Learning Forum

[rachels1001]

My current simulation involves a packed bed with the bed travelling along a grate through a series of drying sections. The contents of the packed bed are initially wet, and are expected to undergo complete evaporation of their water content in the first couple of drying sections. I am using the Lee evaporation model for this, and previously my temperature and evaporation URFs were 0.1 and 0.1 respectively and my evaporation constant was 0.1. I would increase the temperature URF to 1.0 over the course of the simulation run between iterations. However, I was noticing that not all of the water was evaporating in the first couple of drying sections, and occurring later, ruining the reactants temperature profile. 

To help this, I increased the evaporation constant to 0.3. I selected this values based on calculations of the expected evaporation constant from the Ansys Fluent theory guide. 

The simulation was able to fully converge before when run with an evaporation constant of 0.1; however, it now diverges at the point when the temperature URF is increased to 0.8 during the course of the simulation. 

Are there any common practices people use to avoid divergence in this kind of case?

[rachels1001]

Update: I'm still occasionally struggling with this issue, and some of the typical strategies that have worked in the past (increasing URFs more slowly, having more iterations between increasing URFs) aren't working for a current simulation that I'm working on.

If anyone has any tips that they've picked up, I'd be really interested in hearing them!