Hi All

I am tryin to model the flow through an impeller using CFX-TASCflow 2.12. I know my inlet BC's very precisely..i specified inlet total pressure / total temperature and velocity. but i dont know my impeller exit conditions so i just specified massflow rate at the outlet. but its giving me problem. it stops after couple of iterations with liner solver overflow error. if anyone has done similar kind of simulations or if someone could help me out. i am a new bie to TASCflow and dont know much in detail abt TASCflow.

thanks a million in advance

If outlet BC is placed far enough downstream, you can make a good guess on what to impose. E.g, if radial impeller, constant static pressure is reasonable first guess and if axial, radial equilibrium is good. Since you are using the term "impeller", I am assuming a radial (aka centrifugal) blade. Imposing mass flow can be a dangerous approach. For example, for compressible flow, imposing a mass flow rate higher than the choked flow will lead to no solution. Also might want to check outlet flow – if it is radial impeller and you are extending BC out far, you can get too much diffusion resulting in highly separated flow at the outlet BC – not a good numerical situation. One strategy to avoid this is to "pinch" the diffuser in a prescribed manner to control the radial diffusion.

Thanks buddy

actually, i just have an impeller.. so i am imposing massflow directly on the outlet area of the impeller. i dont have any data about the pressure.. i know my inlet static pressure. do you think if i assume say half of the pressure rise across the impeller , as i know the pressure ratio, and make a guess of static pressure.. will that work ?

regards