[ana86]

Good Morning,

I like to simulate solidification in a closed system. At the fluid-solid interface I have to take the pull velocity into account. Does anyone have an idea how to write an udf for this case?
I have a rectangular model filled with a fluid. I only have walls on the left and the right side and also at the top. The bottom (x-axis) is the axis of rotation.
For the udf I need to implement the formula at the interface: q[W/m^2] = ug[m/s] * H[J/kg] * rho[kg/m^3] (ug = pull velocity, H = latent heat, rho = density)

Thank you for your help

[PKP_India]

Hi,
1. If you want to include pull velocity for the solidification, switch on the pull velocity and assign a constant velocity value for the pull velocity. so that the solidified cells can move with your given pull velocity.
2. if you want to write a UDF then compile a momentum source UDF and hook it to corresponding fluid cell zone momentum equations. Refer the UDF source manual for the more.

[ana86]

Thank you for your answer.
But I have already tried both suggestions, and did not get a reasonable result.

[PKP_India]

can you describe the problem in a detailed way, if possible?

[ana86]

I attached to pictures. At the first one you can see the modell. It is filled with fluid and at the upper wall I have a linear temperature boundary condition, so that one part of the fluid solidifies. Due to the solidification I have an additional energy source at the interface.
One problem is that my formula has the unit [W/m^2], while in Fluent you need the unit [W/m^3] as the energy source.

Thank you

[PKP_India]

I think the solidification model of Ansys fluent cannot explicitly track the interface. For this, you may need to look for the Eulerian multi-phase model (ex-VOF) to track the interface. There you can include the interface heat transfer model to account for heat flux due to solidification near the interface. Please look for solidification modelling using VOF in literature for this.

[ana86]

Thank you, I will try this approach.