Perturbing boundary nodes in Tgrid.
By slightly perturbing boundary nodes of a surface mesh in Tgrid, skewness of the resulting volume mesh could be made low. Moving boundary nodes is especially advisable in situations where quads are split into tri's at the boundaries.
Following is the procedure to do so:
a)Compute approximately the smallest edge in the domain through Boundary--->Modify--->nodes,select two nodes of an edge and press distance.This would approximately give an edge distance.
b)Type (%jiggle-boundary-nodes 0.15) in TGRID console. "0.15" stands for the amount of distance the boundary nodes have to be perturbed. This can be estimated from edge distance computed from the above step. Please note that this is absolute distance,in the sense if an edge in the domain has a length of 1,then 0.15 is 15% of edge distance. Using a high value would distort the original geometry.
3)With the original face-mesh,a volume mesh can be generated by using (%jiggle-boundary-nodes 0.15) through TUI and Mesh-->Auto Mesh-->Init&Refine.