What is approach velocity and device velocity.I have faced this problem during defing blcoakeg.Also I have a few problems when defining blockages. First is in my case I have to define a blcoakge in a zone.In that blcokage there is 40 percent area is open.Actually there is some tubes at taht place ,but instead modelling them i have taken blckage because i know the pressure drop taking from those tubes.Now for that i have to define that 40 percent area is open.Soi how i can define it in fluent?second thing is how to define head loss co effcient for that? i have gone through manual in that ther are loss co eff like resistance loss co eff,diractional loss co eff etc etc.so is ther any relation of head loss with these co eff? and what is permeabilty here?Pls answer this ifanybody know. Thanks all of u in advance.

Supposed that you defined your "blockage" zone as porous media, you can set for example porosity = 0.4 (40% open volume...). You can also choose between superficial and physical velocity formulation, useful if you're treating heat transfer or unsteady flows. The pressure drop equation used in Fluent is the classic Darcy+inertial term so, once you have the head loss, just calculate your coefficients...according to the direction you want (for example, if you want the fluid to flow only in 1 direction, you can put really big coefficients of pressure drop in the other directions (say 1e10)...

Hope this can help.

Edi.