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![Page 1: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/1.jpg)
School of Computing University of Leeds Computational PDEs Unit
A Grid-based approach to the validation and testing of lubrication models
Christopher GoodyerMartin BerzinsPeter JimackLaurence Scales (Shell Global Solutions)
Funded by DTI/EPSRC e-Science Core Programme (GR/S19486) and Shell Global Solutions
![Page 2: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/2.jpg)
School of Computing University of Leeds Computational PDEs Unit
A Grid-based approach to the validation and testing of lubrication models
Christopher GoodyerMartin BerzinsPeter JimackLaurence Scales (Shell Global Solutions)
Funded by DTI/EPSRC e-Science Core Programme (GR/S19486) and Shell Global Solutions
![Page 3: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/3.jpg)
Presentation Overview
• Background:– The White Rose Grid– Elastohydrodynamic lubrication (EHL)
• A Grid-enabled Problem Solving Environment (PSE):– Simulation– Grid Computing– Visualisation and Computational Steering within a PSE
• Hierarchical Parallelism– Implementation– Parallel simulation example
• Conclusions
![Page 4: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/4.jpg)
Background - The White Rose Grid
![Page 5: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/5.jpg)
Background – Elastohydrodynamic
Lubricaton (EHL)
• Applications:High pressure contacts such as gears, valve trains, etc.
•Environmental Issues:Energy efficiency frictionDurability wear
![Page 6: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/6.jpg)
Background - EHL (cont.)
Demanding mathematics and computer algorithms:
• Very High Loads + Small Areas
• High Pressures and Temperatures
• Deformation + Glass-like Lubricant
Lubricant Experiment Theory Prediction Computational Model
![Page 7: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/7.jpg)
Equations for the EHL Point Contact Problem
• System of equations in 2 space dimensions• Reynolds Equation – pressure distribution
• Film Thickness Equation – deformation
• Force Balance Equation – conservation law• Lubricant model – density, viscosity, temperature
0)()(
TH
XH
YP
YXP
X
22)'()'(
'')','(
00),(),(
yYxX
dydxyxPHYXgYXH
![Page 8: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/8.jpg)
Typical Point Contact Solutions
Film thickness
PressureTemperatur
e
![Page 9: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/9.jpg)
Grid-Enabled PSE - Overall Software Design
gViz
PSE (main)
Grid Visualise SteerPSE (collaborator)
gViz
Simulation
![Page 10: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/10.jpg)
Grid-Enabled PSE – Design (cont.)
gViz
PSE (main)
Grid Visualise SteerPSE (collaborator)
gViz
Simulation
![Page 11: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/11.jpg)
Grid-Enabled PSE - Simulation
• Wish to find set of lubricant model parameters (e.g. viscosity, pressure, temperature coefficients) which best match observed data
• Typically at least 10 such parameters to optimise
• Observations for different loadings (3), ambient temperatures (2) and slide:roll ratios (6)
• Nonlinear optimisation of
36
1
exp 2)(
jj
numjF FFR
![Page 12: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/12.jpg)
Grid-Enabled PSE – Simulation (cont)
• Each friction evaluation is an expensive EHL calculation• Currently use a NAG library simplex algorithm for the
multidimensional optimisation• Scope for parallelism and use of Grid:
– Could compute all 36 frictions in parallel at each R evaluation– More efficient to use continuation in the slide:roll parameters with
6 parallel processes– Each of these 6 processes may themselves be implemented in
parallel and launched on different Grid resources (each using multiple processors).
![Page 13: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/13.jpg)
Grid-Enabled PSE – Design (cont.)
gViz
PSE (main)
Grid Visualise SteerPSE (collaborator)
gViz
Simulation
![Page 14: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/14.jpg)
Grid-Enabled PSE – Grid Computing
• Based upon use of the Globus Toolkit:– Module provided to interrogate a GIIS server to analyse available
resources and their current status
– Job may be launched on selected resource(s) using Globus
– When job is spawned a connection is made back to the PSE (or Grid service) indicating which node of the Grid resource the simulation will be communicating from
• Although Grid certification is required to launch the simulation, use of gViz libraries allow collaborators around the world to see results of, or even steer, the simulation as it progresses
![Page 15: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/15.jpg)
Grid-Enabled PSE - Overall Software Design
gViz
PSE (main)
Grid Visualise SteerPSE (collaborator)
gViz
Simulation
![Page 16: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/16.jpg)
Grid-Enabled PSE – Design (cont.)
gViz
PSE (main)
Grid Visualise SteerPSE (collaborator)
gViz
Simulation
![Page 17: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/17.jpg)
Grid-Enabled PSE – Design (cont.)
gViz
Grid Visualise Steer
gViz
Simulation
PSE (main)
PSE (collaborator)
![Page 18: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/18.jpg)
Grid-Enabled PSE – The PSE
• The complete PSE package is called GOSPEL (Grid Optimisation Software for Problems of Elastohydrodynamic Lubrication)
• It is built using NAG’s IRIS Explorer software which uses a dataflow model
• The following IRIS Explorer map shows the three main modules:– GlobusSearch
– SteerGOSPEL
– VisualiseGOSPEL
![Page 19: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/19.jpg)
Example of a typical IRIS Explorer map for the PSE:
![Page 20: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/20.jpg)
Grid-Enabled PSE – Design (cont.)
gViz
PSE (main)
Grid Visualise SteerPSE (collaborator)
Simulation
gViz
![Page 21: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/21.jpg)
Hierarchical Parallelism
• Each friction calculation requires a costly EHL solve so this is implemented in parallel:– Parallel FAS multigrid
– Parallel multilevel multi-integration
• Each function evaluation requires 36 friction calculations so these are found in parallel– Use of continuation means that six sets of six is far more efficient
than 36 independent calculations.
![Page 22: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/22.jpg)
Hierarchical Parallelism (cont.)
![Page 23: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/23.jpg)
Hierarchical Parallelism (cont.)
• The following example shows typical speedups achieved…
• The loss of efficiency is due to early completion of some of the continuation runs:– Different processor speeds
– Different computational costs when different loads are applied
Np 1 6 12 24 48 96
Secs. 512.0 93.3 50.0 29.3 17.6 15.1
![Page 24: School of Computing University of Leeds Computational PDEs Unit A Grid-based approach to the validation and testing of lubrication models Christopher Goodyer.](https://reader035.fdocuments.in/reader035/viewer/2022070306/5515ed98550346dd6f8b527d/html5/thumbnails/24.jpg)
Conclusions
• Have demonstrated:– Solution of complex and computationally expensive EHL
problems within outer optimization wrapper– Hierarchical parallelism using Grid resources and software– Use of Globus toolkit with MPI, NAG and gViz libraries
• Have also:– Implemented within a PSE to allow interactive visualization and
computational steering (but not discussed here)
• Still to do:– Better load balancing– More versatile applications: e.g. actually designing lubricants!