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Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
Mesh Dependency - Monterrey institute
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Mesh Dependency - Monterrey institute

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Every time a CFD problem is solved, no influence from …

Every time a CFD problem is solved, no influence from
the mesh configuration is desired in the final results.
During our study, different ways of constructing meshes
for a heat transfer of a car interior were analyzed in an
attempt to find an optimal model that could allow an
acceptable precision when comparing the results with the
ones obtained from experimentation. Having the intention
of understanding the influence of the mesh over the
results, all possible ways of CFD meshes construction were
analyzed, as well as the variables that could be modified.

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  • 1. MESH DEPENDENCY Ivan Dario Arroyave ZuluagaAutomotive Engineering Research Center (CIMA)Tecnológico de Monterrey Campus Toluca México
  • 2. Opportunity Statement / Expected OutcomeCurrent StateIn a OEM, Cabin & Thermal models are meshed for analysis using tetrahedral meshwith generic requirements recommended by the Software Vendor. CFD engineershave encountered significant differences in the simulations when the grow rate andtype of element is changed.Desired StateFind the required mesh type and mesh requirements for each analysis creating Bestpractices.
  • 3. Robust Design• We are looking for a new general methodology to build grids for CFD problems; we would like to do our mesh design robust for different types of elements. Hence we selected robust design to carry out our analysis.• This is the first approach to mesh dependency problems; we want to understand not only how to optimize the mesh construction, but also figure out if Robust Design is a good tool to do this optimization.
  • 4. Background
  • 5. Background
  • 6. Background
  • 7. Background
  • 8. Opportunity Statement / Expected OutcomeDefroster Side Windows Defroster Windshield PhysicalPhysical test patterns test patterns
  • 9. Opportunity Statement / Expected OutcomeExpected Outcome (Specific physics test):• Understand sensitivity of meshing characteristics of the determined factors in the event of thermal analysisConstrains:• Software capability, computational cost
  • 10. Develop Concept: Current Best Practices
  • 11. Develop Concept The following parameters were considered critical for mesh construction using Hypermesh A. Tetra Number of uniform layers B. Tetra Growth rate C. Number of BL layers 4 1.6 1 1.1 D. First layer thickness F. BL Growth rate: 1mm 1.4 0.6mm 6 1 0 Noise/Tetra to Polyhedral • YES • NOC,D,F A B
  • 12. Parameter Diagram Control Factors: Tetra Number of uniform layers Tetra Growth rate Number of BL layers First layer thickness BL Growth rate SystemInput: Outputs:2D Mesh, Boundary Fluid Mesh process fit againstcondition physical test results multiple response Noise Factors: (R1,R2,R3) (e.g.) Tetra to polyhedral Noise Factor 1 Noise Factor 2 Symptoms: Noise Factor 3 Meshing time Solve time Quality Mesh
  • 13. Control Factor Strategy A - Tetra Number of uniform layers TNUL1 1 Layers• Tetra Number of uniform layers TNUL2 2 Layers TNUL3 3 Layers levels comprehend benchmark TNUL4 4 Layers observed typical values B -Tetra Growth rate TGR1 1.1 rate TGR2 1.2 rate• Tetra Growth rate levels is TGR3 TGR4 1.4 1.6 rate rate selected for its current best practices and the lower limit that C -Number of BL layers NBL1 0 Layers NBL2 2 Layers allows software. NBL3 4 Layers NBL4 6 Layers D– First layer thickness FLT1 0.6 mm• Number of BL layers , First layer FLT2 0.8 mm thickness And BL Growth rate is FLT3 0.9 mm FLT4 1 mm chosen to explore different ways to achieve fill out space without F - BL Growth rate BGR1 1. rate BGR2 1.2 rate interference between one surface BGR3 1.3 rate and its opposite. BGR4 1.4 rate
  • 14. Noise Factor StrategyFull factorial, two cases• First case one factor: – Tetra to Polyhedral (2 levels)• Second case Three Factors – Noise factor 1 (2 levels) – Noise factor 2 (3 levels) – Noise factor 3 (3 levels) Response StrategySeparated Analysis• R1. Numerical-fit physical results – % Defroster area 25 minutes. – % Defroster area 35 minutes.• R2. Qualitative-fit physical results• R3. Solving time
  • 15. Optimization Details response 1 Noise factor polyhedralDue to the parameters and parameters levels, an L16 orthogonal array waschose. The objective is to fit the response to experimental value, thenominal is best formulation is selected.
  • 16. Response Plots for Means
  • 17. Response Plots for S/N
  • 18. Results for one Response• Optimal levels and factors for Means – Factor A Level 3 – Factor B Level 4 – Factor C Level 1• Optimal level and factors for S/N – Factor A level 2 – Factor B level 2 – Factor C level 1
  • 19. Conclusions• Hypermesh is versatile enough to carry out an experimental mesh dependency for CFD Thermal Analysis.• This analysis should be carried out for each phenomena.• Variables (e.g. iteration convergence) from the specific solver should be considered as a response, in order to get general mesh construction rules.• This study is the first step to create rules for optimal mesh generation process.• Robust Design could be a useful tool to analysis Mesh Dependency when the quality of mesh does not interfere with the convergence speed.
  • 20. Thank you

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