it seams that Star-cd can not overlap objects like Ansys. it is not very convenient. and it also have no function of undo. because we often make small mistakes, such as delete one cell by default, how can we fix this problems. maybe my question is too naive.

You cannot overlap cells in the STAR-CD solver (yet - its coming) anymore than you can overlap elements while solving an ANSYS finite element stress analysis, so you need to be more specific. What kind of objects are you talking about and what part of the STAR-CD suite are you trying to overlap something? pro-STAR has a VUNDO command which allows you to undo the result of any vertex change and it has a CUNDELETE command which allows you to undelete deleted cells. As a last resort you can always go back to the last SAVE and very easily play back all the commands generated (even by the GUI) stopping just before the mistake.

thanks a lot Mr, steve