Multi-Physics Simulation in Aerospace A Closer Look at Structural & Flow Induced Multi-Attribute Analysis

Transcription

1 Multi-Physics Simulation in Aerospace A Closer Look at Structural & Flow Induced Multi-Attribute Analysis Juan F. Betts, PhD, MBA Manager, Aeronautics, Space, & Defense Process Group Christophe Schram, PhD Aero-acoustics Project Leader, CAE Division

2 LMS, well positioned for accelerated growth 25 Years of Engineering Innovation The industry largest R&D commitment to Engineering Innovation Talented people, 700 professionals committed to customers success More than 3000 manufacturing companies actively use LMS products and services 100M Annual Revenue Strong financial track record of double digit profitable growth 2 copyright LMS International

3 A Global Company World-wide Sales & Customer Services Organization LMS HQ - Leuven - BELGIUM LMS NA - Detroit LMS UK LMS Deutschland LMS Russia LMS France - Paris LMS China - Beijing LMS Korea LMS NA - Los Angeles LMS NA - Washington D.C. LMS France - Lyon LMS Italia LMS China - Shanghai LMS Japan ALAVA-LMS Partnership LMS Singapore LMS regional offices : 17 LMS representatives offices copyright LMS International

4 Problem Definition A Coupled Aero-acoustics-structures: Wing Flap Design CFD Analysis Aero-acoustic Analysis Low radiated noise Kinematics Model (Multi-body Model) Flexible Body Model (Stress Model) Air Loads Durability Model (Fatigue Model) Kinematics Correlation (Loads, Deflections) Dynamics Correlation (Modes) Failure Criteria Correlation (Stress, Fatigue) Wind Tunnel Testing Aerodynamic Loads Dynamic Loads Wing deformation Low component stress High durability 4 copyright LMS International

5 Aero-acoustic Analysis CFD Analysis Aero-acoustic Analysis Low radiated noise Kinematics Model (Multi-body Model) Flexible Body Model (Stress Model) Air Loads Durability Model (Fatigue Model) Kinematics Correlation (Loads, Deflections) Dynamics Correlation (Modes) Failure Criteria Correlation (Stress, Fatigue) Wind Tunnel Testing Aerodynamic Loads Dynamic Loads Wing deformation Low component stress High durability 5 copyright LMS International

6 What is Aero-Acoustics (1)?? Flow-induced noise = sound or noise generated by flow-related phenomena Jets Vortex shedding (von Karman vortex street) Turbulent boundary layers and boundary layer separation Rotating surfaces in a fluid (propellers, fans) Flow-Induced Noise or Aero-Acoustics Definition = The study of the generation and transmission of sound by fluid flow For flow-induced noise propagation in water, e.g. cause by propellers for ships or submarines, the term hydro-acoustics is sometimes used Birth of aero-acoustics field => Prof. Sir James Lighthill 1952 : On Sound Generated Aerodynamically I, Proc. Royal Society of London, Series A : On Sound Generated Aerodynamically II, Proc. Royal Society of London, Series A222 6 copyright LMS International

7 What is Aero-Acoustics (2)?? Essential ingredients Flow : flow generates sound waves (pressure fluctuations) Source : flow noise is generated in a particular region, e.g. wake or boundary layer Acoustic medium (air, water) to transport or propagate the sound waves 7 copyright LMS International

8 Industrial relevance of Aero-Acoustics Numerical flow simulation [CFD Computational Fluid Dynamics] is a complex field Turbulent flows with high Reynolds-number Non-linear character : large sensitivity to small details Transient or non-stationary computations But large progress in commercial CFD codes Graphical software : GUIs for data input and results interpretation (flowlines, particle tracing) Mathematical algorithms : turbulence-models ; DES [Detached Eddy Simulation] ; LES [Large Eddy Simulation] Computer hardware : faster processors ; clusters or MPP [Massively Parallel Processing] ; GRID computing ; etc General industrial interest in aero-acoustics is of recent date : around 3-5 years 8 copyright LMS International

9 Direct Approach vs. Hybrid Approach Straightforward approach : Computational AeroAcoustics (CAA) At low - moderate Mach numbers: orders of magnitude of difference between Length scales: λ ac = L turb / M Magnitudes: only O(M 4 ) of the flow energy radiates into the far field High order schemes needed to capture acoustic propagation (numerical instabilities) Numerical cost of a direct CAA scales with Re 3 M -4 for a DNS [Direct Numerical Simulation] Re 2 M -4 for a LES [Large Eddy Simulation] Due to disparities between hydrodynamic and acoustic amplitudes on one side, and disparities between turbulent scales and acoustic wavelengths on the other side. Alternative : hybrid approach, based on Lighthill aero-acoustical analogy Separate generation and propagation of sound Flow field = generation of aero-acoustic sound sources due to flow effects Acoustics = propagation of sound waves caused by flow effects Cheaper and more flexible, low-order flow simulation tools are applicable, provided they do not damp high-frequency source components they retain radiation characteristics (dipole, quadrupole, ) 9 copyright LMS International

10 The hybrid approach in a nutshell Decoupling flow simulation from the acoustic simulation Flow computation : creating source field data Acoustic computation : post-processing of source field data Fundamental assumption = one-way coupling Unsteady flow produces sound and affects its propagation BUT: sound waves do not affect flow field significantly Principal application of the hybrid approach: flows at low Mach numbers Preferred simulation tools for the flow description Reynolds Averaged Navier-Stokes (RANS) solver time-averaged data Unsteady RANS unsteady, but only large scale Large Eddy Simulation (LES) Detached Eddy Simulation (DES) unsteady, broadband turbulence (up to grid & scheme cut-off frequency) Two important concepts: Acoustic far field: d >> λ Acoustic compactness: L << λ source region L λ d observer position 10 copyright LMS International

11 A crucial concept : sound vs. pseudo-sound Pressure fluctuations occur in any unsteady fluid flow Can be recorded by a microphone or sensed by our ear, Are often regarded as sound However, it is crucial to distinguish between the non-propagating (convective) component: pseudo-sound, and the propagating component: sound source region L λ d observer position Pseudo-sound Serves at balancing locally the momentum conservation equation Sound Is also called hydrodynamic pressure field, as it is not influenced by compressibility Propagates away from the turbulent region, at the speed of sound Results, in far field, from the constructive and destructive interferences between the local fluid motions At low Mach numbers, sound energy is a minute fraction of the turbulent energy: O(M 4 ) 11 copyright LMS International

12 Lighthill s Aero-Acoustical Analogy : concept Brilliant idea : distinction between source and wave propagation regions In all the fluid, and in particular in the turbulent region: fluid mechanics equations apply Wave propagation region: fluid mechanics equation reduce to a linear wave operator Matching of both theories? source region S y V observer position x propagation region uniform fluid at rest 12 copyright LMS International

13 Lighthill s Aero-Acoustical Analogy : formal statement Aeroacoustical analogy = reformulation of the equations of fluid dynamics inhomogeneous wave propagation equation. Flow field Conservation of mass Conservation of momentum Acoustic field ~ inhomogeneous wave propagation equation 13 copyright LMS International

14 Lighthill s Aero-Acoustical analogy : reference state Reformulation of fluid mechanics equations, and use of arbitrary speed c 0 : Definition of a reference state: Aero-Acoustical Analogy : with Lighthill s tensor Exact and perfectly useless! source region S y V observer position x propagation region uniform fluid at rest 14 copyright LMS International

15 Integral solution of Lighthill s analogy Solution using Green s fct sound scattering at boundaries obtained using acoustic solver (SYSNOISE) implicit integral solution equivalent aeroacoustical source, obtained through flow modeling Lighthill s tensor Purpose: simplify Lighthill s source term High Reynolds number Isentropic Low Mach number 15 copyright LMS International

16 Lighthill, Curle, Ffowcs Williams & Hawkings formulations In absence of solid surfaces, or using a tailored Green s function: Lighthill Quadrupole retarded time In presence of steady solid surfaces, and using free field Green s function: Curle Quadrupole, W M 8 Dipole, W M 6 In presence of moving surfaces: Ffowcs Williams & Hawkings Convected quadrupole Convected dipole Doppler factor copyright LMS International

17 LMS Implementation : SYSNOISE Aero-Acoustics CFD-Acoustics Coupling : Process Overview CFD Run 1) CFD computation in time domain (e.g. LES Large Eddy Simulation ; DES - Detached Eddy Simulation) 2) Export CFD data to external file LMS SYSNOISE Rev5.6 Data conversion : Time domain Frequency domain by Fourier transform [FFTW algorithm] SSN 5.6 Generate Aero-Acoustic Acoustic Sources SSN 5.6 Aero-acoustic results Acoustic Solution 17 copyright LMS International

18 LMS Implementation : SYSNOISE Aero-Acoustics Techniques for Numerical Vibro-Acoustics Finite Element Method [SYSNOISE FEM] Wave acoustics : numerical solution of wave equation (time domain) or Helmholtz equation (frequency domain) Volume discretization of acoustic domain (3D solid elements) Natural choice for interior acoustics Computationally intensive with respect to computer resources Boundary Element Method [SYSNOISE BEM] Wave acoustics : numerical solution of wave equation (time domain) or Helmholtz equation (frequency domain) Discretization of acoustic domain bounding surfaces only (2D surface elements) Natural choice for exterior acoustics (infinite domain!) Computationally very intensive with respect to computer resources 18 copyright LMS International

19 LMS Implementation : SYSNOISE Aero-Acoustics Techniques for Numerical Vibro-Acoustics Finite Elements Boundary Elements 3D volume meshing = higher 2D surface meshing = lower modeling modeling effort effort Modal approaches possible Heterogeneous fluid No modal approach Homogeneous fluid only Well-suited for interior acoustics Well-suited for exterior acoustics Symmetric matrices Well-known formalism Non-symmetric matrices for DBEM More difficult mathematics 19 copyright LMS International

20 Aero-acoustic Radiation Result 20 copyright LMS International

21 IV LMS Implementation : SYSNOISE Aero-Acoustics CFD-Acoustics Coupling : Source Generation Generation of Quadrupole Sources For handling flow-induced noise without presence of surfaces, e.g. turbulent jets Requires velocity data in the flow field volume stored as a function of time Generation of Dipole Sources For handling flow-induced noise in presence of static surfaces, e.g. turbulent boundary layers Requires pressure data on the walls stored as a function of time Generation of Fan Sources = Rotating Dipoles Sources For handling flow-induced noise caused by rotating surfaces, e.g. fan and blower blades Requires blade force data as a function of time stored Blade force data can be integrated along entire blade or over blade sections 21 copyright LMS International

22 LMS Implementation : SYSNOISE Aero-Acoustics SYSNOISE - Aerospace, Marine & Other Customer References Aerospace Corporation Boeing (various) Bombardier NASA Honeywell INTA Turbomeca Thales Qinetiq United Technologies 22 copyright LMS International Motorola Bose Thomson Philips Panasonic Zanussi Trane Embraco Bosch

23 SYSNOISE Aero-Acoustics Solution Pack Contents Acoustic Boundary Element Method & Acoustic Finite Element Method Automatic definition of Aero-Acoustic Sources from CFD data, based on Lighthill s Aero-Acoustic Analogy Sound radiation, sound propagation and sound scattering Plotting and 3-D imaging: SPL, Sound Power, ISO 3744, RMS, db weighting, (1/3)Octave, TL, 23 copyright LMS International

24 I Flow-Induced Noise : Terminology & Industrial Relevance Application 3 Aerospace Landing Gear Noise Aerospace Flaps noise Jet noise 24 copyright LMS International

25 Structural Models CFD Analysis Aero-acoustic Analysis Low radiated noise Kinematics Model (Multi-body Model) Flexible Body Model (Stress Model) Air Loads Durability Model (Fatigue Model) Kinematics Correlation (Loads, Deflections) Dynamics Correlation (Modes) Failure Criteria Correlation (Stress, Fatigue) Wind Tunnel Testing Aerodynamic Loads Dynamic Loads Wing deformation Low component stress High durability 25 copyright LMS International

26 Generalized Fluid-Structure Dynamic Interaction w r r r r r r ( r ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) k = M rk, rj F rk + pa rq M rk, rq dω rq + pl rq M rk, rq dω rq Ω r r Ω r r r r Point Forces Pressure Forces Fluid Loading w k 0 = M kjfj + pqmkqdω + w Ω Ω Ω 0 o G qo dω M kq dω w= structural velocity response M= structural mobility function P a = aero-acoustic loading P L = fluid loading w k = structural velocity response at location k M kq = structural mobility function (input at q and response at k) P q = aero-acoustic loading at location q 26 copyright LMS International

27 Fluid-Structure Dynamic Interaction Dissimilar Mesh Problem Fluid Mesh And Structural Mesh Dissimilar w k = Ω p q M kq dω 27 copyright LMS International

28 Time-Frequency Domain Conversion Relation between CFD time step t and dynamic analysis frequency f is given by where N is number of time steps for the CFD analysis k is an integer multiple for k = N/2, we reach the maximum frequency fs = 1/(2* t ), I.e. Nyquist frequency 28 copyright LMS International

29 Mechanical Design Slat system Concept Design: Adding Flexibility Rigid Beam Model Detailed FEM Add Flexibility to the system: System Deformation Component Deformation Component Stress System dynamics Following Parameterized Geometry 29 copyright LMS International

30 Wing flap application : Electro Hydrostatic Actuator EHA (Electro Hydrostatic Actuator) Displacement Rate Force/Torque Actuator LMS Virtual.Lab Motion Sensor 30 copyright LMS International

31 31 copyright LMS International

32 Internal Loads Model Air Loads CFD Analysis Aero-acoustic Analysis Low radiated noise Kinematics Model (Multi-body Model) Flexible Body Model (Stress Model) Air Loads Durability Model (Fatigue Model) Kinematics Correlation (Loads, Deflections) Dynamics Correlation (Modes) Failure Criteria Correlation (Stress, Fatigue) Wind Tunnel Testing Aerodynamic Loads Dynamic Loads Wing deformation Low component stress High durability 32 copyright LMS International

33 Structural Vehicle Level Analysis 1. Section FEM Creation 2.Additional Modeling Sizing Team 1 V5 Design Part V5 FEM V5 FEM 4. FEM Assembly via Node FEM Assembly Condensation or Connectors Connections 5. Apply sizing Team 2 Team 2 V5 Design Part NASTRAN File V5 FEM V5 FEM 3. Model Validation & Correction Integrator V5 Assembly FEM 7. Associative NASTRAN Driving 8. Post-Processing 6. Apply loading Loads mapping, table based loads Displacements, Envelop case to find critical loads Supplier NASTRAN File V5 FEM Release to stress groups 33 copyright LMS International

34 Mechanical Design Slat system Virtual.Lab Structures & Virtual.Lab Durability Durability Analysis of Safety Critical Components No cracks should occur in Lifetime (Safe Life without cracks) Extract loads from Virtual.Lab Motion System Level Durability analysis 34 copyright LMS International

35 Mechanical Design Slat system Component Optimization Optimize Component design: Analyze Component sensitivity for Design Parameter changes Optimize component stress/strain, durability for loads (minimize deformation, stress, weight, reach lifetime etc.) Optimize Manually and/or Automatically using parameterization 35 copyright LMS International

36 LMS Virtual.Lab Simulation fusion for performance engineering Upfront Engineering Detailed Engineering Refinement Engineering Design Pre-& Postprocessing Structural Analysis Vehicle Modeling System Performance Simulation Test Multi-CAD LMS Virtual.Lab Designer CATIA V5-embedded simulation CATIA CAE ABAQUS NASTRAN ANSYS LMS Virtual.Lab Stand-alone Integrated Simulation environment Engineering Collaboration Data Management Simulation Process Integration Design Optimization 36 copyright LMS International

37 LMS Virtual.Lab, the award-winning solution for Design-Right-First-Time performance simulation A unified framework for multidisciplinary virtual simulation System Level Simulation CAE/TEST Integration Hybrid Engineering Engineering-intuitive User Interface Powerful Graphics, Task/Process Automation Leveraging the Dassault Systèmes CAA V5 Structures Vibro-acoustics Motion Durability Hybrid Simulation Optimization 37 copyright LMS International

38 Mechanical Simulation Process System-level simulation of Landing Gear Geometry Kinematics Dynamic Simulation 38 copyright LMS International Loads Calculation Subassembly Loads Calculation Integrated ac Loads Calculation Component Durability Calculation

39 Example: Landing Loads & Landing Gear Retraction 39 copyright LMS International

40 Integrated CAE tools: LMS/Imagine free seminar Where? Hilton, Friday 17th 08:00 11:00 What? End-to-end simulation of aircraft mechatronic systems -> Landing gear example What? Structural analysis in V5 environment Verification of component design -> slat track example 40 copyright LMS International

41 Thank you Juan F. Betts, PhD, MBA Manager, Aeronautics, Space, & Defense Process Group Christophe Schram, PhD Aero-acoustics Project Leader, CAE Division