RGP table warning

  • 44 Views
  • Last Post 09 December 2018
abbas posted this 09 December 2018

Hello everyone,

 

I am modeling CO2 as a two-phase flow that the flow as a supercritical enters into the tube and after that, I will have two phases (vapor and liquid) because pressure decreases. 

I used Ansys AIM to generate the RGP table, so I am not worried about the RGP table. However, when I used HEM, after some iterations I will get the overflow error. Therefore, at first I start the simulation with a single phase for 700 iterations and there was no error (no overflow error or warning message about Table bounds warnings). So I used the single phase results as my initial condition for two-phase. The good thing that the iteration doesn't stop and I haven't got an overflow error but I received the Table bounds warnings. I think that my setup case doesn't have a problem because it worked with one phase.

 

I would be grateful for your help.

Abbas

Order By: Standard | Newest | Votes
abenhadj posted this 09 December 2018

I do not think so but a symmetric geometry does not mean symmetric flow. But you are using periodic boundary so I think this relaxation is okay.

Best regards,

Amine

abbas posted this 09 December 2018

Now, I am using med-high RGP table from ANSYS AIM. Therefore, the problem shouldn't be about table resolution. My model is symmetry so I modeled just 90 degrees of the model and I used CFX interface based on rotation so in this cade whole model will be simulated. Do you think that interface might be a problem and I should model whole geometry?

 

Best regards

Abbas

abenhadj posted this 09 December 2018

A very loose resolution of the table is bad. If you keep getting the warnings during the iterative process then something is wrong either in the setup or it lies on the RGP.

Best regards,

Amine

abbas posted this 09 December 2018

I used the single phase to assure that the case setup and operating condition are well defined. I used HEM for co2. I generate the table for 2MPa to 2MPa and temperature 250K to 450K. My inlet parameters are pressure inlet=12MPa and temperature=320K.

The model is symmetric so for computational cost, I just model 90 degree and define the rotating interface.

 

 

abenhadj posted this 09 December 2018

Why do you think that if it is running in single phase that it might work for two phase? For your actual run are you using the HEM or HEM within multiphase framework?

You might be lucky and the warnings vanish or you need to widen the table ranges and check your setup.

Best regards,

Amine

Close