Space Field Functions Reference

The following field functions are made available to the simulation when any one of the Space models is used. They include a typical set of base properties.


Cell Aspect Ratio	This field function is used to identify regular polygonal cells from skewed or stretched cells. A value of 1 indicates that the cell is a regular polygon, and a value close to zero would represent a highly stretched cell. This ratio is defined as: $C A R = \frac{N D \times N F \times m a x (V, 0)}{(\sum_{f} \| A_{f} \|) \cdot (\sum_{f} \| \frac{A_{f} \cdot d x}{\| A_{f} \|} \|)}$ where $N D$ is the number of dimensions (three for a 3D mesh and two for a 2D mesh). $N F$ is the number of faces of the cell. $V$ is the volume of the cell. $A_{f}$ is the cell face area vector and $d x$ is the position vector from the face centroid to the cell centroid.
Centroid	Displays the position of the face or cell centroid. At face and cell centroids, the value is the same as the Position field function.
Chevron Quality Indicator	This field function is used to identify chevron cells. These cells are pairs of thin slender cells that share a common face whose angle is such that the line joining the cell centers does not pass through the common face. This indicator function marks chevron cells as 1 and every other cell as 0. A chevron quality norm $c$ , as defined below, is used to determine whether a cell can be classified as a chevron cell or not. The chevron quality norm is computed using a vector $d p$ that is projected from the face center to the line joining the cell centers: $d p = (\frac{A_{f} ∙ d x}{A_{f} ∙ d s}) d s - d x$ $c = 1 - \frac{d p ∙ d p}{m a x (d p ∙ d v)}$ where: $A_{f}$ is the face area vector $d x$ is the vector from the face center to the cell center $d s$ is the vector connecting the two cell centers $d v$ is the vector from the face vertex to the face center. The max function, in evaluating the chevron quality norm, is taken over all the face vertices. The chevron quality norm is: 1 for orthogonal cells in which the line connecting the two cell centers passes through the face centroid 0 when the line passes through an edge of the face negative when the line is outside the face. The chevron quality indicator is marked 1 when the chevron quality norm is negative.
	Two more properties are provided: Chevron Threshold Angle—the maximum angle included by the two cells, beyond which the chevron quality indicator is not computed and is set to 0. You specify this value. Cell Aspect Ratio Tolerance—if the Cell Aspect Ratios of both the cells in question are greater than this specified tolerance, then the chevron indicator is not computed and is set to 1. This tolerance prevents STAR-CCM+ from marking two irregular sized cells connected by a small face.
Position	The position vector represents the position or coordinates of a given location. It is available at vertices, faces, and cells. At faces and cells, the value represents the position of the respective face and cell centroids. This field function is the preferred option for specifying position dependencies of profiles and material properties when using field function methods.