ACU-T: 1000 HyperWorks CFD UI Introduction

This tutorial introduces you to the workflow for setting up a Computational Fluid Dynamics (CFD) analysis using Altair HyperWorks CFD. HyperWorks CFD is a powerful tool which provides a streamlined platform for performing a CFD analysis, starting from importing CAD through solving using Altair AcuSolve. In this tutorial, you will learn how to use HyperWorks CFD for setting up a CFD analysis while exploring different capabilities available within the software for importing a geometric model, validating the geometry, setting up simulation parameters and boundary conditions, and generating a mesh. You will then launch AcuSolve simulation directly from HyperWorks CFD and post-process the results using Altair HyperView.

Prerequisites

To run this simulation, you will need access to a licensed version of HyperWorks CFD and AcuSolve.

Prior to running through this tutorial, copy HyperWorksCFD_tutorial_inputs.zip from <Altair_installation_directory>\hwcfdsolvers\acusolve\win64\model_files\tutorials\AcuSolve to a local directory. Extract ACU-T1000_manifold.x_t from HyperWorksCFD_tutorial_inputs.zip.

Analyze the Problem

An important step in any CFD simulation is to examine the engineering problem at hand and determine the important parameters that need to be provided to AcuSolve. Parameters can be based on geometrical elements, such as inlets, outlets, or walls, and on flow conditions, such as fluid properties, velocity, or whether the flow should be modeled as turbulent or as laminar.

The system being simulated here is a manifold pipe, analogous to an inlet manifold in an engine. An inlet manifold distributes the incoming flow to multiple outputs. As can be seen in the image below, the pipe has a single inlet and multiple outlets, thus distributing a fraction of the flow among each outlet. Ideally in an inlet manifold used in an engine, the manifold design is such that it ensures near-equal distribution of flow among all the outlets. However, the geometry being used here is purely a demonstration case and not an optimized manifold geometry.


Figure 1. Schematic of the Problem

Introduction to HyperWorks CFD



Figure 2.
The tools and entities displayed in the HyperWorks CFD graphical user interface can be divided into six general categories as shown in the figure above.
  1. Menu bar
  2. Ribbons
  3. Modeling window
  4. Entity selector
  5. View Controls toolbar
  6. Browsers
  1. The menu bar (1) contains the drop-down menus for File input-output, Edit, and View operations.
  2. Ribbons (2) contain various functionalities and tools available in HW-CFD. Navigate between various ribbons by clicking the ribbon tabs to the right of the menu bar. After selecting a ribbon, the corresponding tool icons are displayed on the screen. The functionalities of various ribbons and corresponding tools are briefly explained in this section.
    Geometry ribbon
    The Geometry ribbon consists of tools for converting, repairing, creating, editing, and validating the geometry. The tools available under the FE Geometry sub-section can be used to convert a geometry model to an FE model, cap the openings automatically, define local or proximity-based wrap controls, wrap the model, remesh the wrapped results, and fix the mesh quality.


    Figure 3.
    When a geometry file is imported, the Repair tools can be used to detect any defects present in the CAD model like intersections, free edges, duplicates, sliver surfaces, etc. and fix those errors.


    Figure 4.
    The tools available under the Create sub-section can be used to create geometric entities like points, lines, surfaces, etc.


    Figure 5.
    The tools required for performing operations like plugging cavities, stitching surfaces, etc. are available under the Edit sub-section.


    Figure 6.
    The Defeature tool can be used to resolve these defects or model a new geometry, while the Validate tool can be used to detect any defects present in the CAD model. This process is usually known as CAD cleanup.


    Figure 7.
    Flow ribbon
    The Flow ribbon contains tools for setting up simulation parameters, solver settings, and reference properties such as material properties, heat sources, porous media, etc. The Setup sub-section is where you set up the physics equations and solver settings as well as create material models, multiplier functions, and parameters.


    Figure 8.
    The Domain sub-section contains tools for assigning reference properties such as materials, heat and momentum sources, reference frames, etc. to volumes.


    Figure 9.
    Surface boundary conditions such as inlets, outlets, far fields, etc. can be assigned using the tools under the Boundaries sub-section. By default, all the surfaces are assigned a boundary condition of type ‘auto_wall’ and are placed under Default wall. Please refer to the AcuSolve Surface Processing manual for more information about auto_wall. As you assign boundary conditions to the surfaces, they are moved into the respective group.


    Figure 10.
    Radiation ribbon
    The Radiation ribbon is where you define radiation physics, create thermal, solar, and participating media models, and apply radiation parameters.


    Figure 11.
    Motion ribbon
    Mesh boundary conditions and mesh-motion-related parameters can be defined using the tools available in the Motion ribbon. Parameters such as mesh motion type and mesh displacement constraints can be defined here.


    Figure 12.
    Mesh ribbon
    Meshing parameters such as surface mesh controls, boundary layer parameters, volume mesh parameters, and zone meshing parameters can be defined here. This ribbon also has tools for local remeshing. Once all the mesh controls are defined, you can generate the mesh using the Batch tool.


    Figure 13.
    Solution ribbon
    The Solution ribbon is used to set up monitors for any individual point, surface, or volume set output. The Field tool is used to set the nodal output frequency for the entire model. The Initialize tools are used to set the nodal initial conditions for variables like pressure, velocity, and variables specific to each turbulence model.


    Figure 14.

    Once the complete set up is done, the Run tool is used to launch AcuSolve. Once the AcuSolve run parameters are set, the simulation can be started, and you can monitor the status of the run using the run manager.

  3. The modeling window (3) is where the model is displayed. The model display can be manipulated using the view controls shown in the table below. Clicking on the model will highlight the entity being selected and right-clicking on an entity will give you additional options for the operations that can be done based on the context. Some of the functions available using right-click are Show, Hide, Isolate, Select, Advanced select, Create groups, etc.
    Button Operation
    Middle mouse scroll Zoom in and out
    Right-click hold and drag Pan the model
    Middle mouse click hold and drag Rotate the model
    Left-click Select entity
    Ctrl + Left-click Select multiple entities
    Left-click hold and drag Window select
    Shift + Left-click Deselect entities
  4. The entity selector (4) enables you to control what entities can be selected using the left-mouse button. The selector can be set to any of the entities shown in the figure below. When you open any tool, the selector is automatically set to the entity (entities) which are appropriate for that command.


    Figure 15.
  5. The visualization of the model can be controlled using the tools available in View Controls toolbar (5). The display of mesh, model display mode (e.g. Topology, part, assembly, etc.), section cuts, standard views, etc. can be controlled using these tools.


    Figure 16.
  6. The Part Browser and Setup Browser (6) show all the entities and setup parameters in the model and list them in a tree structure. Both can be turned on or off from the View menu. Some common functions that can be performed in the both browsers are show, hide, and isolate. The Part Browser can be used to manage the model's parts, surface bodies, and solid bodies while the Setup Browser can be used to create and edit instances of model setup parameters such as boundary conditions, domains, mesh controls, etc.

This tutorial uses Altair HyperView for post-processing the results. For detailed information about the user interface of HyperView, please refer to the HyperMesh introductory tutorial, Introduction to HyperView.

Start HyperWorks CFD and Create the HyperMesh Model Database

  1. Start HyperWorks CFD from the Windows Start menu by clicking Start > Altair <version> > HyperWorks CFD.
    When HyperWorks CFD is loaded, the Geometry ribbon is open by default.
  2. Create a new .hm database in one of the following ways:
    • From the menu bar, click File > Save.


      Figure 17.
    • From the Home tools, Files tool group, click the Save As tool.


      Figure 18.
  3. In the Save File As dialog, navigate to the directory where you would like to save the database.
    This will be your problem directory and all the files related to the simulation will be stored in this location.
  4. Enter a name for the database (eg. Manifold) then click Save.

Import and Validate the Geometry

Import the Geometry

Before you start this step, copy the input file, ACU-T1000_manifold.x_t, to your problem directory.
  1. From the menu bar, click File > Import > Geometry Model.
  2. In the Import File dialog, browse to your working directory then select ACU-T1000_manifold.x_t and click Open.
  3. In the Geometry Import Options dialog, leave all the default options unchanged then click Import.


    Figure 19.
  4. Once the geometry is loaded, rotate and observe the features of the model.
    The view of the model displayed in the modeling window can be controlled using the following view controls.
    Button View Control
    Middle mouse scroll Zoom in and out
    Right-click hold and drag Pan the model
    Middle mouse click hold and drag Rotate the model


    Figure 20.

Validate the Geometry

  1. From the Geometry ribbon, click the Validate tool.


    Figure 21.
    The Validate tool scans through the entire model, performs checks on the surfaces and solids, and flags any defects in the geometry, such as free edges, closed shells, intersections, duplicates, and slivers.

    The current model doesn’t have any of the issues mentioned above. Alternatively, if any issues are found, they are indicated by the number in the brackets adjacent to the tool name.

    Observe that a blue check mark appears on the top-left corner of the Validate icon. This indicates that the tool found no issues with the geometry model.


    Figure 22.
  2. Press Esc or right-click in the modeling window and select Exit from the context menu to exit the tool.
  3. Save the database.

Set Up the Problem

In this step, you will set the general simulation parameters such as equation, solver settings, etc. Then, you will assign the surface boundary conditions and material properties to the fluid domain.

Set Up the Simulation Parameters and Solver Settings

  1. From the Flow ribbon, click the Physics tool.


    Figure 23.
    The Setup dialog opens.
  2. Click the Time setting and ensure that Steady is selected.


    Figure 24.
  3. Click the Flow setting.
  4. Check that the flow type is set to Turbulent.
  5. Select Spalart-Allmaras as the Turbulence model.
    The robustness and accuracy of the Spalart Allmaras turbulence model makes it an excellent choice for simulation of steady state flows.


    Figure 25.
  6. Click the Solver controls setting and verify that the parameters are set as shown in the figure below.


    Figure 26.
  7. Exit the Setup dialog.

Assign Material Properties

  1. From the Flow ribbon, click the Material tool.


    Figure 27.
  2. From the modeling window, click anywhere on the manifold.
    The entire manifold geometry is highlighted and a Material microdialog appears.


    Figure 28.
  3. Click the drop-down menu and select Water from the list of materials.
  4. On the guide bar, click to execute the command.
    The changes made in the tool are not effective until they are executed by clicking the icon.
    Once the command is executed, the color of the geometry changes to indicate the material assigned to the volume. In this case, there is only one volume in the geometry so there is a single color. Alternatively, if there are multiple volumes with different materials assigned, the model will be displayed accordingly with distinct colors for each material assigned.


    Figure 29.
  5. On the guide bar, click to exit the tool.

Assign the Flow Boundary Conditions

The current model has one inlet, three outlets, and walls for the rest of the surfaces. When a geometry model is imported into HyperWorks CFD, all the surfaces are placed in the Default Wall (i.e. Type = auto_wall). As you start assigning the surface boundary conditions, those surfaces are moved into a new boundary condition group. All the surface boundary condition tools are placed under the Boundaries sub-section of the Flow ribbon.

  1. From the Flow ribbon, Profiled tool group, click the Profiled Inlet tool.


    Figure 30.
  2. In the modeling window, click the surface of the inlet.


    Figure 31.
    Observe that a new group named "Inlet" is created under the Boundaries list in the top-left corner of the modeling window. Once the current command is executed, the highlighted surface will be moved into the Inlet group.
  3. In the dialog that appears, enter a value of 2.0 m/sec for Average velocity.


    Figure 32.
  4. On the guide bar, click to execute the command.
    The color of the inlet surface in the modeling window is updated.
    Note: The color assigned to the surfaces is random. Therefore, the color of the surfaces shown in the images below might be different from what you see on your screen.


    Figure 33.
  5. Click the Outlet tool.


    Figure 34.
  6. Click the three outlet surfaces shown in the figure below.


    Figure 35.
  7. Leave the default options in the dialog unchanged then click on the guide bar to execute the command.
    The color of the outlet surfaces change and the list of boundaries on the left are updated. The number of surfaces under each group are shown in the brackets.


    Figure 36.
    Note:
    • To update the color of any group, click on the colored-square on the left of the group name and select the color of your choice from the palette.
    • To update the name of any group, right-click on the group name and select Rename from the context menu.
  8. On the guide bar, click to exit the tool.
  9. Save the model.

Define Mesh Controls

Now that you have assigned the material properties and boundary conditions, you will define the meshing parameters for the model and then generate the mesh.

Define the Surface Mesh Controls

  1. From the Mesh ribbon, click the Surface tool.


    Figure 37.
  2. Right-click in the modeling window and go to Select > All.


    Figure 38.
    All the surfaces in the model are highlighted and a dialog for surface mesh parameters appears.
  3. Enter 0.003 for the Average element size.


    Figure 39.
  4. Leave the default values for the remaining parameters unchanged then click on the guide bar to execute the command.

Define the Boundary Layer Mesh Parameters

  1. From the Mesh ribbon, click the Boundary Layer tool.


    Figure 40.
  2. Right-click in the modeling window and go to Select > Advanced Select > By Boundaries > Default Wall.


    Figure 41.
    All the wall surfaces are highlighted and a dialog for boundary layer parameters appears.
  3. Enter the values in the dialog as shown in the figure below.


    Figure 42.
  4. On the guide bar, click to execute the command.

Generate the Mesh

  1. From the Mesh ribbon, click the Batch tool.


    Figure 43.
  2. In the Meshing Operations dialog, enter an Average element size of 0.005.


    Figure 44.
  3. Click Mesh.
    Once the meshing process has started, the Run Status dialog appears. To view the status of the meshing process, right-click on the process row and select View log file.
    Once the meshing is done, the run status is updated accordingly, and you are automatically moved to the Solution ribbon.


    Figure 45.

Run AcuSolve

  1. From the Solution ribbon, click the Run tool.


    Figure 46.
  2. In the Launch AcuSolve dialog, verify that the Problem directory and AcuRun path are pointing to the correct location.
  3. Set the Parallel processing option to Intel MPI.
  4. Optional: Set the number of processors to 4 or 8 based on availability.
  5. Deactivate the Automatically define pressure reference option.
  6. Expand the Default initial conditions menu.
  7. Deactivate the Pre-compute flow option and enter 2.0 for x-velocity.
  8. Deactivate the Pre-compute turbulence flow option and enter 1e-5 for Eddy viscosity.
  9. Leave the remaining options as default and click Run to launch AcuSolve.


    Figure 47.
    The Run Status dialog opens again and the AcuSolve run appears on the list.
  10. Right-click on the AcuSolve run and select View log file.

    A summary of the run printed in the dialog indicates that AcuSolve has finished running the simulation. Once the solution is converged, the Status will be updated accordingly.



    Figure 48.
  11. In the Run Status dialog, right-click on AcuSolve and select Plot time history from the context menu.
  12. In the Plot Utility dialog, double-click on the Residual Ratio row to open the plot of residual ratios.


    Figure 49.

    The above plot shows the residuals of the equations as the solution progresses through each time step. You can see the residuals dropping smoothly. Once the pressure and velocity residual ratios reach a value less than the specified convergence tolerance (0.001), the solution is considered to be converged. By default, the eddy viscosity convergence tolerance is set to a magnitude of one order higher than the specified convergence tolerance (0.01).

Post-Process the Results with HyperView

This part of the tutorial shows you how to work with steady state analysis data in HyperView once the solution has converged.

Open HyperView and Load the Model and Results

  1. Start HyperView from the Windows Start menu by clicking Start > All Programs > Altair <version> > HyperView.
    Once the HyperView window is loaded, the Load model and results panel should be open by default. If you do not see the panel, click File > Open > Model.
  2. In the Load model and results panel, click next to Load model.
  3. In the Load Model File dialog, navigate to your working directory and select the AcuSolve .Log file for the solution run that you want to post-process. In this example, the file to be selected is Manifold.1.Log.
  4. Click Open.
  5. Click Apply in the panel area to load the model and results.
    The model is colored by geometry after loading.

Apply Pressure Contours on the Boundary Surfaces

  1. Click on the Results toolbar to open the Contour panel.
  2. In the Contour panel, select Pressure (s) as the Result type.
  3. Click Apply.


    Figure 50.
  4. In the panel area, under the Display tab, turn off the Discrete color option.


    Figure 51.
  5. Click the Legend tab then click Edit Legend. In the dialog, change the Numeric format to Fixed then click OK.
    The pressure contour should be displayed as shown in the figure below.


    Figure 52.

Save Plots as Image Files

  1. On the Image Capture toolbar toggle the / icons so that it shows the icon to save to file.
  2. Click the icon on the Image Capture toolbar.
  3. Provide a name for the image in the dialog and click Save.
    If you want to use the image in a presentation you can copy them to the clipboard by toggling the Save Image to File/Clipboard icon to instead of . Then paste the image in your presentation.

Create Pressure and Velocity Contours on a Cut Plane

  1. To create a new cut plane, right-click in the Results Browser and select Create > Section Cut > Planar from the context menu.
    A new entity, Section 1, is created in the Results Browser.
  2. Right-click Section 1 and select Edit from the context menu.
  3. In the Section Cut panel verify that Define plane is set to Y Axis.
  4. Under the Display options, activate the Cross section check box.
  5. Verify that the Clip elements check box is activated.
  6. For the Base coordinates, enter a value of -0.015 for the Y-coordinate and press Enter.


    Figure 53.
  7. Click on Gridline in the panel area.
  8. In the dialog, uncheck the Show option under Gridline then click OK.


    Figure 54.
  9. Click on the Results toolbar to open the Contour panel.
  10. In the Contour panel select Velocity as the Result type.
  11. Click Apply.


    Figure 55.

Create a Clipping Plane

The section cut plane can be used as a clipping plane as well. In this step you will create a clipping plane.
  1. Right-click Section 1 under Section Cuts in the Results Browser and select Edit from the context menu.
  2. In the Section Cut panel change the selection under Display options from Cross section to Clipping plane.


    Figure 56.
  3. Click Reverse to toggle the clipping direction to your choosing.


    Figure 57.

Create Velocity Vectors

  1. In the Section Cut panel under Display options, set the selection back to Cross section.
  2. Click the icon on the Results toolbar.
  3. On the Vector panel, make sure that the Result type is set to Velocity (v).
  4. Set the Selection mode to Sections using from the drop-down menu.
  5. Click the Sections collector to open the Extended Entity Selection dialog.
  6. Click Displayed.


    Figure 58.
  7. Select the Z+X Resultant option.


    Figure 59.
  8. Click Apply.
  9. Click the Display tab and set the options as shown in the figure below.


    Figure 60.
  10. Click the Section tab and activate the Projected and Evenly distributed check boxes.
  11. Set the Number of rows and columns to 20 and 50 respectively then click Apply.


    Figure 61.
    The vector plot should be displayed as shown in the figure below.


    Figure 62.

Display Streamlines

  1. In the Results Browser, expand the Section Cuts folder.
  2. Click the icon next to Section 1 to turn off its display.
  3. In the Results Browser, turn off the display for all components except Inlet and Outlet.


    Figure 63.
  4. Click the icon on the Results toolbar to open the Streamlines panel.
  5. Click Add to add a new set of streamlines.
  6. Set the Rake type to Line, if not already selected.
  7. Click the icon.
    The Reference point dialog opens.
  8. Enter the reference points as shown in the figure below.


    Figure 64.
  9. In the panel area, set the Integration mode to Downstream and the Number of seeds to 20.
  10. Make sure that the Source is set to Velocity.
  11. Click Create Streamlines.
  12. Enter the Streamline Size as 3 and press Enter .


    Figure 65.


    Figure 66.

Summary

In this tutorial, you worked through a basic workflow to carry out a CFD simulation and post-processed the results using HyperWorks products, namely HyperWorks CFD and HyperView. You started by importing and meshing the model in HyperWorks CFD. You also set up the model and launchedAcuSolve directly from within HyperWorks CFD. Upon completion of the solution by AcuSolve, you used HyperView to post-process the results. You learned how to create contours on the boundary surfaces and the section cuts, velocity vectors, and streamlines.