CFD Simulation using LS-Dyna ICFD Method.pdf
- 1. Performing a CFDSimulation Using Ansa and LS-DYNA ICFD Erik Svenning, PhD DYNAmore Nordic erik.svenning@dynamore.se
- 2. Purpose ■ Introduction tothe ICFD solver in LS-DYNA ■ Setting up an ICFD simulation in Ansa ■ Final keyword setup using LS-PrePost ■ Summary ■ Set up an LS-DYNA ICFD simulation using Ansa and LS-PrePost Outline
- 3. Solver introduction ■ Featuresof the ICFD solver in LS-DYNA ■ An implicit solver for incompressible fluids ■ Recommended to use version R10.1 or R9.3 (or R11.0 released recently) ■ Uses the Finite Element Method (FEM) ■ 2D and 3D calculations ■ Automatic volume mesh generation ■ Well suited for coupled simulations ■ Fluid-Structure Interaction (FSI) ■ Conjugate heat transfer ■ CFD-DES coupling ■ Free surface flows (level set) ■ Non-Newtonian fluids ■ Turbulence models ■ Porous media ■ Steady state solver (from R10)
- 4. Typical workflow forsimulation setup ■ Ansa ■ Import and clean up geometry ■ Set PIDs for different BCs ■ Create surface mesh ■ Volume mesh created automatically by the ICFD solver ■ Export mesh ■ In standard LS-DYNA format up to Ansa version 18 ■ Minor modifications of mesh keywords manually or with script ■ Change *ELEMENT_SHELL to *MESH_SURFACE_ELEMENT. ■ Change *ELEMENT_BEAM to *MESH_SURFACE_ELEMENT. ■ Change *NODE to *MESH_SURFACE_NODE. ■ Change *PART to *ICFD_PART_TITLE. ■ Export in ICFD format from Ansa version 19 ■ Supported from version 19, but some unresolved issues in 19.0.0 ■ LS-PrePost ■ Final keyword setup
- 5. Activating ICFD supportin Ansa ■ Set DECK to LS-DYNA ■ The ICFD format is supported in Ansa from version 19 ■ Tools->Settings ■ Settings->Decks ■ Activate Enable LS-DYNA ICFD ■ Save settings ■ Restart Ansa ■ Remark for older versions of Ansa: ■ Create mesh in standard LS- DYNA format ■ Change the required keywords manually
- 6. Setting ICFD boundaryconditions ■ DECKS->BOUNDARY->ICFD_BOUNDARY ■ CONJ_HEAT ■ FREESLIP ■ FSI ■ NONSLIP ■ PRESCRIBED_VEL ■ PRESCRIBED_PRE ■ PRESCRIBED_TEMP ■ PRESCRIBED_TURBULENCE ■ Some are not yet available in 19.0.0 ■ FLUX_TEMP ■ FSWAVE ■ …
- 7. Setting ICFD initialconditions ■ DECKS->INITIAL->ICFD_INITIAL ■ New ■ Velocity ■ Temperature ■ Pressure ■ PID=0 sets initial conditions everywhere ■ TURBULENCE ■ For use in combination with RANS models ■ Initial turbulent intensity ■ Initial turbulent viscosity to laminar viscosity ratio
- 8. Defining ICFD points ■DECKS->AUXILIARIES->ICFD_DEFINE_POINT ■ Define ICFD points, e.g. to control the size of a refinement box
- 9. Converting to ICFDmesh ■ DECKS->AUXILIARIES->ICFD Convert ■ Convert between standard LS-DYNA mesh and ICFD mesh ■ Need to release the elements from the underlying geometry before conversion ■ In the Includes manager, check that the mesh is located under LSDYNA_CFD_MESH_MODULE
- 10. Example problem ■ Flowaround a cylinder ■ Channel dimensions ■ Length 0.2 m ■ Width 0.05 m ■ Height 0.08 m ■ Cylinder dimensions ■ Length 0.05 m ■ Diameter 0.01 m ■ Base located at ■ X = 0.05 ■ Y = 0.025 ■ Z = 0.0 ■ Fluid: water ■ Density 1000 kg/m^3 ■ Viscosity 1mPas ■ Boundary conditions ■ Re = 100 ■ Inlet: prescribed velocity of 0.01 m/s in x-direction ■ Outlet: zero pressure ■ Floor: no slip ■ Walls and roof: free slip
- 11. Simulation setup ■ Ansa ■Import or create and clean up geometry ■ Create surface mesh ■ Export in LS-DYNA ICFD format ■ LS-PrePost ■ Keyword setup ■ Post-processing
- 12. Geometry creation ■ Changeunits to m ■ Box ■ 0.2 x 0.05 x 0.08 m ■ Cylinder ■ Length 0.05 m ■ Diameter 0.01 m ■ Base located at (0.05; 0.025; 0.0) ■ PIDs ■ 1 Floor ■ 2 Cylinder ■ 3 Inlet ■ 4 Outlet ■ 5 Wall ■ 6 Roof ■ Important step: Open Properties. For all PIDs ■ Activate USER_SECID ■ SECID 1 ■ MID 1
- 13. Mesh generation ■ MESHmodule ■ Perimeters->Length ■ Box: 0.01 ■ Cylinder: 0.001 ■ Mesh Generation- >Free ■ Element type: tria Only tria supported ■ Elements->Release ■ Necessary for the ICFD export to work ■ Auxiliaries->ICFD Convert->Mesh to ICFD Mesh ■ Open Includes manager ■ Check that the mesh is located under the LSDYNA_CFD_MESH _MODULE ■ Export via File- >Export_LS-DYNA
- 14. Final setup withLS-PrePost ■ Include mesh file ■ Save as main.k ■ Close and open a new LS-PrePost window ■ Open main.k ■ ICFD_SECTION ■ ICFD_MAT ■ properties of water ■ DEFINE_CURVE ■ Constant 0.0 ■ Constant 1.0 ■ Boundary conditions ■ Inlet: ICFD_BOUNDARY_PRESCRIBED_VEL ■ Outlet: ICFD_BOUNDARY_PRESCRIBED_PRE ■ Floor and cylinder: ICFD_BOUNDARY_NONSLIP ■ Wall and roof: ICFD_BOUNDARY_FREESLIP ■ ICFD_CONTROL_TIME ■ TTM 1.0 ■ DT 0.01 ■ DATABASE_BINARY_D3PLOT ■ DT 0.1 ■ ICFD_PART_VOL ■ MESH_VOLUME
- 15. Post-processing with LS-PrePost ■Run the simulation ■ Open the d3plot file with LS-PrePost
- 16. Summary ■ In thiswebinar, we have set up an ICFD simulation using Ansa and LS-PrePost ■ Mesh generation with Ansa ■ Up to version 18: Change *NODE to *MESH_SURFACE_NODE, … ■ In SECTION_SHELL: Activate USER_SECID ■ Here, we created the surface mesh in Ansa and let the ICFD solver create the volume mesh automatically ■ This is the default approach, and necessary for problems with moving boundaries and remeshing ■ It is possible to employ a user defined volume mesh, but only tet elements are supported ■ Final keyword setup with LS-PrePost ■ Questions and comments ■ erik.svenning@dynamore.se
- 17. Thank you! Your LS-DYNAdistributor and more