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.

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

pfsi_energy_harvester_model_intro
Figure 1. Schematic of the Problem

pfsi_beam_with_various_layers
Figure 2. Various Layers of Beam

The AcuSolve fluid model (slab_dcfsi.inp) and the OptiStruct structural beam model (Slab.fem) are located in the fsi_models.zip file. Refer to Access the Model Files.

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. Refer to Access the Model Files.
  5. Click Open.
  6. Click Import, then click Close to close the Import tab.

Set Up the Model

Create Contact Surface

  1. In the Model Browser, right-click and select Create > Set Segment from the context menu.
    A default contact surface template displays in the Entity Editor.
  2. For Name, enter FSI_Interaction_Surf.
  3. Click Color and select a color from the color palette.
  4. For Elements, click 0 elements > elements and pick all the faces of the beam.

    os_1600_surf
    Figure 3. All sides of the beam except in the front
  5. Click add to add the faces to the contact surface.
  6. Click return to exit from this panel.

Define Nonlinear 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 NLPARM_Card.
  3. Click Color and select a color from the color palette.
  4. For Card Image, select NLPARM.
  5. Input the values, as shown in Figure 4.
    See NLPARM Bulk Data Entry for more information.

    os_1600_nlparm
    Figure 4.

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_Card.
  3. For Card Image, select TSTEP.
  4. For TSTEP NUM, enter 1.
  5. Click table_pencil and input the values, as shown in Figure 5.
    See NLPARM Bulk Data Entry for more information.

    os_1600_tstep
    Figure 5.
  6. Click Close to finish.

Define Incremental Result Output for Nonlinear Analysis

  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 NLOUT101.
  3. Click Color and select a color from the color palette.
  4. For Card Image, select NLOUT.
  5. Input the values, as shown in Figure 6.
    See NLPARM Bulk Data Entry for more information.

    os_1600_nlout
    Figure 6.

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.
  5. 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.
  4. 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 Nonlinear transient.
  5. Input/Select the Load Collector.

    os_1600_load_collector
    Figure 8.
  6. Reference the NLOUT Bulk Data Entry as a SUBCASE_UNSUPPORTED entry as:

    os_1600_subcase_unsupported
    Figure 9.

Submit the Job

  1. From the Analysis page, click the OptiStruct panel.

    OS_1000_13_17
    Figure 10. Accessing the OptiStruct Panel
  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.

Initiate a Run

  1. Launch the Compute Console (ACC) and select the Slab.fem file.
  2. Click Run.

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.

    os_1600_acusolve_command
    Figure 12.
  3. Open the AcuSolve Cmd Prompt application and enter the command: acuRun-pb slab_dcfsi -np 8.


    Figure 13.
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 14.