OS-T: 1380 Computation of Equivalent Radiated Power

Computation of the equivalent radiated power (ERP) is a simplified method to gain information about maximum dynamic radiation of panels for excitations in frequency response analysis. This tutorial demonstrates how to set up the computation request of ERP on an existing frequency response analysis.

The model is a front cover of catalytic converter in a car exhaust system, as shown in Figure 1. The frequency analysis setup is already made for this model where the cover is constrained at two ends, and the excitation loading is applied at the center of the cover. The loading frequency is defined by FREQ1 card; from 120.0 to 400.0 Hz with an interval of 1.0. You need to define ERP panels (ERPPNL) and ERP output request.

rd2130_model
Figure 1. Model Review

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.

Open the Model

  1. Click File > Open > Model.
  2. Select the cover.fem file you saved to your working directory from the optistruct.zip file. Refer to Access the Model Files.
  3. Click Open.
    The cover.fem database is loaded into the current HyperMesh session, replacing any existing data.

Set Up the Model

Create ERPPNL Set

ERPPNL is defined as a set of elements. An element set ERP_elem has been predefined in the model. It can be reviewed in HyperMesh.
  1. Go to the entity sets panel on Analysis page.
  2. Click review and select ERP_elem.
    The elements should be highlighted on the screen.
  3. Click return to go back to the main menu.
  4. In the Model Browser, right-click and select Create > Set.
    A default set template is now displayed in the Entity Editor below the Model Browser.
  5. For Name, enter ERPPNL.
  6. For Card Image, select ERPPNL and click Yes to confirm.
  7. For Entity IDs, click Unspecified > Sets.
  8. In the Select Sets dialog. select the ERP_elem set and click OK.

Define ERP Output Request

You will request the ERP output in control cards panel.

  1. From the Analysis page, click control cards.
  2. Go to the GLOBAL_OUTPUT_REQUEST panel.
  3. Check the box in front of ERP and enter 2 in the ERP_NUM field.
  4. Set FORMATs, GRIDs, and OPTIONs for the ERP output, as shown below.

    rd2130_erp_output
    Figure 2. ERP output

    The grid contribution of each grid in addition to the ERP results for the panel is output to an .h3d file. ERP panel results are output to punch format.

  5. Click return twice to return to the Analysis page.

Submit the Job

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

    OS_1000_13_17
    Figure 3. Accessing the OptiStruct Panel
  2. Click save as.
  3. In the Save As dialog, specify location to write the OptiStruct model file and enter cover_ERP 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 cover_ERP.fem was written. The cover_ERP.out file is a good place to look for error messages that could help debug the input deck if any errors are present.

Post-process the ERP Results in HyperView

  1. From the OptiStruct panel, click HyperView.
    HyperView is launched and the results are loaded. A message window appears to inform of the successful model and result files loading into HyperView.
  2. Select Subcase 1 (frf) as the current load case in the Results browser.
  3. Select the last load step where frequency is 50.0Hz.
  4. On the Results toolbar, click resultsContour-16 to open the Contour panel.
  5. Select Equivalent Radiated Power (ERP_elem) as Result type and then select Panel.
  6. Click Apply.
    ERP results on panel should be plotted.
  7. Select Equivalent Radiated Power (ERP_elem) as Result type and then select Grid Contributions.
  8. Click Apply.
    The contour of grid contributions to ERP should be loaded.

    rd2130_erp_results
    Figure 4. ERP Results in HyperView

Post-process the ERP Results in HyperGraph

  1. Launch HyperGraph.
  2. Click Build Plots.
  3. Load cover_ERP.pch file in Data file.
  4. Check that X Type is set to Frequency [Hz].
  5. Check that Y Type is set to Subcase 1 ERP.
  6. Select Frf ERP_elem in Y Request and ERP in Y Component field.
  7. Click Apply.
    The plot of ERP panel results versus loading frequency should be loaded, as shown below. The ERP (dB) results are available, as well.

    rd2130_hg_results
    Figure 5. ERP Results in HyperGraph