Magnetic forces computation and export in Flux

Introduction

This section presents the steps to follow in Flux to compute and export forces harmonics. The steps are as following:
  • Create the computation support
  • Compute the forces and forces harmonics
  • Visualize the forces
  • Export the forces

Flux project

The Flux project can be in 2D or 3D in transient magnetic application (for NVH analysis).

Import/Export context

The Import/Export context is dedicated to all couplings with other software, including the coupling with OptiStruct.

To enter in the Import/Export context respectively after and before solving:

Data exchange > Open data import/export context

Parameter/Quantity > Open data import/export context

Mechanical context

When entering in the Import/Export context, user has to choose the dedicated context: Mechanical or thermal or generic.

Here the mechanical context is chosen:

Creation of the support

In this part, the approach to create the support defined by importing a mesh is presented. The imported mesh corresponds to the mesh exported before which will be used for the forces computation in Flux and for the vibratory analysis in OptiStruct.

There is also in Flux a support defined by Flux entities, but this requires an interpolation step when importing forces into HyperMesh (for more information, please refer to the online help).

  1. Open the box to create the support:Data support > New

  2. Choose the data support Support defined by importing a mesh
  3. Choose the type of file to import OptiStruct .fem file
  4. Select the file to import
  5. Select the coordinate system.
    Note: Depending on the length units, user may have to create and select a new global coordinate system with the right units.
  6. Select the mechanical set.

    It is especially useful if the support must follow a moving mechanical set.

  7. Click on OK to create the support.
    The data support is created:

Compute the forces

The steps to compute the forces harmonics are described below.
  1. Open the box to create the forces data collection:Data collection > Forces data collection > New

  2. Choose the Forces data collection Forces collection dedicated to rotating machine with mesh import
  3. Choose the data support created before
  4. Choose the automatic computation of the radius in the airgap.

    The forces will be computed on this radius before being projected on the imported mesh.

    A value can be setted by the user. In this case, it is advised to choose its value on ¼ distance of the airgap thickness, stator/rotor side, according to where the imported support is.
  5. Choose the collection interval:
    • Collect for all steps of the scenario
    • Or collect for a specified interval. This choice allows reducing computation time
  6. Click on OK to create the data collection
    The data collection is created:

  7. Open the box to create a derived data collection:Data collection > Derived data collection > New

  8. Select the FFT of a time collection
  9. Select the data collection DATACOLLECTION_1 created before
  10. Select the time interval for the FFT, corresponding to one period.
  11. Select Automatic duplication of forces for rotating machines
  12. Click on OK to create the derived data collection.
    The derived data collection is created:

  13. Evaluate the forces and forces harmonics values:

    Data collection > collect data

    Note: if the project is not solved, this command will not be available. In fact, the collection is done during the solving (it allows reducing computation time).

Visualize the forces

The steps to visualize the forces or forces harmonics arrows are described below.
  1. Open the box to visualize the forces:Data visualizer > Forces visualizer > New

  2. User can choose display forces or display harmonic forces and user has to select for collections dedicated to rotating machines
  3. Choose the data collection to visualize (forces or forces harmonics)
  4. It is possible to visualize the following components of the forces vectors:
    • Resulting
    • Normal
    • Tangent
  5. It is possible to visualize:
    • Forces at nodes
    • Global forces. It corresponds to the resulting forces on one geometrical part (one stator teeth for example)
  6. If user has selected the forces harmonics visualization, the rank of the harmonic to visualize must be chosen.
  7. Click on OK to create the data visualizer entity and visualize the forces.
    The data visualizer is created and the forces arrows displayed:

  8. When the forces arrows are visible, it is possible to plot an evolutive curve:
    • Forces harmonics module depending on the frequency:
      • Make the harmonics arrows visible
      • Open the FFT data evolution curve:

        Data visualizer > Results and curves on one point > FFT data evolution curve



      • Choose the node in the graphic (FFT type data point)
      • Select the number of harmonics to display

    • Forces module depending on the time:
      • Make the forces arrows visible
      • Open the Standard data evolution curve

        Data visualizer > Results and curves on one point > Standard data evolution curve



      • Choose the node in the graphic (Standard type data point)
      • Define the time/position interval

Export the forces

The steps to export the forces harmonics are described below.
  1. Open the box to export the forces:

    Data export > Data export to OptiStruct > New



  2. Select the Forces (frequency-evolution) to export
  3. Select the derived data collection DATACOLLECTION_2 to export
  4. Select harmonics to export (the selection may be done by choosing either all, an interval or a list of harmonics).
  5. Choose the file name
  6. Click on OK to export the forces harmonics and create the data export entity:

    The data export entity is created and the forces harmonics exported in a .fem file: