STFuncUpdater

STFuncUpdater

Works with VSimBase, VSimEM, VSimPD, VSimPA, and VSimVE licenses.

MultiField updater that performs one of the following operations on a field \(\mathbf{F}\) and an STFunc \(f\):

(8)\[F_j(x,y,z,t+\Delta t) = f(x,y,z,t)\]
(9)\[F_j(x,y,z,t+\Delta t)= F_j(x,y,z,t)+f(x,y,z,t)\]
(10)\[F_j(x,y,z,t+\Delta t)= F_j(x,y,z,t)f(x,y,z,t)\]

For updating a single component of \({\bf F}\), the updater is straightforward; the operation is specified by the operation parameter.

However, for updating multiple components of \({\bf F}\), if different components of \({\bf F}\) are located at different places (e.g., for a Yee electric field, \(E_x\) and \(E_y\) are located at different places within a mesh cell), STFunc is evaluated only once for all components; STFunc is evaluated at the position of the component given by the component parameter of the updater and the field offset of field \({\bf F}\). In this case, the components of \({\bf F}\) that are updated are those given by the parameter writeComponents.

If you want to have \(f\) evaluated at the location of each component then you must use a separate STFuncUpdater definition for each component (or otherwise update all components using FieldMultiUpdater).

STFuncUpdater Parameters

The STFuncUpdater takes the lowerBounds and upperBounds parameters of FieldUpdater, as well as the following parameters:

minDim (optional integer, default = 1)

If the dimension of the simulation is less than minDim, this updater will not be applied.

operation (required string)

One of:

writeFields (required string vector)

A single element, the name of the field to update.

component (optional integer, default = 0)

Component \(j\) of \({\bf F}\) to be updated. However, if writeComponents is not [0], the component, along with the field offset of \({\bf F}\), determines the location in each cell where the function \({\bf f}\) will be evaluated.

writeComponents (optional integer vector, default = [0])

List of components of \({\bf F}\) that will be updated.

Note

The STFunc \(f\) will be evaluated only once per cell for all components, and the location within each cell at which \(f\) is evaluated is determined by the component parameter.

dtCoefficients (optional float vector, default = [1.0 0.0])

Two components [\(c_0\) \(c_1\)]: the function will be multiplied by \(\left(c_0 + c_1 \Delta t\right)\), where \(\Delta t\) is the current time step. If \(c_1\) is not specified it is assumed to be zero.

STFunc (required parameter block)

A parameter block of type STFunc (with any name) must be specified. This describes \(f\).

Example STFuncUpdater block

<FieldUpdater initialPulse>
  kind = STFuncUpdater
  lowerBounds = [NX_BEGIN NY_BEGIN NZ_BEGIN]
  upperBounds = [NX_END NY_END NZ_END]
  operation = set
  writeFields = [elecField]
  component = 2
  <STFunc unimportantName> # a gaussian
    kind = expression
    expression = E_AMP * exp(-0.5 * ( (x-X_INIT)^2 + (y-Y_INIT)^2 \
        + (z-Z_INIT)^2 ) / WIDTH_INIT^2)
  </STFunc>
</FieldUpdater>