Scattering off Multiple Objects (dielecPlusMetalObjs.sdf)

Keywords:

electromagnetics, pulse, dielectric

Problem Description

The Scattering off Multiple Objects simulation illustrates the ability to define different materials with different dielectric properties (perfect electric conductor, sapphire, alumina) and have an electromagnetic pulse reflect off of both a complex metal surface and dielectric medium. It also illustrates a wave launcher to be used with different dielectric materials. This example can also be modified to calculate Radar Cross Sections.

This simulation can be performed with a VSimEM, VSimVE or VSimPD license.

Opening the Simulation

The Scattering off Multiple Objects example is accessed from within VSimComposer by the following actions:

  • Select the New → From Example… menu item in the File menu.

  • In the resulting Examples window expand the VSim for Electromagnetics option.

  • Expand the Scattering option.

  • Select “Scattering off Multiple Objects” and press the Choose button.

  • In the resulting dialog, create a New Folder if desired, and press the Save button to create a copy of this example.

All of the properties and values that create the simulation are now available in the Setup Window as shown in Fig. 325. You can expand the tree elements and navigate through the various properties, making any changes you desire. The right pane shows a 3D view of the geometry, if any, as well as the grid, if actively shown. To show or hide the grid, expand the Grid element and select or deselect the box next to Grid.

Setup Window

Fig. 325 Setup Window for the Scattering off Multiple Objects example.

Simulation Properties

This simulation includes just one user defined constant, WAVELENGTH, and just two user defined parameters, FREQUENCY and OMEGA. These three terms will define the incoming wave which is defined in the SpaceTimeFunctions element.

CSG shapes are used to define the geometries of the simulation. A sphere is unioned with a cylinder and given a material of sapphire. The box is an alumina structure and the truncated cone serves as a perfect electric conductor.

Placing all of these shapes and various materials in the same simulation shows how the electromagnetic wave can scatter off of different materials.

Running the Simulation

After performing the above actions, continue as follows:

  • Proceed to the run window by pressing the Run button in the left column of buttons.

  • Check that you are using these run parameters:

    • Time Step: 2.473991708760349e-11

    • Number of Steps: 200

    • Dump Periodicity: 20

    • Dump at Time Zero: Checked

  • Click on the Run button in the upper left corner of the right pane.

You will see the output of the run in the right pane. The run has completed when you see the output, “Engine completed successfully”. This result is shown in Fig. 326.

Run Window

Fig. 326 The Run Window at the end of execution.

Visualizing the Results

After performing the above actions, continue as follows:

  • Proceed to the Visualize Window by pressing the Visualize button in the left column of buttons.

To view the electric field, as well as the geometries as shown in Fig. 327, do the following:

  • Expand Scalar Data

  • Expand E

  • Select E_z

  • Check Clip Plot

  • Set the color limits to -2 and 2

  • Expand Geometries

  • Select poly (AluminaObjectMappedPolyData), poly (PECObject), poly (sapphireObject) and check Clip Plot for each

Initially, no field will be seen, as one is looking at Dump 1 when no fields are yet in the simulation. Move the slider at the bottom of the right pane to see the electric field at different times.

Viz Window

Fig. 327 Visualization of the wave as it hits the objects.

Further Experiments

One idea is to include radar cross section histories at setup time to be able to visualize the far fields.

This example is easily modifiable to include a different geometry and wave form.

Try changing the materials to see how it affects the wave.