[lyfflynice]

I tried to simulate the evaporator phenomena in a CO2 nozzle. The CO2 liquid and CO2 gas physical properties were defined by the RGP table in CFX solver. The pressure range is 0.6-16.6 MPa and the temperature range is 220-500 K. However, during the simulation, I encountered a waning "Independent variables went out of bounds while computing the variables listed below using the interpolation", as shown in Fig.1 And the Heat transfer and Turbulent RMS curves could not converge, as shown in Fig.2-3. As a result, the simulation gave a final error "Fatal overflow". The evaporator phase change model used the Lee evaporation-condensation model, and it was inputted the CFX by the CEL. The CCL file of my case was attached. Can someone give me some suggestions and point out the mistakes of my case setup? Thanks a lot!

[ghorrocks]

This is quite a complex model, so you need to make sure all the components are working by themselves before you put them all together.

I recommend running:
* Single phase compressible flow (maybe ideal gas or something simple) through the nozzle to check the basic compressible flow stuff is working.
* Then add an RGP gas (but still single phase)
* Add the multiphase stuff, but with simple incompressible materials. Also no phase change yet.
* Then add phase change with incompressible materials
* If all that is working then try adding the RGP properties to the multiphase model with phase change.

The bounds error often means that your simulation is not converging well and is diverging to non-physical values. You may need to widen the range of your table a bit to handle excursions during convergence, but more likely your simulation is just numerically unstable and you need to improve the stability. This can be done by:
* Better mesh quality
* Smaller time steps
* Double precision numerics
* Better initial conditions.

[lyfflynice]

Dear ghorrocks, I really appreciate your suggestions. The two-phase flow simulation with RGP tables using CFX has been reported in the open literature, so it was believed that CFX could handle with the current case. In my case, the mesh quality was good and the double precise was used already. Next, I will try to further decrease the time steps and improve the initial conditions. Thanks a lot again!

[ghorrocks]

Yes, CFX can handle all those simulations - but do you know how to set it up properly?

Just because somebody else has successfully completed the simulation does not mean you can successfully do it! You really need to get the basic simulations working properly before you do the full physics complex model.

[LUO DAN]

Originally Posted by lyfflynice

Dear ghorrocks, I really appreciate your suggestions. The two-phase flow simulation with RGP tables using CFX has been reported in the open literature, so it was believed that CFX could handle with the current case. In my case, the mesh quality was good and the double precise was used already. Next, I will try to further decrease the time steps and improve the initial conditions. Thanks a lot again!

Hi lyfflynice,
I have some questions about the generation of a RGP for co2.
1. You make a RGP through a generator you loaded or a code you wrote;
2. Can a generator generate a RGP for co2 in 2 phase;
3. How to set two phase flow in CFX pre with RGP.
I need your help.
Thank you very much!!

[alirezame]

Hello,

Try to increase the range of your RGP table to avoid clipping or extrapolating methods. Also, enable the Beta feature of CFX pre, then check the "RGP liquid properties (beta)"where you have loaded your RGP table.

[lyfflynice]

Originally Posted by alirezame

Hello,

Try to increase the range of your RGP table to avoid clipping or extrapolating methods. Also, enable the Beta feature of CFX pre, then check the "RGP liquid properties (beta)"where you have loaded your RGP table.

Thank you. The beta feature has been set in the CFX pre. I will try to increase the range of the RGP table.

[lyfflynice]

Originally Posted by LUO DAN

Hi lyfflynice,
I have some questions about the generation of a RGP for co2.
1. You make a RGP through a generator you loaded or a code you wrote;
2. Can a generator generate a RGP for co2 in 2 phase;
3. How to set two phase flow in CFX pre with RGP.
I need your help.
Thank you very much!!

Dear LUO DAN,
1.The RGP table generation code was written by myself with Matlab software.
2. The RGP generator can produce the gas phase and liquid phase CO2 properties, and the gas phase and liquid phase data were stored in two single file. But the two-phase CO2 properties can not be produced.
3. By inserting two materials, one is the gas-phase CO2, the other is the liquid CO2

[Saeef]

Originally Posted by lyfflynice

Dear LUO DAN,
1.The RGP table generation code was written by myself with Matlab software.
2. The RGP generator can produce the gas phase and liquid phase CO2 properties, and the gas phase and liquid phase data were stored in two single file. But the two-phase CO2 properties can not be produced.
3. By inserting two materials, one is the gas-phase CO2, the other is the liquid CO2

Hi，lyfflynice
I am working on SCO2 field as well， but in turbomachinery.
I also ceate a Matlab program which includes metastable properties by myself.
But it can only work well for single-phase situation.
I got some trouble in non-equilibrium flow.
Could we communicate it deeply ?
My Email address : liuzhiyuan@iet.cn

[lyfflynice]

Originally Posted by Saeef

Hi，lyfflynice
I am working on SCO2 field as well， but in turbomachinery.
I also ceate a Matlab program which includes metastable properties by myself.
But it can only work well for single-phase situation.
I got some trouble in non-equilibrium flow.
Could we communicate it deeply ?
My Email address : liuzhiyuan@iet.cn

Dear Saffe, I am very glad to have a deep communication with you. My email address: lyfxjtu@stu.xjtu.edu.cn. By the way, are you from China？ I am from China.

[LUO DAN]

Originally Posted by lyfflynice

Dear Saffe, I am very glad to have a deep communication with you. My email address: lyfxjtu@stu.xjtu.edu.cn. By the way, are you from China？ I am from China.

Dear lyfflynice,
I have a question. I'd like to know if the RGP file you generated contains the supercritical region, and if so, how do you distinguish the liquid phase from the gas phase in the supercritical region. I come from University of Shanghai for Science and Technology

[lyfflynice]

Originally Posted by LUO DAN

Dear lyfflynice,
I have a question. I'd like to know if the RGP file you generated contains the supercritical region, and if so, how do you distinguish the liquid phase from the gas phase in the supercritical region. I come from University of Shanghai for Science and Technology

Dear LUO DAN, the RGP file contained the supercritical region. In the supercritical region, the liquid phase and gas phase were not distinguished. We can communicate with E-mail.

[LUO DAN]

Originally Posted by lyfflynice

Dear LUO DAN, the RGP file contained the supercritical region. In the supercritical region, the liquid phase and gas phase were not distinguished. We can communicate with E-mail.

OK, thank you. When I have a problem, I will contact you.