Decreasing skewness of volume mesh in Tgrid
There might be instances when the skewness of volume mesh needs to be decreased from the maximum value. Once volume mesh is created from the surface mesh, following steps could be adopted to decrease cell skewness in TGRID.
1)Read the surface mesh into TGRID and change dead zone to fluid zone through Mesh--->Tri/Tet--->Controls--->Init/Mesh-->fluid.
2)Mesh the geometry through Auto Mesh--->Init & Refine. Incase,if initial attempt fails, clear the mesh through Mesh--->clear and repeat Auto Mesh--->Init &Refine.
3)Check number of cells having skewness greater than 0.95 through Display--->Plot--->Cell Distribution--->Minimum=0.95,Maximum=1,Partitions=1.
4)Let us say, there are 4 cells in the range of 0.95-1.00.
5) Display the 4 cells through Display--->Grid--->Cells-->select all the fluid zones,switch Quality,Cell Quality Range-->minimum=0.97 and maximum=2.0.
6)Autoscale the cells through Display--->Views--->Auto Scale.
7)Select any node of a cell by clicking at the node as shown at <a target=_blank href="http://www.fluentusers.com/support/solutions/1015/node.gif">http://www.fluentusers.com/support/solutions/1015/node.gif</a>http://www.fluentusers.com/support/solutions/1015/node.gif
8)Display only the selected cell through Display--->Grid--->Bounds--->Click Set Ranges--->Click Display. Again autoscale the cell as in step 6. The cell is seen as in cell1.gif file.
9)Reselect an appropriate node of the cell and switch to "position" in Boundary--->Modify panel. Select an appropriate position just below/above the node as shown at <a target=_blank href="http://www.fluentusers.com/support/solutions/1015/cell1.gif">http://www.fluentusers.com/support/solutions/1015/cell1.gif</a>http://www.fluentusers.com/support/solutions/1015/cell1.gif . Click the radio button "move".
10) Compute the cell skweness through Display--->Plot--->Cell Distribution. If the cell skewness is GREATER than 1.0 ,then the "position" has been selected in wrong direction which results in negative volume of cell. This can also be seen from grid check. Undo the operation through Boundary--->Modify--->Undo.
11)Repeat step 9 by selecting position appropriately. Similarly move other nodes of the cell under consideration till the cell disappears automatically from the screen indicating the skewness of the cell is less than 0.95.
12)Display remaining cells by going to Display--->Grid--->Bounds--->Click Reset--->Display.
13)Repeat steps 7 to 12 till all cells disappear from the display. The whole setup of steps 7-12 is shown at <a target=_blank href="http://www.fluentusers.com/support/solutions/1015/setup.gif">http://www.fluentusers.com/support/solutions/1015/setup.gif</a>http://www.fluentusers.com/support/solutions/1015/setup.gif
14)Once the skewness of the cells is less than 0.95,it can be saved and read into Fluent.
The procedure is fairly simple once you get acquainted to it.