1、2-1ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Chapter 21-way FSISolving FSI Applications using Workbench, ANSYS Mechanical and CFX1-way FSI2-2ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualOne-way Da
2、ta Transfer In Workbench both thermal and structural surface loads can be transferred from CFX to ANSYS Temperature Wall Heat Transfer Coefficient Pressure This includes both normal (Pressure) and tangential (Shear) loads In fact force data that comes directly from the solution of the momentum equat
3、ions is used CFD-Post performs the interpolation in the background A beta-feature also allows volumetric thermal loads to be transferred from CFX to ANSYS1-way FSI2-3ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualCHT MeshIntegrated Process in W
4、orkbenchCFD CHT SolutionGeometryThermal Loads Pressure Loads Thermal Stress SolutionExample Project Schematic1-way FSI2-4ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualConnecting Systems in Workbench Workbench supports two types of connections
5、Connections that share data Used when inputs and outputs of two connected cells are identical Can only be created between two cells of same type Connections that transfer data Used when output of one cell is input to a connected cell Usually created between two cells of different types Both connecti
6、on types are used for FSI systems in WorkbenchShared Data ConnectionTransfer Data Connection1-way FSI2-5ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualConnecting Analysis Systems for FSI Highlight desired ANSYS Analysis System in Toolbox and dr
7、ag on top of Solution cell (A5) in CFX Fluid Flow system Red outlines show cells that will Share and Transfer data with new system Connections are automatically created between both systemsDrag1-way FSI2-6ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Trainin
8、g ManualConnecting Analysis Systems for FSI Alternatively, right-click on Solution cell in Fluid Flow system, select Transfer Data To New, then select the appropriate target system Connections are automatically created between both systems1-way FSI2-7ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All righ
9、ts reserved. July 2009Inventory #002678Training Manual In the Customs Systems toolbox the FSI: Fluid Flow (CFX) Static Structural system can be added to the Project Schematic This transfers pressure loads from CFX to Mechanical Any project schematic can be saved/added to Custom Systems toolbox To ad
10、d a new workflow to Custom Systems, right-click on schematic white space and select Add to Custom from displayed pop-up menu Workbench will prompt for a custom template name to saveUsing Custom Systems=1-way FSI2-8ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #0026
11、78Training ManualGeometry and Mesh Considerations Fluid and Solid geometries should physically match Helpful for both geometries to come from a single CAD file DM can easily extract a fluid volume from a CAD model of the structure Mesh does not need to match 1-to-1 But similar mesh resolution will i
12、mprove interpolation accuracy Can write an ANSYS Input File and load into CFD-Post, along with the fluid mesh, to check interface mesh Must be a .inp file written from Workbench (not Mechanical APDL) CFD-Post recognizes .dat files as FLUENT files Check the Imported Load contour/vector plots in Mecha
13、nical These are automatically created after the import1-way FSI2-9ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualImported Loads In Mechanical an Imported Load entry will automatically be added to the tree when solution data is transferred from
14、CFX There are two Scoping Methods for imported loads Geometry Selection: Select faces on solid geometry to transfer CFD loads Named Selection: Select existing named selections to transfer CFD loads All boundary condition names in CFX results file will be exposed via drop-down1-way FSI2-10ANSYS, Inc.
15、 Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualData Transfer to Mechanical Systems CFX data is transferred to Mechanical Systems via CFD-Post Launched in background Only surface loads can be transferred automatically in Workbench Temperature transfer as a
16、 body load is a manual process (beta) CFD-Post performs interpolation process for vector and scalar quantities Mechanical nodal values are transferred by linear interpolation from the surrounding CFD surface nodes If interpolation process cannot find a face to map to, then closest point is chosen No
17、t conservative Interpolation process can be slow for large cases Planning to enhance interpolation process in a future release1-way FSI2-11ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training Manual Surface Temperature or Heat Transfer Coefficient (HTC) da
18、ta is transferred from CFX to Mechanical via a Thermal system Static Thermal, Transient Thermal, Thermal Electric supported for Mechanical analysis systems Solid temperature field will be solved in Mechanical May have already solved as Conjugate Heat Transfer (CHT) in CFD Engineering Data used to sp
19、ecify material properties for ANSYS Mechanical systems Need to make sure thermal properties are consistent with CFD Specific Heat, Thermal Conductivity, DensityThermal Transfer to Mechanical Systems1-way FSI2-12ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678T
20、raining Manual1. Right-click on Imported Load (Solution) object in Outline panel2. Select Insert Temperature or Insert Convection Coeff.3. Choose a scoping method and corresponding CFD surface4. For Convection Coeff., choose Near Wall Temperature or Ambient Temperature (see next slide)5. Highlight I
21、mported object to see contour and rangeThermal Transfer to Mechanical Systems1-way FSI2-13ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualThermal Transfer to Mechanical Systems If CHT has been solved in CFX, Temperature will be available on the
22、solid surface Preferable to transfer Temperature in this case If transferring HTC, check that calculated surface temperatures in Mechanical match those in CFX When importing HTC data (Convection Coeff. in Mechanical), can choose Near Wall Temperature or Ambient Temperature Method chosen should be co
23、nsistent with the way HTC was calculated in CFX Wall Heat Transfer Coefficient is the variable imported from CFX1-way FSI2-14ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualThermal Transfer to Mechanical Systems By default CFX will calculate Wal
24、l HTC using the Near Wall Temperature Temperature in the wall adjacent control volume See CFX doc for details HTC is often calculated using a specific reference temperature E.g the average fluid inlet temperature In these cases the parameter tbulk for htc is set in CFX Wall Heat Transfer Coefficient
25、 is then calculated using this reference temperature instead of the Near Wall Temperature Should then select Ambient Temperature in ANSYS and provide the same reference temperature1-way FSI2-15ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualPres
26、sure Transfer to Mechanical Systems Pressure data is transferred from CFX to Mechanical through a structural analysis system Static Structural, Transient Structural, Shape Optimization An Imported Pressure entry will appear by default To add additional CFX Pressure loads right-click on Imported Load
27、 (Solution) and select Insert Pressure1-way FSI2-16ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualThermal Stress WorkflowWorkflow 1: Thermal Data Only Transferred to MechanicalWorkflow 2: Thermal and Pressure Data Transferred to Mechanical(A5 t
28、o C5 link added manually)1-way FSI2-17ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualThermal Stress Workflow1. Solve CFD conjugate heat transfer (CHT) analysis for combined fluid and solid2. Transfer surface temperatures/HTC to a Thermal analys
29、is system Solve temperature field3. Connect to a Structural analysis system WB will apply 3D temperature field as a body load automatically Optionally apply Pressure load from CFD results Solve for deformations (stresses)1-way FSI2-18ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July
30、 2009Inventory #002678Training Manual Automotive Manifold Full conjugate heat transfer solution in FLUENT Cast iron solid material properties Free stream external convectionCFD Mesh ANSYS MeshThermal Stress Example1-way FSI2-19ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009In
31、ventory #002678Training ManualThermal and Structural LoadsSolid Temperature (CFD) Solid Temperature (ANSYS)Surface Pressure (CFD) Surface Pressure (ANSYS)1-way FSI2-20ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualANSYS Stress SolutionEquivalen
32、t Stress Total DeformationSolution Metrics: 5 minutes to process all loads and solve ANSYS stress problem1-way FSI2-21ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualAlternative Thermal Stress Workflow1. Solve CFD conjugate heattransfer (CHT) an
33、alysis forcombined fluid and solid2. Connect to a Structuralanalysis system Optionally apply Pressureload from CFD results3. Export a .cdb file from the Structural analysis4. Use CFD-Post to write 3D solid Temperature field onto the .cdb file (beta feature)5. Read .cdb file back into the Structural
34、analysis system and solve for deformations (stresses)1-way FSI2-22ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualAlternative Thermal Stress Workflow To export the .cdb file from Mechanical: Insert a Command Snippet similar to that shown and Sol
35、ve The example shown refers to a Named Selection of solid bodies called SolidPart This writes the .cdbfile without solvingthe model due to the/EOF command Use View Filesfrom the Projectpage to locate the.cdb file/PREP7CMSEL,S,SolidPartNSLE,S,1CDWRITE,DB,Export,cdbALLS/EOF1-way FSI2-23ANSYS, Inc. Pro
36、prietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualAlternative Thermal Stress Workflow In CFD-Post: First, set Edit Options as shown Restart CFD-PostNote: The Interpolation Tolerance controls the area or layer outside of the domain that is treated as part of the
37、domain for the purpose of interpolation. The default is 0.5%. Some nodes from the .cdb file will lie just outside of the CFX CHT domain, but as long as they lie within this layer data will be interpolated successfully. Spurious values in the exported load file (e.g. 1e38) may indicate that the Inter
38、polation Tolerance should be increased.1-way FSI2-24ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualAlternative Thermal Stress Workflow In CFD-Post: Load fluid results File ANSYS Import/Export Import ANSYS CDB Surface Select file exported from M
39、echanical Dont specify an associated boundary A User Surface object is created, but will not be visible Edit the User Surface and scope the Domains to only the solid domains Ensures that the fluid temperature is not used when interpolating Can visualize the User Surface by creating a Point Cloud, wi
40、th Sampling = Vertex and Reduction Factor = 11-way FSI2-25ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualAlternative Thermal Stress Workflow In CFD-Post: File ANSYS Import/Export Export ANSYS Load File Select the Unit System you are using in Me
41、chanical Export Temperature to a .sfe file and place in the directory where the .cdbfile came from Check the data in this file for expected units To read in the .sfe file in the Structural system use a Command Snippet See EX1 in the examples directory/PREP7/inp,export,sfe/SOLVE1-way FSI2-26ANSYS, In
42、c. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualTime-averaged Data Transfer Time-averaged data is useful in a number of cases, e.g. Averaged pressure loads from transient CFD simulations LES, DES, SAS Averaged HTC from transient CFD Turbine blade cooling
43、 No built-in support for time-averaged data transfer1-way FSI2-27ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualTime-averaged Data Transfer Thermal Variables transferred from CFX to ANSYS are Wall Heat Transfer Coefficient or Temperature To tra
44、nsfer a time-averaged quantity: Use Transient Statistics in CFX to generate the time-averaged quantity In CFD-Post use the Replace with Expression feature to overwrite Wall HTC or Temperature with the time-averaged value Original values are retained in the res file recover at any time Transfer data
45、as usual to ANSYS1-way FSI2-28ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualTime-averaged Data Transfer Structural Transferring structural (pressure) data can use the same approach, but requires some additional steps Boundary Flow data from th
46、e .res file will be used if available, so this must be explicitly turned off Enable the toggle Output Boundary Flows on the Results panel of the Solver Control form, and then setting the boundary flows to “None“ The CFX variable used is Absolute Pressure, minus the Reference Pressure So Absolute Pre
47、ssure.Trnavg should be generated Overwrite Absolute Pressure with the transient average Close the .res file, then re-open in CFD-Post and transfer data as usual You must close and re-open the res file in this case1-way FSI2-29ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inv
48、entory #002678Training ManualTransient Data Transfer Transient data can be transferred to steady state and transient Mechanical systems Source time can be selected from a drop-down list when Imported Load is highlighted in Outline panel By default, CFD-Post always loads last time step in sequence Lo
49、ad step “End Time” must match “Analysis Time” for Imported LoadSelect time from drop-down list1-way FSI2-30ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. July 2009Inventory #002678Training ManualTransient Data Transfer However, not practical for many transient cases Need to set up an Imported Load for each timestep Load mapping repeated n times slow Use 2-way framework for 1-way transients Automated tr
