Medina-specific checks used to calculate element quality
for 2D and 3D elements.
Additional element checks not listed here are not part of the solver’s normal set of
checks, and therefore use HyperMesh check methods.
2D and 3D Element Checks
These checks apply to both types of elements, but when applied to 3D elements they
are generally applied to each face of the element. The value of the worst face is
reported as the 3D element’s overall quality value.
Aspect Ratio (Edge Ratio)
Edge Ratio is calculated as the ratio between an element’s shortest edge
and its longest edge; For the sake of consistency, HyperMesh CFD inverts this result,
effectively making it the ratio of longest to shortest, and reports the
result as the element’s aspect ratio.
Interior Angles
Maximum and minimum values are evaluated independently for triangles and
quadrilaterals.
Jacobian
Deviation of an element from its ideal or "perfect" shape, such as a
triangle’s deviation from equilateral. The Jacobian value ranges from
0.0 to 1.0, where 1.0 represents a perfectly shaped element. The
determinant of the Jacobian relates the local stretching of the
parametric space which is required to fit it onto the global coordinate
space.
HyperMesh CFD evaluates the determinant of
the Jacobian matrix at each of the element’s integration points, also
called Gauss points, or at the element’s corner nodes, and reports the
ratio between the smallest and the largest. In the case of Jacobian
evaluation at the Gauss points, values of 0.7 and above are generally
acceptable. You can select which method of evaluation to use (Gauss
point or corner node) from the Check Element
settings.
Length (min)
Minimum element lengths are calculated using one of two methods:
The shortest edge of the element. This method is used for
non-tetrahedral 3D elements.
The shortest distance from a corner node to its opposing edge
(or face, in the case of tetra elements); referred to as
"minimal normalized height".
Figure 1. Length (min)
Maximum Angle
Largest angle between adjacent edges of the element is reported.
Minimum Angle
Smallest angle between adjacent edges of the element is reported.
Skew
Element’s interior corner angles are compared to 90 degrees (for quads)
or 60 degrees (for trias). The absolute values of these deviations are
summed and reported.
Taper
Quadrilateral elements are split into two triangles. Figure 2. Taper
The area of the smaller of the two triangles is compared to the
total area of the quadrilateral. In Figure 2, .
Note: To improve consistency with other
taper checks, HyperMesh CFD displays a value
of 0.5 minus this value so that 0 implies no taper. However, this is
not completely consistent with other taper checks, because in this
case taper ranges from 0 (no taper) to 0.5 (full taper), whereas
HyperMesh CFD’s own taper check reports a
1.0 for full taper.
Warpage
Elements with more than three nodes are split into triangles. The
largest angle between the normals of triangle pairs is reported as the
warpage.
3D Element Only Checks
Medina does not use any 3D specific checks. HyperMesh CFD uses its own checks instead.
