workbench cfx单向流固耦合简介及实例

2-1 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Chapter 2 1-way FSI Solving FSI Applications using Workbench, ANSYS Mechanical and CFX 1-way FSI 2-2 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualOne-way Data 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 equations is used • CFD-Post performs the interpolation in the background • A beta-feature also allows volumetric thermal loads to be transferred from CFX to ANSYS 1-way FSI 2-3 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training Manual CHT Mesh Integrated Process in Workbench CFD CHT SolutionGeometry Thermal Loads Pressure Loads Thermal Stress Solution Example Project Schematic 1-way FSI 2-4 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualConnecting Systems in Workbench • Workbench supports two types of connections – 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 connection types are used for FSI systems in Workbench Shared Data Connection Transfer Data Connection 1-way FSI 2-5 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualConnecting Analysis Systems for FSI • Highlight desired ANSYS Analysis System in Toolbox and drag 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 systems Drag 1-way FSI 2-6 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training 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 systems 1-way FSI 2-7 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training 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 add 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 save Using Custom Systems = 1-way FSI 2-8 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training 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 improve 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 Mechanical • These are automatically created after the import 1-way FSI 2-9 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualImported Loads • In Mechanical an Imported Load entry will automatically be added to the tree when solution data is transferred from 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-down 1-way FSI 2-10 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training 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 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 – Not conservative – Interpolation process can be slow for large cases • Planning to enhance interpolation process in a future release 1-way FSI 2-11 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training Manual • Surface Temperature or Heat Transfer Coefficient (HTC) data 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 specify material properties for ANSYS Mechanical systems – Need to make sure thermal properties are consistent with CFD • Specific Heat, Thermal Conductivity, Density Thermal Transfer to Mechanical Systems 1-way FSI 2-12 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training Manual 1. Right-click on Imported Load (Solution) object in Outline panel 2. Select Insert > Temperature or Insert > Convection Coeff. 3. Choose a scoping method and corresponding CFD surface 4. For Convection Coeff., choose Near Wall Temperature or Ambient Temperature (see next slide) 5. Highlight Imported object to see contour and range Thermal Transfer to Mechanical Systems 1-way FSI 2-13 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualThermal Transfer to Mechanical Systems • If CHT has been solved in CFX, Temperature will be available on the 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 consistent with the way HTC was calculated in CFX – Wall Heat Transfer Coefficient is the variable imported from CFX 1-way FSI 2-14 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualThermal Transfer to Mechanical Systems • By default CFX will calculate Wall 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 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 temperature 1-way FSI 2-15 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualPressure 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 (Solution) and select Insert > Pressure 1-way FSI 2-16 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualThermal Stress Workflow Workflow 1: Thermal Data Only Transferred to Mechanical Workflow 2: Thermal and Pressure Data Transferred to Mechanical (A5 to C5 link added manually) 1-way FSI 2-17 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualThermal Stress Workflow 1. Solve CFD conjugate heat transfer (CHT) analysis for combined fluid and solid 2. Transfer surface temperatures/HTC to a Thermal analysis system – Solve temperature field 3. 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 FSI 2-18 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training Manual • Automotive Manifold – Full conjugate heat transfer solution in FLUENT – Cast iron solid material properties – Free stream external convection CFD Mesh ANSYS Mesh Thermal Stress Example 1-way FSI 2-19 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualThermal and Structural Loads Solid Temperature (CFD) Solid Temperature (ANSYS) Surface Pressure (CFD) Surface Pressure (ANSYS) 1-way FSI 2-20 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualANSYS Stress Solution Equivalent Stress Total Deformation Solution Metrics: 5 minutes to process all loads and solve ANSYS stress problem 1-way FSI 2-21 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualAlternative Thermal Stress Workflow 1. Solve CFD conjugate heat transfer (CHT) analysis for combined fluid and solid 2. Connect to a Structural analysis system – Optionally apply Pressure load from CFD results 3. Export a .cdb file from the Structural analysis 4. Use CFD-Post to write 3D solid Temperature field onto the .cdb file (beta feature) 5. Read .cdb file back into the Structural analysis system and solve for deformations (stresses) 1-way FSI 2-22 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualAlternative Thermal Stress Workflow • To export the .cdb file from Mechanical: – Insert a Command Snippet similar to that shown and Solve – The example shown refers to a Named Selection of solid bodies called SolidPart – This writes the .cdb file without solving the model due to the /EOF command – Use View > Files from the Project page to locate the .cdb file /PREP7 CMSEL,S,SolidPart NSLE,S,1 CDWRITE,DB,Export,cdb ALLS /EOF 1-way FSI 2-23 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualAlternative Thermal Stress Workflow • In CFD-Post: – First, set Edit > Options as shown – Restart CFD-Post Note: The Interpolation Tolerance controls the area or layer outside of the domain that is treated as part of the 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 Interpolation Tolerance should be increased. 1-way FSI 2-24 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualAlternative Thermal Stress Workflow • In CFD-Post: – Load fluid results – File > ANSYS Import/Export > Import ANSYS CDB Surface – Select file exported from Mechanical – Don’t 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, with Sampling = Vertex and Reduction Factor = 1 1-way FSI 2-25 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualAlternative Thermal Stress Workflow • In CFD-Post: – File > ANSYS Import/Export > Export ANSYS Load File – Select the Unit System you are using in Mechanical – Export Temperature to a .sfe file and place in the directory where the .cdb file 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 /SOLVE 1-way FSI 2-26 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training 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 • No built-in support for time-averaged data transfer 1-way FSI 2-27 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualTime-averaged Data Transfer – Thermal • Variables transferred from CFX to ANSYS are Wall Heat Transfer Coefficient or Temperature • To transfer 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 as usual to ANSYS 1-way FSI 2-28 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualTime-averaged Data Transfer – Structural • Transferring structural (pressure) data can use the same approach, but requires some additional steps • Boundary Flow data from the .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 Pressure.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 case 1-way FSI 2-29 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training 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 – Load step “End Time” must match “Analysis Time” for Imported Load Select time from drop-down list 1-way FSI 2-30 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training 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 transient load transfer – Faster and more accurate interpolation – But must run both codes simultaneously with a common time step – Steady-state cases can also be done 1-way • To use the GGI-based interpolation – See 2-way FSI chapter 1-way FSI 2-31 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualData Transfer from ANSYS to CFX • No automated transfer in Workbench yet • In Mechanical APDL use EXPROFILE command to generate profiles for CFX – Use Command Snippets or Mechanical APDL • Read into CFX-Pre like any other Profile Boundary • Surface quantities – Displacements (steady-state mesh morphing) – Temperature or heat flux • Volume quantities – Heat generation and potentially B-field for magnetohydrodynamics (MHD) • See ANSYS documentation, section 6.1 in the Coupled- Field Analysis Guide, or search for “EXPROFILE” 1-way FSI 2-32 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualData Transfer from ANSYS to CFX – Example • Solve modal analysis in ANSYS • Export the mode shape • CFX: transient analysis with prescribed mesh motion ANSYS Mode Shape Apply as Mesh Deformations in CFX-Pre CFD Results 1-way FSI 2-33 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualData Transfer from ANSYS to CFX – Example • Can use superposition method to combine mode shapes 1st mode 683 Hz 4th mode 3707 Hz2nd mode 1707 Hz 3rd mode 2248 Hz 1-way FSI 2-34 ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. July 2009 Inventory #002678 Training ManualData Transfer from ANSYS to CFX – Example • Can use superposition method to combine mode shapes   iiidisp tAx  .sin Ai : constant amplitude for i th mode i : frequency for i th mode i : i th mode shape Deformation, scaled by factor 200 31 32 33 34 35 36 37 0 0.001 0.002 0.003 0.004 Time [s] F o rc e [ N ] Amplitude 1 Amplitude 2 Normal force on blade