Direct method for volume forces (dFLapV)


This chapter discusses the use of the Direct method for volume forces (dFLapV) to create force collections in the Import / Export data context: this kind of collection allows to compute Laplace forces on a volume mesh with the forces density dFLapV.

The following topics are covered in this page:
  • Description of the approach
  • Creation of this force collection
  • Limitations
  • Example

Description of the approach

This approach computes a force density on a volume support (Flux mesh or imported mesh) defined with a data support as shown in Figure 1 .

Figure 1. Support defined from the Flux mesh on the secondary coils of a power transformer.

Laplace forces density are created in a region by the interaction of the current density J with the magnetic flux density B such as : dF = J x B . The volume regions with a non-zero current density and magnetic flux density are the following ones:

  • Solid conductors
  • Coil conductors
The Laplace forces density dFLapV is directly computed on the support and then is integrated with several methods to get the most adapted distribution for mechanics-coupled simulations.

Creation of this collection

This method to compute forces (and so this kind of collection) is available in all Flux modules (2D, 3D and Skew) for all the magnetic applications. This collection can be created as follows:
  • In the data tree, select the menu Forces data collection
  • In the dedicated GUI for Forces data collection, choose Direct method for volume forces (dFLapV)
  • Choose a data support to collect the data
  • Choose the collection interval:
    • Collect for all the steps of the scenario
    • Collect only for the current step
    • Collect for a specified interval
  • Click OK
  • Right click on the forces data collection just created in the data tree and run the command Collect data
Note: For AC Steady State applications, the user must also choose the type of values to collect: continuous, instantaneous (the phase value is asked) or pulsating values.
Note: In advanced mode, more integration options are available, see this page for more details.
Once the collection is created and the data collected, forces (either at nodes or global on the support) can be visualized with the Data visualizers and / or exported to OptiStruct with the Data export function.


In this example, the aim is to compute the forces in the winding of a power transformer shown in Figure 1.

We define a support to collect the data: it comes from the Flux mesh and is the same as the one described in Figure 1; it is based on the volumes which are described as coil conductor regions representing the secondary winding of the power transformer. As these parts are subjected to important forces they may vibrate and produce an annoying sound.

Once the collection is correctly defined, the data must be collected by right click and Collect data on the forces data collection; now forces can be visualized with the Data visualizers as shown in the figure below:

Figure 2. Distribution of nodal force densities in the secondary coil of a power transformer.

These forces can also be exported to OptiStruct with the Data export in order to proceed to a NVH analysis of the winding.