Learning Forum

[raju.chowdhury]

Previously, I developed a VOF-based multiphase model to simulate the bubble rise in a hot liquid along with a solidification submodel. The gas density was calculated from the Ideal Gas law. I used adaption meshing in a particular region to get the fine mesh. I used the 2019R3 version of Fluent and got the expected result. However, I am running the same simulation (without modifying anything. Using the same case and data file as before) using the 2023R1 version of Fluent and the bubble is moving down instead of rising. 

I am not sure why getting this unexpected result.

Please note that when I change the density (gas—secondary phase) from the Ideal gas law to a constant, the bubble rises.

 

Sharing your thoughts on resolving the issue would greatly help me.

Thanks.

[Rob]

Check the operating density. From memory 2019 used a fixed but 2023 defaults to phase average or lightest phase. 

[raju.chowdhury]

In both cases, the operating density was set as 0.

[Rob]

Odd, I've not seen any issues with the VOF model in the last several builds. What does 23R1 think the ideal gas density is?

[raju.chowdhury]

 

Running the same case in 2021r1, getting the expected outcome (Bubble rises). While using 2023r1, the bubble moves downwards! In both cases, operating density is 0 and gas density is calculated from ideal gas law.

Any idea how to solve the issue?

 

[Rob]

This is the first time I've seen this, and I cover multiphase as a focus topic in Europe. If you right click on the various section headers in the tree you'll see "list modified settings". What doesn't agree with what you expect?