeroelastic response over the wing Positive Normal Load Factor - Nz(Max) g g g g 6/5/

27 Results - Forces Bending Station#1 - Nz(Max) Max N-m Min N-m 6/5/2012

28 Civil Transport Aircraft Certification The Aircraft has to be able to withstand the Dynamic Gust Load Stochastic approach - Continuous Turbulence (Frequency domain) 6/5/

29 Tasks of the Simulation Compute the Gust Response Power Spectral Density (PSD) -Von Kármánfunction Results of interest PSD Acceleration of Wing Root PSD Bending Moment of Wing Root 6/5/

30 Continuous Turbulence Design Criteria Normalized gust intensity, Ā Characteristic frequency, N 0 RMS ofanyresponse variable, σ X 6/5/

31 Continuous Turbulence Design Criteria Limit Load Static Sol144 Incremental Dynamic Load Sol146 6/5/

32 Effect of L on Von Kármán PSD 6/5/

33 Continuous Turbulence Design Criteria PSD of Turbulence 6/5/

34 Problem Data Flight Velocity in/s Speed of sound in/s (1126 ft/s) Mach Number 0.51 Air Density E-7 pound*s/in/in^3 Reference Chord 170 in Scale of Turbulence in (2500) ft Frequency Range 0-60 Hz s x=0.08*v/fmax 11 in f 0.01 Hz 6/5/

35 Results - PSD Acceleration Nz@ Node 2001 F06 Output Extract RMS N 0 Incremental Load 6/5/

36 Results - PSD Acceleration Nz@ Node 2007 Normal Load Factor Incremental Load 6/5/

37 Results - PSD Acceleration Nz@ Node 2025 Normal Load Factor Incremental Load 6/5/

38 Results - PSD Acceleration Nz@ Node 2001 Normal Load Factor Incremental Load 6/5/

39 Results - Acceleration over the Wing Getting the Dynamic Load Increment over the wing Normal Load Factor -Nz(Max) g 1.69 g 1.31 g 1.52 g 6/5/

40 Results - PSD Vertical Bending Moment Bending Station#1 Static Load Incremental Dynamic Load 6/5/

41 Continuous Turbulence Design Criteria Incremental Dynamic Load got by Sol146 1-g Steady State by Sol144 Solution needs a high fidelity approach to get the 1-g steady state MSC Software has developed an advanced capability to use CFD aerodynamic pressure in Sol144 Hybrid Static Aeroelastic Solution with CFD data - Sol144 6/5/

42 Advanced Aeroelastic Solution - Sol400 OpenFSI Transient Longitudinal Maneuver Analysis without Control System - UAV Pilot input command - Control surface MSC Nastran UVLM.OpenFSI RESTART functionality Starting point for AeroServoElasticity(ASE).. Transient Longitudinal Trim Analysis with Control System - UAV Elevator Control system MD Nastran UVLM.OpenFSI RESTART functionality Comparison with standard solution Transient Gust Response Analysis with Control System - UAV Elevator Control system MD Nastran UVLM.OpenFSI RESTART functionality Comparison with standard solution Non Linear AeroelasticAnalysis -Non conventional Aircraft HALE MSC Nastran Large Displacement Capability IFASD Time Domain Linear and Nonlinear FSI Simulation of the AGARD Wing using MD Nastran s OpenFSI TM Unsteady Vortex lattice Method 6/5/

43 Aerodynamic Code - UVLM Geometric nonlinearity at subsonic flows Time domain aeroelastic simulation Free wake formation Liftduetovortexrollupathighangleofattack Aeroelastic response due to 1-D/2-D discrete gust and pilot input command CpdistributionfromTunneltestorCDF Stall modeling by strip method Airfoil definition NACA series or user defined Aerodynamic body modeling Aerodynamic blade component 6/5/

44 Transient Longitudinal Maneuver Analysis without C.S. α= 2.73 δ E = -2.5 Vertical displacement of the UAV center of mass δ E Overall vertical aerodynamic load vs UAV weight Maneuver path -Front view Maneuver path -Side view No Control System The UAV is not balanced Altitude lost about 1.34 m Structural and Aerodynamic solution stored RESTART Analysis 6/5/

45 Transient Longitudinal Maneuver Analysis Structural and Aerodynamic data recovered from the previous FSI simulation (δ E = -2.5 ) Aeroelastic response to a Pilot Input Command on the Elevator Vertical displacement of the UAV center of mass I II III Time history of the pilot input command - Elevator I III II I t = 5:6 s δ E = 2.3 Elev Pitch down Maneuver path -Side view II t = 6:7 s δ E = -2.8 III t = 7:7.4 s δ E = 1.72 Maneuver path -Front view Pitch up Pitch down It is possible to evaluate the aeroelastic response delay to a control surface input TRIM algorithm Control system Comparison with standard gust response Sol146 6/5/

46 Transient Longitudinal Maneuver Analysis without C.S. α= 2.73 δ E = -2.5 δ E Wake formation The free wake is part of the solution The aerodynamic mesh deforms with the structure Vortex Tip Rollup Free vortex wake propagation 6/5/

47 Transient Longitudinal Trim Analysis with Control System Aerodynamic load components - Reference cord system Load Balance z L FzWing Fx Fz a x Fz x α Wind FxWing W δ E TRIM algorithm developed in python Control System on the Elevator Translational Balance within X direction Translational Balance within Z direction Rotational Balance along Y axis Fz= 0 My = 0 Dynamic of Flight equations to be satisfied Fx= 0 6/5/

48 Transient Longitudinal Trim Analysis with Control System Aerodynamic overall Load - Fz Aerodyna amic Load [N] Weight Fz Time [s] Fz, Fx = 0 Translational balance is satisfied! 6/5/

49 Transient Longitudinal Trim Analysis with Control System CG -Rotation along y Rotation [Degree] Ry Time [s] My = 0 Rotational balance along y is satisfied My, Fz, Fx= 0 All Dynamic of Flight equations are satisfied Trim solution is got! Structural Trimmed condition AOA Elev It is now possible to perform Gust Analysis! 6/5/

50 Transient Gust Response Analysis with Control System EASA Certification Specification for light Aircraft: Ude-Maximum Gust Velocity H -Gust Gradient Length 25C/2 -Half length of Gust s -Distance into the Gust C -mean geometric chord Discrete GustProfile 1 -cos Ude=15,74 m/s T=0.393 s 6/5/

51 Transient Gust Response Analysis with Control System Structure Aerodynamics The Control system makes the UAV get back the trimmed flight condition! 6/5/

52 Transient Gust Response Analysis with C.S. Normal Load Factor Normal Load Factor Acceleration[g] Normal Load Factor Time[s] (Structure is linear) Sol146 and Sol400 are in good accordance It is possible to take into account for nonlinearities to study Aeroelastic response of structure with large displacement 6/5/

53 Transient Gust Response Analysis The UAV isabletorestorethe Trim flight conditionthankstothe ControlSystem Without Control With Control CG - Z Displacement Displacem ment[m] Time[s] Itcouldbe possibletoacton Airelonstoreducesloadon Wings Gust Alleviation 6/5/

54 Application - Nonlinear Aeroelastic Analysis MD Nastran Structural Model UVLM Aerodynamic Model Geometry Span of m Constant chord of 2.44 m 10 degrees dihedral angle at ends Two pods at 2/3 of from the mid-span Kg Central pod weighs 254 Kg. Overall weight of about Kg FEM Shells for the wing Solid for pods Aerodynamic 12 panels chordwise 30 panels spanwise Vortices shed from trailing edge and wing tip All six DOFs of the mid-span central section constrained to be zero. Gravity is not considered 6/5/

55 Application - Nonlinear Aeroelastic Analysis Flight condition M = 0.1 Sea Level Flight cruise velocity 12.5 m/s α = 16 Max vertical deflection of about 18 m No dynamic instability found Wake propagation - Ortho view Structural deformation -Front view 6/5/