Phase Function Renormalization Tolerance

Phase Funtion Renormalization Tolerance = <float>

Description / Usage

This parameter provides a means for controlling how often renormalization (redistancing) operations are performed on the phase function fields as they evolve by fixing the size of the deviation allowed between the average absolute magnitude of the phase function gradient near each respecitve interface and unity, the theoretical value observed for a pure distance function.

<float>

Value of the tolerance, the allowable deviation.

The range of this parameter is any positive real number, however, it is rare to use values smaller than 0.1 or larger than 5.0. The value of the tolerance defaults to 0.5 if this card is not specified. Note that a global parameter value is applied to all phase function fields in the problem. Currently, there is no provision for each phase function field to have a unique value for this parameter.

This parameter is exactly analogous to the similarly named parameter used in standard level set interface tracking.

Examples

This is a sample renormalization card:

Phase Function Renormalization Tolerance = 0.25

Technical Discussion

The reader is referred to the Technical Discussion associated with Level Set Renormalization Tolerance card as it is virtually identical to the operation of it in the current context. The only thing to note is that each phase function is evaluted separately against this tolerance and each function is renormalized independently if the tolerance is exceeded. That is, exceeding the tolerance by one phase function field only triggers renormalization for that field. The other phase function fields are left unaltered.

FAQs

What is a proper value for this parameter? Values on the order of unity should work well. Renormalization based on gradient can be disabled completely by choosing a very large value for this parameter. Conversely, a very small value will always result in a renormalization step.

Is it possible to renormalize too often? Yes. Renormalization is an extraphysical procedure designed solely to improve the numerical performance of the interface tracker. As such, it can add or subtract volume to or from the phases represented by the interface contour. Renormalizing too often, therefore, can result in errors being introduced. The renormalization procedure, Huygens_Constrained, attempts to mitigate this effect.