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UserFunction Object




User-defined function. Used as a parameter for GetCustomIntegral.


UserFunction object is the interface for calculation the custom user-defined function. In QuickField 6.2 user-defined function is used as integrand for calculation custom integrals with methods GetCustomIntegral and GetCustomIntegralTotal of the Result object.

QuickField has no implemented object with this interface. QuickField user should implement this interface in his/her program.

UserFunction interface has the only method:
   Sub GetValue (point, bodyLabel, resValue)
with two input parameters point and bodyLabel an one output parameter resValue. All three parameter have to be declared with the ByVal keyword.

The calculated value resValue has the Quantity type, which is a container for physical quantities of different types (scalar, vector, complex etc.).

point as FieldPoint

Coordinates of the point where the custom function should be calculated and local field values there. Parameter is an object of the FieldPoint type or derived types (FieldPointES, FieldPointCF, FieldPointTE, FieldPointTV, FieldPointHE, FieldPointSA, FieldPointEC) depending on the analysis type.

bodyLabel as String

This parameter contains the label of the current block, through which the integration contour goes through

Calculated value resVal of the Quantity type

Calculated value of the custom function should be put into the object of Quantity type, which includes information about the type and value. GetValue function should not create or delete the Quantity object. Its creation and removal should be performed in the calling program code.

The following example showcases UserFunction, which implements the core loss calculation in the ferromagnetic material using Steinmetz equation

           p = kloss·Bmα·fβ,

where p - specific volume losses, Bm - flux density magnitude, f - frequency, kloss, α, β - constants related to the material properties and magnetic field change mode.

1. Visual Basic for Application (VBA)

First example is implemented in Visual Basic for Appliation (VBA) within MS Excel environment. This code should be placed into the separate Class Module, which is in our example named LossFunction. The class module should have the attribute Instancing = 2 (PublicNotCreatable) in the module property dialogue.

Option Explicit

Implements QuickField.UserFunction

Public pbm As QuickField.Application

Public Sub UserFunction_GetValue(ByVal Point As QuickField.FieldPoint, ByVal bodyLabel As String, ByVal resVal As QuickField.Quantity)
   ' derive the Point parameter from the base type FieldPoint to the derived type FieldPointHE,
   ' which corresponds to the problem analysis type
   Dim pointHE As QuickField.FieldPointHE
   Set pointHE = Point
   ' Steinmetz loss equation coefficients
   Const lossFactor As Double = 0.12345
   Const alpha As Double = 2.05
   Const beta As Double = 1.3
   Const frequency As Double = 50
   Dim B As Double
   Dim lossDensity As Double
   ' to calculate the custom function we need the flux density magnitude:
   B = pointHE.FluxDensity.Magnitude.R
   lossDensity = lossFactor * WorksheetFunction.Power(frequency, beta) * WorksheetFunction.Power(B, alpha)
   ' store the calculated value to return the result
   resVal.SetAsScalar lossDensity
End Sub

Following fragment calculates the custom user-defined volume integral using the redefined UserFunction:

   Dim flag As Long                       ' flag is necessary to call the integrand function
   Dim q As QuickField.Quantity   ' integral calculation result
   Dim res As Double '
   flag = 0
   Set myFunc = New VBAProject.LossFunction   ' LossFunction here is the name of the Class Module, where our interface UserFunction is defined
   Set q = res.GetCustomIntegral(myFunc, qfOverVolume, cnt)    ' the call of the method for calculation of the user integral over the volume inside the closed contour

2. C# language

Second variant is written in C#. Simple implementation of the UserFunction interface may look like:

class CoreLoss : QuickField.UserFunction
   public void GetValue(QuickField.FieldPoint point, string blockLabel, ref QuickField.Quantity res)
     const double lossFactor = 0.12345;
     const double alpha = 2.05;
     const double beta = 1.3;
     const double frequency = 50;
     var pointHE = point as FieldPointHE;
     double B = pointHE.FluxDensity.Magnitude.R;
     double val = lossFactor * Math.Pow(frequency, beta) * Math.Pow(B, alpha);

To calculate the custom integral ober the volume, which is limited by the closed contour, it is required to create the new instance of the class, which implements the interface QuickField.UserFunction, and pass it as a parameter at the call of GetCustomIntegral method of the QuickField.Result class:

  var myUserFunc = new CoreLoss(pbm);
  double custom = res.GetCustomIntegral(myUserFunc, qfOverVolume, cont).Abs;