[tatiana33]

Hello,

I am developing a 2-D depressurization model for pipelines transporting pure CO2. The model is transient/unsteady and my domain is a rectangle that represents the inside of the pipeline. I am using ANSYS Fluent. I am currently facing convergence issues when using the Peng-Robinson EoS. Apparently, the residual with the worst behavior is the radial velocity (y-velocity), which is particularly unstable close to the upper wall of the pipeline. I have tried different meshes with different y+ values, as well as different turbulence models. Unfortunately, I have not been able to run the model for more than 24 time steps (Deltat:10^-7s).
A summary of my model settings is next:
- Density based axysimmetric.
- Turbulence models: I have tried standard k-epsilon, realizable k-epsilon and k-omega SST.
- Energy: on
- Boundary conditions: inlet-wall, upper wall, axisymmetric, pressure-outlet.
- Implicit formulation.

I will really appreciate any input or suggestion on this matter. Thanks!