Hello every one, can you give me some ideas...how to delete cracks..can we delete directly or we have to use any command...

please help me in this regard

A crack is not something you can delete. Its an indication of an error in your mesh that you have to fix. A crack exists because the mesh is not topologically continuous. It may be that you have to merge coincident vertices (VMERGE) or if you have non-matching cells you have to create couples (CPMATCH).

As a Continution of the above, is it possible to give boundary condition where Couple is created? suresh

It is very important to delete cracks, as they occur as a wall in the fluid domoian. Because no couple is defined for a crack, ofcourse no couple error will be shown. I fix it this way. - let Nav-Center make a cset of the cracks - give the cset a new cell id, to locate the cells every time without makeing a very time extensiv crack-check again. - cset from one failed mesh location. - grow set to have a master and all there slave cells. I make a vset to add cells to that cset. - be sure that in the cset every master cell has all his slave cells, because when you delte a possibly couple a such an uncomplete pair of cells you generate a couple error. - generate a new couple. - give back the repaired cell set the original cell id. - look at another failed mesh location.