[Michelle197]

Hi all,

I am new to star ccm+ so this is probably a stupid question.
I have a cube and I want to prescribe the velocity on the cube faces to create a uniaxial extensional flow: velocity = [strain_rate*x,-strain_rate/2*y,-strain_rate/2*z]. So what I did is created a velocity_inlet boundary condition on the surfaces. Since the velocity depends on the local coordinates on the surfaces I thought it was best to define it via a field function, but I can not figure out how this works. I want to have a strain_rate of 1, but I don't know how to set a user variable. I tried to define a user field function but I keep getting syntax errors because the dimension is not right: [$$Position[1]*1, -0.5*$$Position[2],-0.5*$$Position[3]].

I also saw that there is a velocity field function, so I tried to add that to the boundary condition, but now I can't find how to define the velocity.

Can anyone please help me out? Thanks in advance!

Kind regards,
Michelle