Contribution to GMGW 1

Transcription

1 Contribution to GMGW 1 Rocco Nastasia, Saurabh Tendulkar, Mark Beall Simmetrix Inc., Clifton Park, NY Riccardo Balin, Scott Wurst, Ryan Skinner, Kenneth E. Jansen Department of Aerospace Engineering Sciences, University of Colorado at Boulder, Boulder, CO PID = 16 1 st Geometry and Mesh Generation Workshop Denver, CO June 3 4, 2017

2 Summary of grids generated Case HL CRM full gap Code(s) SimModeler (MeshSim/GeomSim) Starting Geometry Model Grid Type Number Grid Levels Parasolid unstructured tetrahedra 2 Utilized SimModeler from Simmetrix SimModeler is GUI built on top of MeshSim from Simmetrix CAD based, automatic mesh generation Mesh generation is fully automatic from a set of mesh attributes that describe the desired mesh Goal was to create meshes appropriate for PHASTA code from UC Boulder Specific goal was good starting mesh for adaptivity GMGW 1, Denver CO, June

3 Geometry Import and Preparation Chose Parasolid geometry since original geometry was created in NX (Parasolid is the modeling kernel in NX) Want to avoid translation to minimize geometry issues Initial geometry read into Parasolid without issues Some quick meshes showed no obvious problems with the geometry none were found later Modifications: Added air region unioned model with a box Removal of solid regions in the model Scribed edges on leading edges for convenience in applying mesh controls Minor topology clean up Geometry prep time: 1 2 hours Most of that figuring out what to do, not doing it GMGW 1, Denver CO, June

4 Geometry Import and Preparation Far field box geometry unioned with original Parasolid model Wireframe view of surrounding box to show scale of original model Solid regions in original model containing slats, airfoil, flaps, and body were made void Size of box based on committee meshes GMGW 1, Denver CO, June

5 Geometry Import and Preparation Scribe edges on all leading edge surfaces Scribe isoparametric edges along surfaces Automatically align scribed edges on adjacent surfaces Simplifies specification of mesh attributes in these areas GMGW 1, Denver CO, June

6 Geometry Import and Preparation Remove Redundant Topology (combined edges) Before: After: GMGW 1, Denver CO, June

7 Mesh Generation Process SimModeler process flow to set meshing attributes directly on model topology 1D graded mesh attribute applied to all airfoil leading edge 2D graded structured meshes attributes applied to leading edge and trailing edge surfaces GMGW 1, Denver CO, June

8 Mesh Generation Process 2D structured mesh on upper and lower slat surface Slat leading edge 1D graded mesh GMGW 1, Denver CO, June

9 Mesh Generation Process Preview Mode SimModeler has functionality for rapid preview of surface mesh attributes Only selected topology is meshed Multiple meshing case support Once meshing attributes are defined on a model, they can be copied and modified to quickly create different resolution meshes Many mesh attributes can be defined in terms of variables for additional flexibility GMGW 1, Denver CO, June

10 Surface Mesh Generation Extruded surface meshing along trailing edge surface Mesh gradation specified on the in plane edges of the face extrusions Specify the number of layers or size in the extruded direction Elements can be either triangles or quadrilaterals Curvature based refinement in high curvature areas Curvature refinement can be applied to any topological entity or the entire model domain Curvature refinement can isotropic or anisotropic (isotropic curvature refinement shown here) GMGW 1, Denver CO, June

11 Surface Mesh Generation Isotropic mesh refinement in areas of special interest Isotropic mesh refinement along edge at wing root Isotropic mesh face refinement at LE slat cove face GMGW 1, Denver CO, June

12 Volume Mesh Generation Volumetric Boundary Layer Mesh Generation Specify first layer thickness and gradation rate Boundary layer mesh allowed to grow until isotropic Colliding boundary layers are automatically resolved Unstructured Volumetric Mesh Generation Mesh refinement zones used to control mesh size in interior Anisotropic gradation from top of boundary layer where boundary layer was trimmed Mesh size gradation to far field mesh Mesh Improvement can target various mesh shape metrics GMGW 1, Denver CO, June

13 Boundary layer intersection resolution BL cannot grow to full height here Layers can be automatically pruned or shrunk Gap spacing is user controllable GMGW 1, Denver CO, June

14 Difficulties/Lessons Learned No real difficulties on this geometry We had never meshed this model before User who set up meshing attributes was not experienced SimModeler user Training was a 1 hour WebEx demonstrating how to use SimModeler Setting up all attributes for surface meshing required approx hours Approx. 50% 60% of this was iterations to tune mesh settings to match mesh to committee meshes Setting up attributes for volume meshing required approx. 3 hours Only 5 meshing attributes, but iterations are slower Minor additional changes made to attributes based on analysis runs. Final meshes used for analysis differ slightly from those initially submitted Estimate that repeating the entire process now would take 4 8 hours GMGW 1, Denver CO, June

15 Mesh Statistics Geometry Model Grid Type Grid Level Nodes BFaces Volume Cells HLCRM Full Gap Unstructured Tetrahedra Coarse 8.0 M 482 K 46.4 M Medium 22.4 M 1.27 M M Mesh generation run times (non interactive process) Surface meshing, volume meshing, mesh improvement Coarse mesh: 22 minutes Medium mesh: 90 minutes Coarse mesh was created by modifying mesh attributes on the surface to be a factor of 2 larger than medium mesh The 3D BL parameters are the same for the two grid levels First layer height = 1.0x10 3 Growth rate = 1.25 GMGW 1, Denver CO, June

16 Surface Mesh Wing Upper Surface GMGW 1, Denver CO, June

17 Surface Mesh Wing Lower Surface GMGW 1, Denver CO, June

18 Surface Mesh Wing Slat LE at Root GMGW 1, Denver CO, June

19 Surface Mesh Wing Flap TE at Root GMGW 1, Denver CO, June

20 Surface Mesh Wing Tip LE GMGW 1, Denver CO, June

21 Surface Mesh Wing Tip TE GMGW 1, Denver CO, June

22 Flap Gap Upper Surface GMGW 1, Denver CO, June

23 Volume Mesh Cut at y=277.5 GMGW 1, Denver CO, June

24 Volume Mesh Cut at y=638 GMGW 1, Denver CO, June

25 Volume Mesh Cut at y=1050 GMGW 1, Denver CO, June

26 Mesh Evaluation Meshes generated were run with the same solver, same initial conditions and same solver parameters as the committee full gap, unstructured all tet, Pointwise grids. Solution convergence, in terms of difference from fine grid result, was somewhat better for coarse grids at both AOA Solution convergence comparable for medium grids. Non linear convergence rate and solver iteration count was comparable (more detailed analysis ongoing). GMGW 1, Denver CO, June

27 Summary Were able to successfully generate meshes on this geometry Simulations were run with good results Adaptive simulation results in progress GMGW 1, Denver CO, June