Learning Forum

[a.ebrahimi]

The problem that I am dealing with is related to simulating multiphase melting and re-solidification of a moving body using ANSYS Fluent. 

 

The physical problem is a solid slab which is moving at a constant speed and is heated locally above its melting point with a stationary heat source. The heat source is applied by defining an energy source term at the material-air interface. I used the VOF model to free surface deformations of the molten region. Figure 1 shows a similar problem simulated in other software by others.

 

To numerically model this problem in ANSYS Fluent, I made a case and employed the “velocity inlet” boundary condition at the inlet to determine the slab and air velocities and an “outflow” boundary condition at the outlet. However, after running the simulation I found that the solidified region close to the boundaries moves and deforms, which is physically unrealistic (see figure 2).

 

Any heads up, or hints on how to model this problem in ANSYS Fluent using a moving reference frame (i.e. without modelling the source-term movement explicitly) are highly appreciated.

[Rob]

Don't use an outflow bc: they're not suitable for VOF (or anything much now). If you're setting a velocity boundary Fluent must push that much material into the domain: check the pressure in your model as it could be fairly high. 

[a.ebrahimi]

Thanks for your reply.

What would be a good setup for the boundary conditions in this problem?

What is known in this problem is the velocity of the workpiece at the inlet boundary and we do not know what is the surface morphology when it leaves the domain to prescribe a velocity. The value of the pressure and its distribution is also unknown since the solidification model for all relative velocities to be zero in the solid region at the outlet. 

[Rob]

Not sure without going into a lot of detail which I can't on a public forum. 

One option would be to fix the solid and move the heat source: that neatly avoids the problem? 

[a.ebrahimi]

The intention is to avoid using the moving heat source since it will eventually increase the computational costs. 

[a.ebrahimi]

Is there a private forum for ANSYS customer? how can I ask this question in the private forum?

 

[Rob]

We have the Customer Portal, via ansys.com for commercial customers. This is not open to students, but your supervisor (or department expert) may be able to log a query. 

[luigilusini]

Dear cfdstar! 

I have the same task, but unfortunately I could not make the model. Can you help me?

Thanks for advance...

 

[Amine Ben Hadj Ali]

I would go with having a moving heat source per UDF.