This might be worth a read:
http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

I would suggest you search this forum about the problem of negative pressure and then open a new thread about this problem providing screenshots, out-file and a good description.
Otherwise this thread here gets too far off-topic now I think.

hi
I am facing a similar problem "There is no valid outlet domain to mesh. The outlet domain will be turned off" I was reading your solution but i am new to turbo grid can you guide me how I can orient my coordinates in order to solve this problem. hope to hear from you soon.