# UDF for transient boundary condition?

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 November 20, 2003, 22:06 UDF for transient boundary condition? #1 Shankar Guest   Posts: n/a Hello everybody, If I treat the flow through U-tube as a transient problem, can I have a boundary condition (pressure inlet at the left handside and H left > H right) which will be a transient boundary condition, because as water level in the right hand limb keeps increasing there is a drop in the pressure as time progresses and flow would stop at delta H =0. This boundary condition I have formulated needs to calculate the volume of the water entering the inlet. Is it possible to write an UDF for this which would need the volume of water entering to be read from FLUENT. Or do you have any suggestions? Best Regards, Shankar. hayet likes this.

 November 22, 2003, 08:10 Re: UDF for transient boundary condition? #2 ccc Guest   Posts: n/a hi Shankar, I am not very clear about your problem, but only for the caculation fo the volume of water entering the inlet, it is possible to do it with udf. first you can get the flux on the inlet by multiplying the velocity and the aera and then integrating the flux along the time gives you the volume. good luck. btw, the following macros can be helpful, F_U, F_V, F_W, F_AERA, NV_DOT,