Lecture 6 Static Data Transfers. Solving FSI Applications Using ANSYS Mechanical and ANSYS Fluent Release. Release PDF Free Download

Lecture 6 Static Data Transfers 14. 5 Release Solving FSI Applications Using ANSYS Mechanical and ANSYS Fluent 1 2011 ANSYS, Inc. January 4, 2013

Outline Direct Project Schematic Connections Details on mapping CFD loads to Mechanical by connection cells on the project schematic External Data Connection to Mechanical This discusses using External Data to import loads to Mechanical External Data Connection to System Coupling Covers External Data connection to System Coupling, which can then connect to Fluent or Mechanical Appendix A: Loads files via Fluent Mapping Panels Appendix B: Manual Export from CFD-Post 2 2011 ANSYS, Inc. January 4, 2013

Direct Project Schematic Connections Supports surface Force, Temperature or HTC Supports volumetric Temperature transfer Does not support transfer from Mechanical to Fluent Interpolation is performed in the background by CFD-Post Automated and persistent workflow in a single WB project 3 2011 ANSYS, Inc. January 4, 2013

Integrated Process in Workbench Geometry CHT Mesh CFD CHT Solution Thermal Loads Pressure Loads Thermal Stress Solution 4 2011 ANSYS, Inc. January 4, 2013

Imported Loads In Mechanical an Imported Load entry will automatically be added to the tree when a Fluent Solution cell is connected to a Mechanical system Right-click on the Imported Load (Solution) to import: Pressure or Body Temperature load in a Structural system Temperature or Convection Coefficient surface load in a thermal system Select the Imported Pressure etc object to set the details (next slide) See the Imported Load Transfer Summary for details on the values transferred, including any unmapped nodes 5 2011 ANSYS, Inc. January 4, 2013

Imported Loads: Details panel 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 or zone names in the Fluent results file will be exposed via a drop-down Can only pick a single CFD region per Imported Load object 6 2011 ANSYS, Inc. January 4, 2013

Imported Loads: Viewing After setting the details and Generating the Imported Load object, select the Imported Pressure/Temperature etc object to view a contour or vector plot 7 2011 ANSYS, Inc. January 4, 2013

Imported Loads: Transfer Summary After Generating the Imported Load object, select the Imported Load Transfer Summary object to view details about the import Important to check for unmapped nodes and comparable values on the CFD and Mechanical sides 8 2011 ANSYS, Inc. January 4, 2013

Pressure Transfer to Mechanical Systems Pressure data is transferred from Fluent to a Mechanical Static/Transient Structural or Shape Optimization system Mechanical nodal values are calculated by linear interpolation from the surrounding CFD nodes Not conservative If interpolation process cannot find a face to map to, then closest point is chosen Mapping can be slow for large cases Octree mapper can be used instead (beta), discussed later 9 2011 ANSYS, Inc. January 4, 2013

Thermal Surface Transfer to Mechanical Surface Temperature or Wall Heat Transfer Coefficient data is transferred from Fluent to Mechanical via a Thermal system Static Thermal, Transient Thermal, Thermal Electric systems Solid temperature field will be solved in Mechanical If CFD results already have a solid temperature field, consider using a body load transfer to a structural system Make sure thermal material properties (specific heat, thermal conductivity, density) are consistent between CFD and Mechanical setups if the CFD solution included the solids 10 2011 ANSYS, Inc. January 4, 2013

Thermal Surface Transfer to Mechanical Can import Temperature or Convection Coefficient If conjugate heat transfer (CHT) has been solved in Fluent, Temperature will be available on the solid side and should be used Otherwise only the fluid-side temperature will exist, which should not be used, so choose Convection Coefficient 11 2011 ANSYS, Inc. January 4, 2013

Thermal Surface Transfer to Mechanical The Convection Coefficient uses Wall Heat Transfer Coefficient from CFD-Post This maps to Wall Func. Heat Tran. Coef in Fluent Choose CFD Near-wall Temperature as the Ambient Temp Type This is consistent with the way the HTC is calculated in Fluent After solving, check that the calculated surface temperatures in Mechanical match those in Fluent 12 2011 ANSYS, Inc. January 4, 2013

Thermal Surface Transfer to Mechanical Wall Func. Heat Tran. Coef, like a number of post-processing quantities in Fluent are not stored in the Fluent data file Many quantities are computed on-the-fly in Fluent To transfer a Convection Coefficient to Mechanical, Wall Func. Heat Tran. Coef must be output as an additional data quantity from Fluent Also a requirement to post-process Wall Heat Transfer Coefficient in CFD-Post Data file quantities panel is accessible via File > Data File Quantities or via Data File Quantities button in Run Calculation panel 13 2011 ANSYS, Inc. January 4, 2013

Heat Transfer Coefficients in Fluent Wall Func. Heat Trans. Coef. This is the HTC that is transferred to Mechanical Available for viscous flow, with energy solved but not Eulerian multiphase For multiphase/invisid cases schematic connections will not work for HTC For laminar flow is computed based on the Prandtl number (0.85 by default); in general this is not a good representation of the HTC For turbulent flow this HTC is based on wall functions The reference temperature is the adjacent cell temperature (named Wall Adjacent Temperature in CFD-Post) 14 2011 ANSYS, Inc. January 4, 2013

Heat Transfer Coefficients in Fluent Surface Heat Transfer Coef. Available for viscous flow, with energy solved but not Eulerian multiphase To use this HTC use one of other approaches discussed later Calculated based on the boundary heat flux, the outer wall temperature and the reference temperature: Surface Heat Transfer Coef. = q / (T WALL -T REF ) where T REF is set on the Reference Values panel in Fluent T REF = Local cell temperature Note: This can be evaluated using Custom Field Function of (Total Heat Surface Heat Flux - Radiation Heat Flux) / (Wall Temperature (Outer Surface) - Static Temperature) and plotting without node values 15 2011 ANSYS, Inc. January 4, 2013

Heat Transfer Coefficients in Fluent Custom Surface HTC based on adjacent cell temperature A Custom Field Function can be used to calculate the following HTC HTC = (Total Heat Surface Heat Flux - Radiation Heat Flux) / (Wall Temperature (Outer Surface) - Static Temperature) Like Surface Heat Transfer Coef., this HTC is based on the boundary heat flux, but the reference temperature used here is the adjacent cell temperature It gives exactly the same HTC values as Wall Func. Heat Trans. Coef. Can be calculated when energy is solved To use this HTC use one of other approaches discussed later 16 2011 ANSYS, Inc. January 4, 2013

Comparing Fluent HTC s T REF =T INLET Adjacent Cell Temperature Surface Heat Transfer Coef. = Wall Func. Heat Trans. Coef Custom HTC based on adjacent cell temp. 17 2011 ANSYS, Inc. January 4, 2013

Surface Data Mapping CFD-Post performs the mapping process for vector and scalar quantities Mechanical nodal values are transferred by linear interpolation from the surrounding CFD face nodes If the interpolation process cannot find a face to map to, then the closest point is chosen The mapping is not conservative The interpolation process can be slow for large cases An octree surface mapping option (beta) is available to speed up surface mapping 18 2011 ANSYS, Inc. January 4, 2013

Octree Surface Mapper Surface mapping option (beta) to speed up surface mapping Turn on Edit > Options > CFD-Post > Enable Beta Features and Enable Octree FSI Surface Mapping Octree mapping will then be used for surface transfers from CFX or Fluent to Mechanical (via Workbench and via Post manually) Must set this option in CFD-Post then restart CFD-Post 19 2011 ANSYS, Inc. January 4, 2013

Octree Surface Mapper The algorithm creates 3D elements by extruding the CFD boundary mesh in the surface normal direction These 3D elements are called the virtual layer Structural nodes that lie inside the CFD domain or inside the virtual layer are mapped In general, the thinnest virtual layer that ensures all nodes are mapped will provide the best results 20 2011 ANSYS, Inc. January 4, 2013

Octree Surface Mapper Set Layer Tolerance by either: Percentage of Domain Extents If the domain extents are 50[m], setting the Layer Tolerance to a value of 0.5, would result in a Layer Thickness = ( 0.5 / 100 ) * 50 = 0.25[m] Setting the value in this way is useful for cases with coarse CFD meshes Percentage of Average Face Extents If the average of all boundary face extents is 0.2[m], setting the Layer Tolerance to a value of 20 would result in a Layer Thickness = (20 / 100) * 0.2 = 0.04[m] Setting the value in this way is useful for cases with finer CFD meshes, or for cases with mesh refinement 21 2011 ANSYS, Inc. January 4, 2013

Octree Surface Mapper Only surfaces that are closely aligned will be mapped For Temperature transfer, data is mapped from the Fluent nodes to the Mechanical nodes (i.e. the DOF is specified directly in Mechanical) Unmapped nodes are assigned the average domain Temperature For Heat Flux, HTC and Stress vector transfer, data is mapped from the Fluent nodes to surface element faces in Mechanical The surface element receives the average value of the Fluent nodes mapped to that face Only the Fluent nodes that are mapped contribute to the average If no nodes are mapped for a given element face, a zero value/vector is sent 22 2011 ANSYS, Inc. January 4, 2013

Thermal Body Load Transfer to Mechanical Temperature body loads are transferred from Fluent to a Mechanical Static/Transient Structural or Shape Optimization system to perform a thermal stress analysis Solve CFD CHT analysis for combined fluid and solid Connect to a structural system and insert a Body Temperature Can only select a single Fluent solid zone per import Can also insert a surface Pressure load if necessary 23 2011 ANSYS, Inc. January 4, 2013

Thermal Body Load Transfer to Mechanical After importing the load, check the transfer summary In particular, check for unmapped nodes Unmapped nodes are currently assigned the average domain temperature Adjusting the Interpolation Tolerance in CFD-Post can usually avoid un-mapped nodes Start CFD-Post: Edit > Options > CFD-Post Is saved as a preference when CFD-Post is closed 24 2011 ANSYS, Inc. January 4, 2013

Thermal Body Load Transfer to Mechanical CFD-Post creates a virtual layer of elements around the edges of the CFD domain when performing the mapping Structural nodes that lie inside the CFD domain or inside the virtual layer are mapped The Interpolation Tolerance controls the size of the virtual layer. The default is 0.5% of the CFD domain extent. Increasing the Interpolation Tolerance may allow un-mapped structural nodes to fall inside the virtual layer For some geometries with sharp edges (e.g. cooling fins) a virtual layer that is too thick produces highly skewed virtual elements that cause the interpolation to fail Reducing the Interpolation Tolerance can help here 25 2011 ANSYS, Inc. January 4, 2013

Alternative Thermal Stress Workflow Instead of passing a Body Temperature to a Structural system, thermal stress can also be solved by passing a surface temperature/htc to a Mechanical Thermal system, solving the solid volumetric temperature, then passing the Body Temperature to the Structural system Thermal surface transfer from fluid to thermal system Thermal body transfer from thermal to structural system Optional Pressure surface transfer from fluid to structural system 26 2011 ANSYS, Inc. January 4, 2013

Thermal Surface Load vs Body Load Transferring a body load directly to a structural system avoids the need for re-solving the temperature field in a Mechanical thermal system When to consider using a surface load transfer: Mapping algorithms are different. Surface mapping provides another route if there are problems with the volume temperature mapping If you haven t solved CHT in the fluid system, then only Wall HTC data is available so must use surface mapping However, the wall temperature used in Fluent to generate the HTC will not have been exactly correct Can export the wall temperature from Mechanical, import into Fluent and re-solve to get a more accurate HTC Will need to iterate towards a converged HTC 27 2011 ANSYS, Inc. January 4, 2013

Time-Averaged Data Transfer Time-averaged data is useful for many different applications Averaged pressure loads from transient CFD LES, DES, Multiphase etc. Averaged HTC or Temperature loads from transient CFD Turbine blade cooling, cylinder heads, electronic cooling, furnaces etc. No built-in support for timeaveraged data transfer 28 2011 ANSYS, Inc. January 4, 2013

Time-Averaged Data Transfer Variable names transferred from Fluent to Mechanical are: Wall Func. Heat Tran. Coef, Pressure and Temperature To transfer a time-averaged quantity: Use Fluent UDF to over-write variables in Fluent data file with time averaged quantities (sample outline shown) Transfer data as usual to Mechanical Refer to Fluent UDF manual and/or tutorials for further information 29 2011 ANSYS, Inc. January 4, 2013

Example: Time-Averaged Data Transfer Cycle Averaged Temperature Data Instantaneous Temperature Data 30 2011 ANSYS, Inc. January 4, 2013

Example: Time-Averaged Data Transfer For this example, two UDF macros are used DEFINE_EXECUTE_AT_END This fills user-defined memory (UDM) locations with summated and averaged quantity values (i.e. temperature) User defines and controls UDM DEFINE_ON_DEMAND This overwrites cell and face instantaneous quantities with the averaged values from userdefined memory (UDM) Save new Fluent data file such that new timeaveraged values can be transferred to Mechanical This macro is invoked at end of cycle Execute at End Function Hook Execute on Demand 31 2011 ANSYS, Inc. January 4, 2013

Using Transient CFD Results Data from Transient CFD results can be transferred to steady state and transient Mechanical systems A single Source Time can be selected from a drop-down list when the Imported <Variable> is highlighted in Outline panel By default, the last time step is used Load step End Time must match Analysis Time for Imported Load Fluent data sets must be complete Partial data (i.e. cdat) is not supported for imported loads Not practical for many time steps Need an Imported Load for each time step Load mapping repeated n times slow Select time from drop-down list 32 2011 ANSYS, Inc. January 4, 2013

Using Transient CFD Results Other approaches for 1-way Transient FSI: 1. Use co-simulation; send data only 1- way This is the preferred approach when possible Automated load transfer; faster and more accurate mapping Must run both codes simultaneously with a common time step In System Coupling the Data Transfers can be suppressed or deleted to easily switch to a 1- way analysis 2. Use External Data see next section 33 2011 ANSYS, Inc. January 4, 2013

Using Transient CFD Results 3. Use ACT (Application Customization Toolkit) extension to automate load file creation for all time steps and reading them in during the Mechanical solution Contact support for further information 34 2011 ANSYS, Inc. January 4, 2013

External Data Component The External Data Component allows data to be imported into ANSYS Mechanical from an external ASCII file Supports volumetric/surface Temperature, Pressure, HTC, Heat Flux, volumetric Heat Generation and Displacement b Can be used as an alternative to the standard 1-way mapping Export a data file from CFD-Post, Fluent or elsewhere, then import via External Data 36 2011 ANSYS, Inc. January 4, 2013

Consider Using External Data When You want to map a non-standard variable, e.g. a transient average You want to perform 2D mapping to Mechanical The External Data mapping algorithms are preferred to those of CFD-Post You want to use lower resolution data from CFD results instead of mapping every node Create a Point Cloud in CFD-Post then export data Fluid and structural geometries are in different coordinate frames Export data using a local coordinate frame in CFD-Post or apply transformations in External Data 37 2011 ANSYS, Inc. January 4, 2013

Consider Using External Data When You want to edit the exported data before import to Mechanical You want to perform a transient 1-way FSI simulation in Mechanical A workflow based on a single project is not convenient E.g. fluid and structural groups using different Workbench projects You don t have a CFD-Post license available when importing the data into Mechanical The interpolation is too slow using the standard approach Could also use the Point Cloud method to speed up 38 2011 ANSYS, Inc. January 4, 2013

External Data Component The main disadvantage of using External Data is that the workflow is disconnected no automatic data updates The External Data uses the mapping algorithms built into ANSYS Mechanical rather than the mapping based on CFD Post 39 2011 ANSYS, Inc. January 4, 2013

External Data Approach: Export 1. Load the CFD Results file into CFD Post 2. Select File > Export External Data File Pick the Location that you wish to export data for and select the variables that you wish to export for the external data transfer Formatting is more automated in External Data when using this file format OR Select File > Export To perform a generic export, making sure Export Geometry Information is checked Export of volumetric quantities must be done this way 40 2011 ANSYS, Inc. January 4, 2013

Notes for Generic File > Export Line 7 When using the generic File > Export the csv file that you export from CFD-Post includes a header which shows the variables that have been exported along with their units. When you read the file into External Data, be sure to skip the header and start the import at the first line of the actual data You will need to tell External Data what quantity each column represents This is automated when using the External Data (.axdt) file format 41 2011 ANSYS, Inc. January 4, 2013

Adding an External Data Component Drag an External Data Component system on the Project Schematic Link the Setup cell of the External Data system to the Setup cell of Mechanical system which will receive the data Edit the Setup cell of the External Data system to specify the file and the data that will be imported 42 2011 ANSYS, Inc. January 4, 2013

Specifying the External File for Import Inside the External Data system, click in the Location field to select the file for import Browse to select the file Note that multiple files can be selected here by using the Ctrl key 43 2011 ANSYS, Inc. January 4, 2013

Setting the File Format and Delimiter The Format Type will be AXDT if an External Data file was exported nothing else needs setting For other files, including CFD-Post csv files: Set the format type to Delimited and the Delimiter Type to Comma Set the Start Import At Line correctly if the file includes a header (line 7 in this case) Can transform the x, y, z coordinates here Check the preview to see if the data imported is correct z [m] Tnw [K] h [W/m^2/K] x [m] y [m] 44 2011 ANSYS, Inc. January 4, 2013

Setting the Data Columns For AXDT files the Data Type and Data Units will have been automatically set, but should be checked For other files types click in the drop-downs under Data Type to correctly set the variable contained in each of the columns and set the correct units under Data Units In the Project Schematic Update the External Data Setup cell 45 2011 ANSYS, Inc. January 4, 2013

Importing the External Load When you open Mechanical, the imported load will appear in the Model tree To insert the load, rightclick on the Imported Load entry and choose Insert > and the appropriate load For a thermal system, choices include Heat Flux, Heat Generation, Temperature and Convection Coefficient 46 2011 ANSYS, Inc. January 4, 2013

Convection Coefficient When importing a Convection Coefficient, Mechanical expects both an Ambient Temperature and a Heat Transfer Coefficient in the input file Make sure the Ambient Temperature is consistent with that used when calculating the HTC - see earlier discussion on HTC s in Fluent 47 2011 ANSYS, Inc. January 4, 2013

Scaling and Offset In Mechanical a Scale factor and an Offset value can be applied to the incoming data values Recall that coordinate transforms are applied in External Data, but data transforms are applied here in Mechanical 48 2011 ANSYS, Inc. January 4, 2013

Displaying the Mapped Data To import load, right click on the imported load and choose Import Load If the imported data contains more than one field (i.e. Convection Coefficient and Ambient Temperature), you can choose which is displayed using the Data field in the Details view for the imported load 49 2011 ANSYS, Inc. January 4, 2013

Displaying the Mapped Data After import, can right-click on the imported load to Export the mapped data to a txt file Set Displace Source Points to On to show the data points from External Data on the model 50 2011 ANSYS, Inc. January 4, 2013

Mapping Controls Mapping Controls available in Mechanical Weighting (smoothing) algorithm options: Triangulation: Good default. Can give poor results if target points not found within the source point cloud Kriging: Regression-based interpolation technique that can give smoother mapping Distance Based Average: Simple robust method which can give a mapping when other weightings fail See Mechanical Applications doc: // Mechanical User Guide // C. Data Transfer Mesh Mapping Triangulation versus Kriging smoothing 51 2011 ANSYS, Inc. January 4, 2013

Checking Mapped Nodes When data is mapped to nodes (as opposed to surface elements), an option is available to create a Named Selection based on: Unmapped Nodes: All target nodes in Mechanical that cannot be mapped Mapped Nodes: All target nodes in Mechanical that were mapped Outside Nodes: All nodes that cannot be found within tetrahedrons when using the Triangulation weighting algorithm (these nodes would default to the Distance Based Average weighting) 52 2011 ANSYS, Inc. January 4, 2013

Mapping Validation Right-click on an Imported Load to insert a Validation object and set the Type See next slide for details Turn Display In Parent On to show the validation data when the parent imported load object is selected (example on next slide) 53 2011 ANSYS, Inc. January 4, 2013

Mapping Validation Reverse Mapping: maps the data back to the source and shows the difference Distance Based Average Comparison: maps using the simple distance weighted algorithm and then compares to the data mapped using the currently selected mapping method Source Value: displays the source data points and values Undefined Points: unmapped nodes Reverse Mapping differences overlaid with mapped data (Display In Parent = On) Source Value validation draws source load values directly on model 54 2011 ANSYS, Inc. January 4, 2013

Transient Cases with External Data Transient 1-way FSI to Mechanical is performed by importing load files for a number of time steps into External Data Do not process files one at a time! Multi-select files for all time steps when importing Multi-select imported files when setting properties Follow documented procedure: // User's Guide // Systems // Component Systems // External Data // Importing Multiple Data Sets No requirements to use the same time step in CFD and FEA 55 2011 ANSYS, Inc. January 4, 2013

Multiple Data Sets and Master File Importing multiple load files is also useful when you are mapping to many different bodies/surfaces When dealing with multiple files, if all files have the same X,Y,Z coordinate data (e.g. transient case), designating one file as the Master will greatly speed up mapping Mapping weights are only calculated once, then re-used 56 2011 ANSYS, Inc. January 4, 2013

External Data to System Coupling An External Data to System Coupling connection provides steady-state 1-way thermal transfers: One-way transfer of Heat Flow or Temperature to Fluent via External Data One-way transfer of Heat Flow, Temperature or Heat Transfer Coefficient to Mechanical via External Data External Data can be used to provide static thermal data to either Fluent or Mechanical 58 2011 ANSYS, Inc. January 4, 2013

External Data to System Coupling Why have another method for 1-way thermal transfers? A step towards 2-way and 1-way transient thermal transfers in version 15.0 Can transfer data to either Fluent or Mechanical Other methods only transfer to Mechanical Can perform a series of 1-way transfers to get a 2-way solution Provides access to System Coupling features, e.g. the conservative mapping algorithm for conserved quantities (Heat Flow) 59 2011 ANSYS, Inc. January 4, 2013

Workflow Example 1 1. External Data file (.axdt) from an existing analysis provides Temperature boundary data to Fluent via System Coupling 2. After solving Fluent, HTC and Near Wall Temperature are exported to a.axdt file an read into External Data 3. Mechanical solves using the Fluent HTC boundary data and exports a.axdt file containing Temperature 4. Repeat 1 3 as necessary AXDT File AXDT File AXDT File 2 3 60 2011 ANSYS, Inc. January 4, 2013

AXDT File The AXDT file is a simple text file format File contains node locations, thermal data and element face data from the source mesh Face data is necessary to allow conservative data transfer AXDT files can be created by: Export from CFD-Post Automatically written at the end of a Steady-State Thermal analysis Using Excel or output from other solvers/post-processors 61 2011 ANSYS, Inc. January 4, 2013

AXDT Export from CFD-Post Use File > Export > Export External Data File in CFD-Post Fluent or CFX results For CHT results pick the Location carefully Typically want the solid side when exporting Temperature but the fluid side for HTC and Wall Adjacent Temperature Heat Flow won t be available on interface regions in Fluent results 62 2011 ANSYS, Inc. January 4, 2013

AXDT Export from CFD-Post Recommend variables are presented HTC and Wall Adjacent Temperature: uses Wall Heat Transfer Coefficient (which is based on Wall Func. Heat Trans. Coef) and its associated reference temperature. Fluent does not calculate this for laminar or Eulerian mutliphase Heat Flow: this is a conservative quantity Temperature Can also select your own variables if necessary 63 2011 ANSYS, Inc. January 4, 2013

AXDT Export from Steady-State Thermal On a Fluid Solid Interface the Export Results option (default is Yes) triggers a macro (dumpfsiheats.mac) that writes out the AXDT file after the solve File written to the directory containing the Thermal solution Named fsin_#.axdt, where # corresponds to the Interface Number Contains Temperature and Heat Flow Turn off when export is not needed can be slow for large cases 64 2011 ANSYS, Inc. January 4, 2013

Load AXDT File into External Data Edit External Data Setup and specify the AXDT file Follow the same process as discussed earlier in the External Data Connection to Mechanical section Connect the External Data Setup cell and either the Fluent or Steady-State Thermal Setup cell to the System Coupling Setup cell 65 2011 ANSYS, Inc. January 4, 2013

Define Regions to Receive the Data To define the location that will receive the thermal data: In Mechanical create a Fluid Solid Interface In Fluent use the via System Coupling option as the Thermal condition on a Wall boundary 66 2011 ANSYS, Inc. January 4, 2013

System Coupling Setup Update the upstream Setup cells then Refresh and Edit the System Coupling Setup cell External Data regions and regions that can receive data in Mechanical/Fluent are listed in System Coupling Multi-select regions and rightclick to create Data Transfers as usual Enable beta features to allow 1-to-many Data Transfers i.e. a single External Data region to many Fluent or Mechanical boundaries 67 2011 ANSYS, Inc. January 4, 2013

System Coupling Setup Since this is 1-way FSI, under System Coupling Analysis Settings use a single Coupling Iteration If multiple steps are used then MAPDL will ramp the load linearly over the Number of Steps for a Steady-State analysis Update the System Coupling Solution cell to solve the case 68 2011 ANSYS, Inc. January 4, 2013

System Coupling Solution Mapping is performed at runtime by System Coupling Check the Mapping Summary in the output as usual Temperature and HTC use Profile Preserving mapping, Heat Flow uses Conservative mapping Same debug controls E.g. DumpInterfaceMeshes or DTDiagShowAll to show additional mapping diagnostics (beta) Loads are passed to Fluent or MAPDL solver at run-time 69 2011 ANSYS, Inc. January 4, 2013

Summary There are a number of workflows for transferring static data between Fluent and Mechanical For Fluent to Mechanical data transfer, the direct schematic connections are easy to use and are often the first choice Using External Data provides more workflow flexibility since there s no need for a single project and it extends easily to transient 1-way Fluent to Mechanical cases The External Data connection to System Coupling allows data to be passed from Mechanical to Fluent in addition to Fluent to Mechanical and provides conservative Heat Flow mapping 70 2011 ANSYS, Inc. January 4, 2013

Fluent Mapping Panels Supports thermal and structural loads for surfaces and volumes Temperature, Heat Transfer Coefficient (Wall Function, Adjacent Cell Temperature and Reference Temperature), Heat Flux, Pressure, Force Efficient interpolation to structural mesh in Fluent Workflow is not automated or persistent by default But can be scripted in WB 72 2011 ANSYS, Inc. January 4, 2013

Fluent Mapping Panels Uses libraries from Visual Kinematics Inc. (VKI) to read and write FEA file formats Libraries also allow FEA mesh to be displayed in Fluent For each FEA node/element a binary search partition (BSP) tree algorithm is used to find closest node in Fluent mesh Example: Find the point on the curved line which is closest to the blue point BSP tree Data is then interpolated from the closest node 73 2011 ANSYS, Inc. January 4, 2013

Fluent Mapping Panels Scripting and Command Snippets can be used to automate the workflow See workshop for example Consider using the Fluent mapping panels: If you are using Fluent outside of Workbench and wish to generate load files for Mechanical/MAPDL To generate load files for non-ansys FEA solvers If mapping using the CFD-Post algorithms produces unmapped nodes that cannot be corrected or is slow See Fluent documentation for further details: // User's Guide :: 2 // 4. Reading and Writing Files // 4.20. Mapping Data for Fluid-Structure Interaction (FSI) Applications // 4.20.2. Using the FSI Mapping Dialog Boxes 74 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping The project schematic connection approach is launching CFD-Post in the background to perform the mapping Can use CFD-Post to manually generate a load file, for example when using Mechanical APDL: Write out a.cdb file containing the Mechanical surface or volume mesh Load the.cdb and CFD results files into CFD-Post then export a load file Read the load file into Mechanical The following slides describe how to do this in Workbench Generally not necessary, but could be used to apply a load from a CFD solution that is not in the current project or apply a heat flux (which is not supported via the direct connections) The commands shown can be applied in MAPDL 76 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping Write out the.cdb file from Mechanical/ APDL using the CDWRITE command: For Mechanical in WB, can insert a Command Snippet similar to that shown and Solve The example shown for Temperature body mapping refers to a Named Selection of solid bodies called SolidPart This writes the.cdb file without solving the model due to the /EOF command Note that you ll get a solution error when running in WB, but it creates the.cdb file Comment out the CDWRITE and /EOF commands or Suppress the snippet when you come to really solve Use View > Files from the Project page to locate the.cdb file /PREP7 CMSEL,S,SolidPart NSLE,S,ACTIVE CDWRITE,DB,Export,cdb ALLS /SOLU /EOF 77 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping To write out a.cdb file for Pressure (stress vector) surface mapping, create a layer of SURF154 elements on the boundary of interest This example refers to a Named Selection interface_solid_side Comment out the CDWRITE and /EOF commands when really solving Don t suppress the snippet since the surface elements need to get created when solving /PREP7 ET,100,SURF154 CMSEL,S,interface_solid_side TYPE,100 ESURF ESEL,S,TYPE,,100 CDWRITE,DB,exported_surface,cdb ALLSEL /SOLU /EOF 78 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping To write out a.cdb file for HTC or Heat Flux surface mapping, use the same procedure as Pressure but use SURF152 elements For HTC, associate with the fluid side of a CHT interface when importing into CFD-Post For Heat Flux associate with the solid side To write out a.cdb file for Temperature surface mapping, there's no need to create surface effect elements since Temperature will be the DOF and is set directly Pick the solid side of a CHT interface when importing into CFD-Post /PREP7 ET,100,SURF152 CMSEL,S,interface_solid_side TYPE,100 ESURF ESEL,S,TYPE,,100 CDWRITE,DB,exported_surface,cdb ALLSEL /SOLU /EOF /PREP7 CMSEL,S,interface_solid_side NSLE,S,ACTIVE CDWRITE,DB,exported_surface,cdb ALLSEL /SOLU /EOF Comment out the CDWRITE and /EOF commands when solving 79 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping Open CFD-Post with the fluid results of interest Load the.cdb file using File > Import > Import Mechanical CDB Surface For surface select the associated CFD boundary Can only pick one For volumes disable Specify Associated Boundary 80 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping After importing the.cdb file a User Surface object will be created in CFD-Post For surface mapping you can enable the visibility and view the mesh using the usual Render options For volume mapping enabling the visibility will not show the Mechanical volume mesh Instead create a Point Cloud object scoped to the User Surface with Sampling = Vertex and a Reduction Factor of 1 to see the node locations For Pressure loads, can plot the Stress Vector in CFD-Post by creating a new Vector Variable and assigning the components as Force X/Area, Force Y/Area and Force Z/Area 81 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping Export the load file from CFD-Post using File > Export > Export Mechanical Load File For Stress, Heat Flux and HTC the load file will contain SFE commands to apply loads via the SURF152/154 elements For Temperature a surface load file will contain D commands to set the DOF A Temperature body load file will contain BF commands Must export in Celsius A structural analysis reads BF loads in Celsius regardless of the units selection in WB Can open the exported file in a text editor and make sure the values look reasonable 82 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping Read the load file into Mechanical In Workbench can either paste the contents into a Command Snippet or read in the file while solving using the /input command in a Command Snippet!/input,file name,file extension,'c:\file path! For example: /input,pressure,sfe,'c:\users\username\project Make sure your solution units are consistent with the values exported from CFD-Post In particular, Mechanical is Celsius by default while Fluent is Kelvin After solving check the Solution Information and.err file to make sure the /input command was successful. If the file was not read the solution will still proceed without the load applied 83 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping After solving can visually check the applied load in Mechanical For an imported Temperature body load: Selection Solution Click Worksheet Find the Type = BFE, Output Unit = Temperature entry Right-click and select Create User Defined Result A BFE entry appears under Solution to show the imported temperature load 84 2011 ANSYS, Inc. January 4, 2013

Manual 1-way Mapping After solving can visually check the applied load in Mechanical For an imported surface load, insert a Command Snippet into the structural setup as shown See the doc for /PSF command options for Heat Flux, Convection Coefficient and Pressure CMSEL points to a Named Selection Insert an empty Command Snippet below Solution; the plot will appear as an object below this! --- set view position /VIEW,,1,1,-1! --- reverse video /RGB,INDEX,100,100,100, 0 /RGB,INDEX, 80, 80, 80,13 /RGB,INDEX, 60, 60, 60,14 /RGB,INDEX, 0, 0, 0,15! --- turn on pressure load contours /PSF,PRES,NORM,3,0,1! --- display to png image /SHOW,PNG! --- element display CMSEL,S,interface_solid_side ESLN,R,1 EPLOT ALLSEL 85 2011 ANSYS, Inc. January 4, 2013

Exporting csv Files from CFD-Post CFD-Post can also be used to export data to text files (.csv) E.g. export CFD nodal pressures for use with External Data (discussed in the next section) Since CFD-Post can read Mechanical results, it can also be used to export displacements for Fluent Use in Fluent like any other profile boundary The EXPROFILE command also exports data from Mechanical results (discussed in the last section) 86 2011 ANSYS, Inc. January 4, 2013

Lecture 6 Static Data Transfers. Solving FSI Applications Using ANSYS Mechanical and ANSYS Fluent Release. Release 14.5