OS-T: 1600 Fluid-Structure Interaction Analysis of Piezoelectric Harvester Assembly

The purpose of this tutorial is to demonstrate how to carry out Fluid-Structure Interaction analysis that is, with OptiStruct nonlinear transient analysis coupling within AcuSolve fluid dynamic analysis.

Before you begin, copy the file(s) used in this tutorial to your working directory.
In this tutorial, you will explore the possibility of using piezoelectric based fluid flow energy harvesters. These harvesters are self-excited and self-sustained in the sense that they can be used in steady uniform flows. The configuration consists of a piezoelectric cantilever beam with a cylindrical tip body (which is the structure model) which promotes sustainable, aero-elastic structural vibrations induced by vortex shedding and galloping. The structural and aerodynamic properties of the harvester alter the vibration amplitude and frequency of the piezoelectric beam and the fluid flow. As you may know, the Piezoelectric energy harvesting using fluid flow involves the mutual interaction of three distinct dynamic systems, namely the fluid, the structure and the associated electrical circuit.
Note: This tutorial is limited to study only fluid and the structure domain.
Figure 1. Schematic of the Problem

pfsi_energy_harvester_model_intro
Figure 2 illustrates the fluid structural model used for this tutorial: the dimensions of the beam are shown in Figure 1 and Figure 2.
Figure 2. Various Layers of Beam

pfsi_beam_with_various_layers

Launch HyperMesh and Set the OptiStruct User Profile

  1. Launch HyperMesh.
    The User Profile dialog opens.
  2. Select OptiStruct and click OK.
    This loads the user profile. It includes the appropriate template, macro menu, and import reader, paring down the functionality of HyperMesh to what is relevant for generating models for OptiStruct.

Import the Model

  1. Click File > Import > Solver Deck.
    An Import tab is added to your tab menu.
  2. For the File type, select OptiStruct.
  3. Select the Files icon files_panel.
    A Select OptiStruct file browser opens.
  4. Select the Slab.fem file you saved to your working directory.
  5. Click Open.
  6. Click Import, then click Close to close the Import tab.

Set Up the Model

Create Set Segment

  1. In the Model Browser, right-click and select Create > Set Segment from the context menu.
  2. For Name, enter FSI_Interaction_Surf.
  3. Click Color and select a color from the color palette.
  4. For Card Image, select SURF from the drop-down menu.
  5. For Elements, click 0 elements > elements and pick all the faces of the beam.
    Figure 3. All sides of the beam except in the front

    os_1600_surf
  6. Click add to add the faces to the set segments.
  7. Click return to exit from this panel.

Define Nonlinear Parameters

  1. In the Model Browser, right-click and select Create > Load Step Inputs.
  2. For Name, enter NLPARM.
  3. For Config type, select Nonlinear Parameters from the drop-down menu.
  4. For Type, NLPARM is the default.
  5. Input the values, as shown in Figure 4.
    See NLPARM Bulk Data Entry for more information.
    Figure 4.

    os_1600_nlparm

Define Transient Time Step Parameters

  1. In the Model Browser, right-click and select Create > Load Collector.
    A default load collector template displays in the Entity Editor.
  2. For Name, enter TSTEP.
  3. For Card Image, select TSTEP.
  4. For TSTEP NUM, enter 1.
  5. Input the values, as shown in Figure 5.
    See NLPARM Bulk Data Entry for more information.
    Figure 5.

    os_1600_tstep

Define Incremental Result Output for Nonlinear Analysis

  1. In the Model Browser, right-click and select Create > Load Step Inputs.
  2. For Name, enter NLOUT101.
  3. For Config type, select Output Parameters from the drop-down menu.
  4. For Type, NLOUT is the default.
  5. Input the values, as shown in Figure 6.
    See NLPARM Bulk Data Entry for more information.
    Figure 6.

    os_1600_nlout

Define Fluid-Structure Interaction Parameters

  1. In the Model Browser, right-click and select Create > Load Collector.
    A default load collector template displays in the Entity Editor.
  2. For Name, enter FSI100.
  3. Click Color and select a color from the color palette.
  4. For Card Image, select FSI from the drop-down menu.
  5. Under ELSET, for SURFID, select FSI_Interaction_Surf.
  6. Input the values, as shown in Figure 7.
    See NLPARM Bulk Data Entry for more information.
    Figure 7.


Define Output Control Parameters

  1. From the Analysis page, select control cards.
  2. Click GLOBAL_OUTPUT_REQUEST.
  3. For DISPLACEMENT, ELFORCE, OLOAD, STRESS, and STRAIN, set Option to Yes and click return.
  4. Click PARAM.
  5. Select LGDISP, and for LGDISP_V1 enter 1.
  6. Click return twice to go to the main menu.

Create Nonlinear Transient Analysis Subcase

  1. In the Model Browser, right-click and select Create > Load Step from the context menu.
  2. For Name, enter FSI.
  3. Click Color and select a color from the color palette.
  4. For Analysis type, select Non-linear transient.
  5. Input/Select the Load Collector.
    Figure 8.

    os_1600_load_collector

Submit the Job

  1. From the Analysis page, click the OptiStruct panel.
    Figure 9. Accessing the OptiStruct Panel

    OS_1000_13_17
  2. Click save as.
  3. In the Save As dialog, specify location to write the OptiStruct model file and enter Slab for filename.
    For OptiStruct input decks, .fem is the recommended extension.
  4. Click Save.
    The input file field displays the filename and location specified in the Save As dialog.
  5. Set the export options toggle to all.
  6. Set the run options toggle to analysis.
  7. Set the memory options toggle to memory default.
  8. Click OptiStruct to launch the OptiStruct job.
If the job is successful, new results files should be in the directory where the Slab.fem was written. The Slab.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Submit the AcuSolve Job

  1. Open the AcuSolve input file (slab_dcfsi.inp) in a text editor.
  2. Change the socket_host parameter in the EXTERNAL_CODE block to your machines hostname and save the file.
    Figure 10.

    os_1600_acusolve_command
  3. Open the AcuSolve Cmd Prompt application.
  4. Enter the command: acuRun-pb slab_dcfsi -np 8.
    Figure 11.


If the job is successful, you will see new results files in the directory where HyperMeshwas invoked. The Slab.out file is where you will find error messages that will help you debug your input deck, if any errors are present.
The default files that will be written to your directory are:
cci.txt
Contains information pertaining to model progression. Logs regarding connection establishment, initial external code handshake and subsequent time step data in conjunction with exchange/stagger.
Slab.html
HTML report of the analysis, giving a summary of the problem formulation and the analysis results.
Slab.out
ASCII based output file of the model check run before the simulation begins and gives some basic information on the results of the run.
Slab.stat
Summary of analysis process, providing CPU information for each step during the process.
Slab.h3d
HyperView compressed binary results file.

View the Results

Using HyperView, plot the Displacement contour at 1.0 s.
Figure 12.