When the current CAE dimension is set to 2D, this diagnostic function is available for structured domains
only. On the other hand, when the current CAE dimension is set to 3D, the function is available for structured and
The Jacobian is computed for each cell in the following way:
- Quadrilateral: The Jacobian is computed calculating the scalar triple product at each corner of a given cell using points from that cell
and a normal vector computed from the bounding box of the grid system. The final Jacobian for the cell is the average of all the corner Jacobians.
Caution: Since the normal to the cells is obtained from the bounding box of the grid system, the Jacobian computation is only accurate
for the particular case of flat structured domains aligned with the positive direction of one of the main axes.
- Hexahedron: The Jacobian is computed by calculating the scalar triple product at each corner of a given cell using only other grid
points from that cell and then calculating the average value of all the corner Jacobians.
- Prism: The Jacobian computation consists of computing the triple product at each cell corner using only other grid points from
that cell and then computing the average value of all the corner Jacobians. The average value is then pre-multiplied by a coefficient of 0.5.
The options in the Options frame allows you to quickly decide which cells to visualize according to their Jacobian value (Positive, Positive Skew, Zero,
Negative Skew, and Negative). You can also see the number and percentage of cells for each Jacobian Category.
Note: In general, we do not recommend toggling on all the Jacobian categories at once (shown above). Doing so, would cause all the cells
in the domain or block to be rendered at the same time making it very cumbersome to distinguish bad cells from good cells. Furthermore, simultaneously
displaying all cells in a large mesh can be computationally expensive.
Positive, Positive Skew, Zero, Negative Skew, and Negative Jacobian cells can be individually rendered in the
Display window by toggling each type in the Options frame (shown above). The number and total percent of cells for each Jacobian Category
can be seen in the Count and Percent columns. These cell Jacobians are classified according to the table shown below:
||Average Value of Corner Jacobians
||Sign of Corner Jacobians
Tip: If you note that your domain or block has all negative Jacobians, this is a sure sign that the computational orientation of your
block is left-handed. Use the Edit, Orient command to correct the orientation and ensure that all of
your domains and blocks are right-handed before exporting your mesh.