[sinaited]

hi

i want to set up a simulation for a tank with varying velocity boundary. the velocity depends on the tank pressure. velocity is a power law function of pressure in tank and also the tank is expanding(the wall is moving).
1-what UDF should i use?
2- can i use "named expression" in UDF?( i defined an average pressure in named expression and i want my UDF to be able to read this average pressure.)
3- when i define the mass flow rate as an expression, this error shows up {Incorrect expression unit. Expression Unit [m s^-1], Required Unit [m s^-1]}. the dimensions are correct and error seems unreasonable. have you ever encountered this problem?

[AlexanderZ]

1. if you are going to use UDF read Ansys Fluent Customization manual, look for DEFINE_PROFILE macro
2. if you are going to use UDF, you may define all boundary conditions here. Or calculate pressure again
3. show expression which you put

[sinaited]

this is my expressions i defined, can i use one of my expressions like "P_avg" in UDF profile?

[vinerm]

I am unsure if the expression could be used if it depends on another expression that uses field values, such as, pressure in the domain.

Prefer UDF. For most of the boundary conditions, you need to use DEFINE_PROFILE. Since the pressure in the tank is not a single value, you need to reduce it to a scalar, either using an average or maximum or minimum, depending upon your requirement.