Hi All, I am simulating a 3D case and my case was working fine in 2D, after run it in 3D it keeps crashing. I have a serious problem in the outlet BC and I tried to use higher order BC and still crashing My case outlet BC is -------------------------------------------- <REGION REF="5"> <!-- Outlet --> <N VAR="u" USERDEFINEDTYPE="HOutflow" VALUE="0" /> <N VAR="v" USERDEFINEDTYPE="HOutflow" VALUE="0" /> <N VAR="w" USERDEFINEDTYPE="HOutflow" VALUE="0" /> <D VAR="p" USERDEFINEDTYPE="HOutflow" VALUE="0" /> </REGION> ----------------------------------------------- any suggestions? Also if i can creat a buffer zone how i can do it with different viscosity, or can i specify "SpectralVanishingViscosity" to a specific zone not for all the domain. Regards, Cheers, Reda PhD student Aerospace Dep UPC Spain