Relative Expression

This option allows you to specify a simple text expression to set the relative size of the mesh on all geometric faces within the surface group. You must enter the expression in the text entry area provided. The expression may be a function of x, y ,z coordinates, and must follow the syntax described in the appendix. The following example illustrates an expression that enforces a mesh size of 0.05 at "z" locations greater than or equal to 0.25, and a mesh size of 0.125 at z locations having a value less than 0.25. value = if( z >= 25, .05, .125).

The size that results from the expression is then multiplied by the length of the longest edge of the bounding box that encloses each geometric face. This produces the final mesh size that the surface mesher tries to enforce. Note that the surface meshing algorithm will attempt to satisfy the sizes specified by the expression, but the final mesh size will be subject to adjustment due to limits on the rate of transition between adjacent sizes, smoothing, and so on.

Using this expression the mesh shown below is generated. Here the number of layers along the edge of z = 0 is eight elements, since below z =0.25 the element size is specified by the largest length on the model time 0.125. The edge at z=1 has approximately 20 elements across as a relative mesh size was specified of 0.05.

Figure 1.