Real-Time Visualization of Aerospace Simulations Using

166 Pages·2002·3.16 MB·English

by  Anirudh Modi

ThePennsylvaniaStateUniversity
TheGraduateSchool
Departmentof ComputerScienceandEngineering
REAL-TIME VISUALIZATION OF AEROSPACE SIMULATIONS
USING COMPUTATIONAL STEERING AND BEOWULF CLUSTERS
AThesisin
ComputerScienceandEngineering
by
AnirudhModi
SubmittedinPartialFulfillment
oftheRequirements
fortheDegreeof
DoctorofPhilosophy
August2002
Weapprovethethesisof AnirudhModi.
DateofSignature
PaulE.Plassmann
AssociateProfessorofComputerScienceandEngineering
ThesisCo-Advisor
Co-ChairofCommittee
LyleN.Long
ProfessorofAerospaceEngineering
ProfessorofComputerScienceandEngineering
ThesisCo-Advisor
Co-ChairofCommittee
RajeevSharma
AssociateProfessorofComputerScienceandEngineering
PadmaRaghavan
AssociateProfessorofComputerScienceandEngineering
MarkD.Maughmer
ProfessorofAerospaceEngineering
RajAcharya
ProfessorofComputerScienceandEngineering
HeadoftheDepartmentof ComputerScienceandEngineering
iii
ABSTRACT
In this thesis, a new, general-purpose software system for computational steering has
been developed to carry out simulations on parallel computers and visualize them remotely in
real-time. The steering system is extremely lightweight, portable, robust and easy to use. As
a demonstration of the capabilities of this system, two applications have been developed. A
parallel wake-vortex simulation code has been written and integrated with a Virtual Reality
(VR) system via a separate graphics client. The coupling of computational steering of paral-
lel wake-vortex simulation with VR setup provides us with near real-time visualization of the
wake-vortex data in stereoscopic mode. It opens a new way for the future Air-Traffic Control
systems to help reduce the capacity constraint and safety problems resulting from the wake-
vortex hazard that are plaguing the airports today. In another application, an existing compu-
tational fluid dynamics code has been integrated with the steering system to enable interactive
visualizationofcomplexflowsimulationsfromanyremoteworkstation. Benefitsofscalability
anddimensionalreductionarisingfromthisapproachhavebeenimperativeinthedevelopment
of this system. This system makes the visualization of flow simulations easier, efficient, and
most-importantlywithoutanydelayasandwhentheresultsaregenerated,thusgivingtheuser
much greater flexibility in interacting with the huge amounts of data. At a more basic level,
the ability to get “immersed” in the complex solution as it unfolds using the depth cue of the
stereoscopic display and the near real-time nature of the computational steering system opens
awholenewdimensiontothescientistsforinteractingwiththeirsimulations.
iv
TABLE OF CONTENTS
LISTOFFIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
LISTOFTABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
Chapter1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Real-TimeSimulationsandVirtualEnvironments . . . . . . . . . . . . . . . . 1
1.2 RepresentativeApplications . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 Real-TimeSimulationofWake-VortexHazards . . . . . . . . . . . . . 5
1.2.2 ComputationalFluidDynamicsVisualization . . . . . . . . . . . . . . 9
1.3 ThesisFlow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Chapter2. IntegratedVirtualEnvironments . . . . . . . . . . . . . . . . . . . . . 11
2.1 VirtualReality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.2 ClassificationofVRSystems . . . . . . . . . . . . . . . . . . . . . . 12
2.2 VRHardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.1 InputandTrackingDevices . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.2 CAVE/RAVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3 VRSoftware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3.1 CAVELib . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3.2 OpenGL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
v
2.3.3 OtherHigh-levelSoftwareforVRApplications . . . . . . . . . . . . . 23
2.4 IVESystemsforAir-TrafficControl(ATC) . . . . . . . . . . . . . . . . . . . 25
Chapter3. ParallelComputingandBeowulfClusters . . . . . . . . . . . . . . . . 29
3.1 TaxonomyofParallelComputerArchitectures . . . . . . . . . . . . . . . . . . 29
3.2 ParallelizationStrategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.3 BeowulfClusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.4 MessagePassingInterface . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Chapter4. ComputationalSteering . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1 PortableObject-orientedScientificSteeringEnvironment(POSSE) . . . . . . . 44
4.2 Real-TimeImplementationIssues . . . . . . . . . . . . . . . . . . . . . . . . 49
4.2.1 Endianness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.2.2 Byte-alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.2.3 Datacoherence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.3 OverheadandScalability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.4 ExperimentalResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.4.1 SingleClientPerformance . . . . . . . . . . . . . . . . . . . . . . . . 62
4.4.2 MultipleClientPerformance . . . . . . . . . . . . . . . . . . . . . . . 63
4.4.3 SymmetricMulti-Processor(SMP)vs. Uni-ProcessorServer . . . . . . 64
Chapter5. Wake-VortexSimulations . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.1 Wake-VortexTheory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.2 SimulationComplexity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.3 Pseudocode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.4 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
vi
Chapter6. ComputationalFluidDynamicsSimulations . . . . . . . . . . . . . . . 84
6.1 ParallelUnstructuredMaritimeAerodynamics(PUMA) . . . . . . . . . . . . . 84
6.1.1 FiniteVolumeFormulation . . . . . . . . . . . . . . . . . . . . . . . . 85
6.1.2 DomainDecomposition . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.1.3 ParallelizationinPUMA . . . . . . . . . . . . . . . . . . . . . . . . . 89
6.1.4 BoundaryConditionImplementation . . . . . . . . . . . . . . . . . . 90
6.2 Real-TimeVisualization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.2.1 ModificationstoPUMA . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.2.2 GraphicalUserInterface . . . . . . . . . . . . . . . . . . . . . . . . . 92
6.2.3 ScalabilityandDimensionalReduction . . . . . . . . . . . . . . . . . 100
Chapter7. ConclusionsandFutureWork . . . . . . . . . . . . . . . . . . . . . . 106
7.1 FutureWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
AppendixA. C++SourceforWake-VortexProgram . . . . . . . . . . . . . . . . . 121
A.1 SampleServerInputFile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
A.1.1 vortex.inp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
A.1.2 trajectory1.inp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
A.2 SampleAirportInputFile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
A.2.1 San-FranciscoAirport(SFO.inp) . . . . . . . . . . . . . . . . . . . . . 121
A.3 SimulationCode(Server-side) . . . . . . . . . . . . . . . . . . . . . . . . . . 123
A.4 Headerfileforwake-vortexlibrary(vortex.h) . . . . . . . . . . . . . . . . . . 129
A.5 Headerfileforwake-vortexlibrary(wing.h) . . . . . . . . . . . . . . . . . . . 132
vii
AppendixB. C++SourcefortheCFDClientApplication . . . . . . . . . . . . . . 136
B.1 SampleinputfileforPUMA . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
B.2 AdditionstoPUMA(Server-side) . . . . . . . . . . . . . . . . . . . . . . . . 136
B.3 GraphicalUserInterface(Client-side) . . . . . . . . . . . . . . . . . . . . . . 139
AppendixC. C++SourceforPOSSETestPrograms . . . . . . . . . . . . . . . . . 144
C.1 SingleClientPerformanceTest . . . . . . . . . . . . . . . . . . . . . . . . . . 144
C.1.1 Server-sideprogram . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
C.1.2 Client-sideprogram . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
C.2 MultipleClientPerformanceTest . . . . . . . . . . . . . . . . . . . . . . . . . 147
C.2.1 Server-sideprogram . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
C.2.2 Client-sideprogram . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
C.3 SMPvs. UPPerformanceTest . . . . . . . . . . . . . . . . . . . . . . . . . . 149
C.3.1 Server-sideprogram . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
C.3.2 Client-sidescript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
viii
LIST OF FIGURES
1.1 B-727vortexstudyphoto(Courtesy: NASADrydenFlightResearchCenter) . 6
1.2 AVOSSsubsystemarchitecture[29] . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 CAVEdiagram(CourtesyEVL[49]) . . . . . . . . . . . . . . . . . . . . . . . 18
2.2 ScreenshotofaCAVEapplication(Courtesy: SARA,Netherlands) . . . . . . . 19
2.3 SnapshotoftheIHPCARAVE . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4 CrystalEyesShutterGlassesandtheWand(CourtesyFlurchick[50]) . . . . . 20
2.5 AsimpleCAVELibprogramwritteninC . . . . . . . . . . . . . . . . . . . . 22
2.6 AnIVEsystemforATC:NASAFutureFlightCentral’stower[64] . . . . . . . 28
3.1 Flynn’sClassification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.2 ClassificationofParallelComputers . . . . . . . . . . . . . . . . . . . . . . . 32
3.3 SchematicofatypicalBeowulfcluster . . . . . . . . . . . . . . . . . . . . . . 35
3.4 COsteffectiveCOmputingArray-2(COCOA-2) . . . . . . . . . . . . . . . . . 36
3.5 Asimple“HelloWorld”MPIprogramwritteninC++ . . . . . . . . . . . . . . 40
3.6 OutputproducedbyMPIprograminFig. 3.5whenrunon 8processors . . . . 41
3.7 MPI code written in C++ depicting communication of custom structure con-
tainingdynamicallyallocatedmembers . . . . . . . . . . . . . . . . . . . . . 42
4.1 InheritancediagramforPOSSEclasses . . . . . . . . . . . . . . . . . . . . . 46
4.2 UMLDiagramforPOSSEclasses . . . . . . . . . . . . . . . . . . . . . . . . 47
4.3 AschematicviewofPOSSE . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.4 Asimple,completePOSSEserverapplicationwritteninC++ . . . . . . . . . . 50
ix
4.5 Asimple,completePOSSEclientapplicationwritteninC++ . . . . . . . . . . 51
4.6 AsimpleC++functiontodeterminetheendiannessofanysystem . . . . . . . 55
4.7 AsimpleC++functiontoreversebyte-orderingofanydatatype . . . . . . . . 55
4.8 PackingandunpackingofacustomC++structure . . . . . . . . . . . . . . . . 59
4.9 EffectiveNetworkBandwidthvs. Sizeofdatarequestedbyclient . . . . . . . 65
4.10 EffectiveNetworkBandwidthvs. Numberofsimultaneousclients . . . . . . . 65
4.11 EffectofSMPvsUPmachineontheserver . . . . . . . . . . . . . . . . . . . 66
5.1 Schematicofawake-vortexpair . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.2 Nomenclature used for the velocity induced by a 3D, straight vortex segment
(CourtesyKatzandPlotkin[81]) . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.3 AlgorithmforWake-Vortexprediction . . . . . . . . . . . . . . . . . . . . . . 73
5.4 Wake-VortexSimulationSystem . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.5 UMLDiagramforWake-vortexclasses . . . . . . . . . . . . . . . . . . . . . 75
5.6 SounddBlevelasafunctionofanglefromthejetaxis[90] . . . . . . . . . . . 80
5.7 SounddBlevelasafunctionofdistancefromthejetnozzle . . . . . . . . . . . 80
5.8 Bergenclientcodeforsimulatingnoiselevel . . . . . . . . . . . . . . . . . . . 81
5.9 Screenshot of the Wake-Vortex simulation for a single aircraft from a visual-
izationclient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.10 Screenshot of the Wake-Vortex simulation for several aircraft flying above the
SanFrancisco(SFO)airport . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.11 Screenshot of the Wake-Vortex simulation for several aircraft flying above the
NewYork–JohnF.Kennedy(JFK)airport . . . . . . . . . . . . . . . . . . . . 83
x
6.1 Section depicting unstructured grid for aircraft landing gear geometry (Cour-
tesySouliez[95]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
6.2 16-waypartitioningofthelandinggeargrid(figure6.1)fromtheGibbs-Poole-
Stockmeyerreordering(CourtesySouliez[95]) . . . . . . . . . . . . . . . . . 88
6.3 Different cases when iso-surface cuts the face of the tetrahedron (Courtesy
Bourke[100]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
6.4 APOSSEGUItoconnecttotheflowsolver . . . . . . . . . . . . . . . . . . . 94
6.5 A POSSE client application depicting iso-surfaces for a flow solution over the
Apachehelicopter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
6.6 AsimpleFLTKapplicationwritteninC++ . . . . . . . . . . . . . . . . . . . . 96
6.7 AsimpleVTKapplicationwritteninC++ . . . . . . . . . . . . . . . . . . . . 97
6.8 OutputfromtheFLTKapplicationshowninFig. 6.6 . . . . . . . . . . . . . . 98
6.9 OutputfromtheVTKapplicationshowninFig. 6.7 . . . . . . . . . . . . . . . 98
6.10 UMLDiagramforclientGUIclasses . . . . . . . . . . . . . . . . . . . . . . . 99
6.11 ScreenshotofPUMAGUIwithTecplotfilter . . . . . . . . . . . . . . . . . . 101
6.12 RelativesizeofX-coordinateiso-surfacesfortheApachecase . . . . . . . . . 103
6.13 RelativesizeofMachnumberiso-surfacesfortheApachecase . . . . . . . . . 104
6.14 RelativesizeofC iso-surfacesfortheApachecase . . . . . . . . . . . . . . . 104
p
6.15 Gridsensitivityanalysisforiso-surfaces . . . . . . . . . . . . . . . . . . . . . 105