Wall BC

Richard Teo

I trying to simulate a flow around a pump in Ansys CFX. There are 3 parts to the pump. Straightener, impeller and diffuser. Only the impeller is rotating. Therefore, I create a enclosure around the pump, using it as the fluid domain. Then I cut the pump out, leaving only the fluid domain behind. After that, i slice the domain into 3 parts. The straightener, impeller and diffuser.

Now, what boundary condition should i use for the blade and hub. Should I rotate the fluid domain for the impeller , and use no slip wall for the blade, or should i leave the impeller domain stationary, then applied counter rotating wall for the blade? I am currently using the 1st scenerio, but the pressure generate in CFX post is way too high compared with the result obtained in older version of CFX(the one with CFX build and Tasc Flow) Why? Please help, any suggestion is welcome.