HyperMesh CFD includes some alternate methods of calculating certain element types, which only apply to quads or rectangular faces of solids, and only include alternate checks for Aspect Ratio, Skew, Taper and Warpage.

Note: Because these methods apply only to certain quality checks, in order to use them you must choose the set individually option in the Check Element settings.
Aspect Ratio
ratio1 = V1/H1
ratio2 = V2/H2
Skew value is larger of ratio1 or ratio2.

Figure 1. Aspect Ratio
First, HyperMesh CFD constructs lines connecting the midpoints of each edge of the quad, dotted in the picture below. Next, HyperMesh CFD constructs a third line, green in the picture below, perpendicular to one of the initial lines, then finds the angle between this third line and the remaining initial line – with which is it most likely not perpendicular, unless the quad is a perfect rectangle.
α is the skew (angle) value.

Figure 2. Skew
First, the quad’s nodes are projected to plane defined by the orthonormal vectors U-V found as follows:
  • Z = X × Y
  • V = Z × X
  • U = X

Figure 3.

Figure 4.
In HyperMesh CFD, Taper angle is defined as: θ = max ( θ 1 2 ; θ 2 2 ) .
The optimal value is 0°, and a generally acceptable limit is. <= 30°. The The ultimate limit, which the Taper angle cannot exceed is 45°.
Only applies to quads or rectangular faces of solids.

Figure 5.
Warpage = 100 * h / max { Li }, where h is the minimum distance between the diagonals.