1、Latest developments in solving large simulation models in view of pass-by noiseAIA-DAGA March 20th 2013,Merano2Latest developments in solving large simulation models in view of pass by noise-OverviewReview of applicable simulation techniquesPerformance comparison for computing full vehicle PBN targe
2、t FRFs up to 4 kHzTPA based in-room pass-by noise model123Conclusion43Pass-by noise engineering In-RoomTime domain source contribution analysis=yk=NTFkiujQiHji024681012141618x 104-0.4-0.3-0.2-0.100.10.20.3024681012141618x 104-0.4-0.3-0.2-0.100.10.20.30.4LW12krdx=0 x=-=targets(measured&predicted)=ind
3、icators(measured)=sources(identified)4Energetic TPA for PBN Engineering024681012141618x 104-0.8-0.6-0.4-0.200.20.40.60.8024681012141618x 104-0.4-0.3-0.2-0.100.10.20.3u1(t)yk(t)+ykn(t)024681012141618x 104-0.8-0.6-0.4-0.200.20.40.60.8024681012141618x 104-0.8-0.6-0.4-0.200.20.40.60.8024681012141618x 10
4、4-0.4-0.3-0.2-0.100.10.20.3024681012141618x 104-0.2-0.15-0.1-0.0500.050.10.150.2Qn(t)Q1(t)yk1(t)FIR HjiLoads(synthesized)Indicators(measured)Contributions(synthesized)Targets(synthesized)123FIR characteristics calculated from Frequency domain TPA024681012141618x 104-0.4-0.3-0.2-0.100.10.20.3un(t)FIR
5、 FIR NTFkiFIR FIR characteristics derived frommeasured NTFs11.75-5.00mVehicle Position70.0020.0030405060253545556523283338434853586368dB(A)Pa5.14Curve5.14m68.23dB(A)68.21dB(A)64.15dB(A)56.00dB(A)56.59dB(A)54.55dB(A)60.85dB(A)54.62dB(A)61.13dB(A)FRight SideFRight Side-TotalFRight Side-PowertrainFRigh
6、t Side-ExhaustFRight Side-TailpipeFRight Side-Tire_FLFRight Side-Tire_FRFRight Side-Tire_RLFRight Side-Tire_RRTotal PBN and contributions Efficient Acoustic Source Quantification Limited amount of sensor required Bandwidth:From 150 Hz to 8 kHz5Latest developments in solving large simulation models i
7、n view of pass by noise-OverviewReview of applicable simulation techniquesPerformance comparison for computing full vehicle PBN target FRFs up to 4 kHzTPA based in-room pass-by noise model123Conclusion4Conventional(I)BEM:limited to medium sized models(25 knodes).Because BEM matrices are fully popula
8、tedMemory requirements O(n2)Direct Solving Factorization O(n3)Fast Multipole BEM:Fast Multipole ExpansionOctree Structure:BEM nodes are divided into cells at different levels.This happens at each frequency.For cells far away from each other(see x nodes and y nodes of 2 cells in picture),Greens kerne
9、l function is replaced with:Suppose we have 10 x nodes and 10 y nodes.21 operations to get the influences conventional BEM would need 100 operations O(n(log(n)2)Fast Multipole BEMRay AcousticsSound travels as rays:this assumption becomes more valid with increasing frequencyHowever difficult to captu
10、re accurately:Multiple diffraction:a ray hitting an edge should split into a new bundle of rays,each of which can diffract again on other edgesMultiple reflections:in highly reverberant spaces,smaller(energy)errors might build up after many reflections a good candidate for tyre and exhaust sources b
11、ut not ideal for engine sources.88 copyright LMS International 2010Field Response for Warning Sound in front of bumper(Front Right)Comparison between FMBEM and Ray Acoustics Multiple Cars650 HzRay Acoustics TessellatedRay Acoustics BEM MeshFast Multipole BEM(reference)2500 Hz9Field Response for Warn
12、ing Sound in front of bumperComparison between FMBEM and Ray AcousticsFEM PML/AMLFinite layer of FEM elements forms a Perfectly Matched Layer which absorbs waves traveling outwards.The absorption is obtained by a transformationThis ensures no waves travel back into the FEM domain after reflection(to
13、 satisfy Sommerfeld)accurate solution obtained on solution anywhere else is obtained using a Kirchhoff surface integral,similar to the post-processing step in BEMA locally conform implementation allows using any convex shape EFFECT ON PERFORMANCE!LMS Virtual.Lab offers AML(automatically Matched Laye
14、r),in which the PML layer is automatically built on solver levelDirect MUMPS solver and iterative Krylov solver supportedin11FEM Adaptive Order(FEM AO)Available in LMS Virtual.Lab 12(Summer 2013)FEM AO,the next generation FEM Acoustic solver:Higher order shape functions are used to represent the pre
15、ssure inside each elementAt order 10,an element can span more than 2 acoustic wavelengths.The solver automatically increases element order and therefore nr of DOFs in the model with frequency fixed nr of DOFs for conventional FEM solvers.Important savings on time and memory in lower frequenciesThis
16、allows for smaller model definition on pre-processor(LMS Virtual.Lab)which can be handled easierDiscretization only needs refinement in order to capture accurately the geometry and(vibration)boundary conditions12Latest developments in solving large simulation models in view of pass by noise-Overview
17、Review of applicable simulation techniquesPerformance comparison for computing full vehicle PBN target FRFs up to 4 kHzTPA based in-room pass-by noise model123Conclusion413Simulation model descriptionSeveral FEM models and a BEM model were built for a full vehicle(Chrysler Neon)including the surface
18、 of the powertrain to compute the target FRFs for a TPA PBN modelA reciproque approach is used with 19 monopole sources both left and right from the vehicle located 7.5 m from the center line and from-6 m till 12 m from the back of the vehicle,all at 1,2 m above the ground.There were 2 receivers per
19、 tyre,6 for the engine,and 2 for the exhaust(muffler and tailpipe)14Comparison for Neon PassBy Noise Model up to 4 kHz3 frequency ranges were defined to allow for 3 model sizes for conventional FEM and to adjust solver parallelization settings per range to optimally use the hardware.FEM AO updates t
20、he model size automaticallyFEM AO was about 2 times faster but needed more memory compared to the FEM models for 2 kHz.Many elements in FEM AO had lower order for 2 kHz.AML requires additional DOFs for the FEM AO at low frequencies.The higher you go in frequency,the better the results get for both s
21、peed and memory for FEM AOFor the mid frequency range,FEM AML iterative solver needed 2h/freq and FMBEM 1h/freq.This is both remarkably slower than the FEM AO models with direct MUMPS solver15FEM AO:evolution of model constitution,size and performance for the highest frequency rangeEvolution of mode
22、l constitution.With higher frequencies more element of higher order are usedEvolution of total#DOF,memory and solving time which are all frequency dependent for FEM AO16Accuracy Comparison for Neon Pass By Noise Model up to 4 kHz17PBN contribution results New ISO 362 Acceleration gear 312.00-5.00mVe
23、hicle Position70.0030.0040506032343638424446485254565862646668dB(A)PaFLeft Side-PowertrainFLeft Side-ExhaustFLeft Side-TailpipeFLeft Side-Tire_FLFLeft Side-Tire_FRFLeft Side-Tire_RLFLeft Side-Tire_RRFLeft Side-Total12.00-5.00mVehicle Position70.0030.0040506032343638424446485254565862646668dB(A)PaFRi
24、ght Side-PowertrainFRight Side-ExhaustFRight Side-TailpipeFRight Side-Tire_FLFRight Side-Tire_FRFRight Side-Tire_RLFRight Side-Tire_RRFRight Side-TotalA set of simulation FRFs was used to propagate previously identified sources of a real vehicleTypical trends can be observed:tailpipe contribution gr
25、ows as the vehicle passes by,left tyres contribute more to left microphones compared to right tyres and vice versa,front tyres contributions peak earlier compared to rear tyres18Latest developments in solving large simulation models in view of pass by noise-OverviewReview of applicable simulation te
26、chniquesPerformance comparison for computing full vehicle PBN target FRFs up to 4 kHzTPA based in-room pass-by noise model123Conclusion419ConclusionThis paper aimed at providing an overview of simulation methods to predict exterior acoustic FRFs for a full vehicle in view of using these FRFs in a pa
27、ss by noise TPA model.The challenge in this application is model size and therefore computational performance in terms of memory and time is key.FMBEM,Ray Acoustics and FEM AML techniques are explained as well as a new promising implementation of adaptive order FEM,called FEM AO in LMS Virtual.Lab A
28、coustics.The latter proved to be the most promising for a frequency range up to 4 kHz.20Latest developments in solving large simulation models in view of pass by noise-OverviewReview of applicable simulation techniquesPerformance comparison for computing full vehicle PBN target FRFs up to 4 kHzTPA based in-room pass-by noise model123Conclusion4
