hi,all I have trouble to define an outlet of gas-solid two phase flow in CFX44, where gas phase can pass through while solid phase can't. How can i achieve this. I am using an euler-euler solution.

Youngan,

You can't inhibit one of the phases at an outlet. However, there is something in CFX-4.4 called a degassing boundary. It was originally intended to remove bubbles from the surface of a liquid tank. The tank surface is defined as a "wall" and the bubbles incident on the wall are removed with a source term while the liquid remains.

There's no reason this can't be used for your gas-solid flow. I think that the command file implementation of the degassing boundary removes phase #2, so you'll have to make sure your solids are phase #1 and that the gas is phase #2.

What do you plan to do with the solids build up at the exit? This might present a problem.

Jeff