[ikhaleb]

Hi all!

I'm a masters students in nuclear engineering and I am new to CFD. I'm doing a research in CFD analysis on molten salt reactor. Currently, I modeled a a slab geometry with nuclear fuel salt (2.5mm), wall(1.0mm), and coolant salt(2.5mm). The slab geometry is 3400 mm height. I'm using K-Omega turbulence model. Previously I ran an analysis with a coolant inlet velocity of 5.0 m/s and 840K inlet temperature and the simulation converged well.

For the geometry, I created a small 0.1mm height of these three components and then I extruded the mesh. After several iterations, I keep increasing the mesh size (number of layers of mesh).

Now, I'm running a simulation with inlet velocity and temperature of 2.5 m/s and 775K. However, my simulation does not converge (specifically my energy residual is pretty high). Previously it took me about 11,000+ iterations to see some solid solutions/results. But now, even after 20,000+ iterations the results still do not converge. My maximum temperature is also climbing up as if it's heading to the moon!

Is there a possibility that the new velocity/temperature is not suitable?
I'm kinda puzzled, as I only changed the velocity and temperature inlet BC.

Help me! I have stuck on this problem for nearly 3 weeks now!

I'm attaching some of the photos from the simulation for your references. I also added a previous simulation result on 5 m/s and 840K inlet velocity and temperature of coolant.