RGP table error

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• Last Post 04 March 2019
abbas posted this 13 February 2019

Hello every one,

I have three questions about RGP table and two-phase flow in CFX.

1- When I generate the RGP table, I should consider the minimum and maximum pressure for the table and as well for temperature. Because static is smaller than total pressure, should I consider the static pressure for the minimum pressure in the RGP table and total pressure for maximum pressure?

2- For two-phase flow in CFX, it is recommended that let the problem to be solved without solving the volume fraction equation and letting the velocity and pressure fields develop for some hundreds of iterations. How can I do that in CFX?

3- has anyone could use RGP table and solve the two-phase flow problem?

best regards

Abbas

abenhadj posted this 13 February 2019

1/Are you talking about table generation in CFX? The pressures are always absolute pressure

2/Where have you seen that recommendation? I would just enable coupled volume fraction if you have a  lot of non-drag forces. If it is not running from the beginning start with segregated volume fractions.

3/My last work with RGP was as I investigated boiling analysis.

Best regards,

Amine

abbas posted this 13 February 2019

I don't think that the coupled volume fraction or segregated volume fraction is available when we use the homogenous model.

Could you let me know your idea?

Best

Abbas

abenhadj posted this 13 February 2019

No you are right:  is not available as you are using component conservation equations (not really multiphase model if we talk about the CFX models). But for homo.and inhomo multiphase flows it is available.

Best regards,

Amine

abbas posted this 13 February 2019

Yes. I create two materials namely: co2 vapor and co2 liquid and I use homogenous mixture model. Therefore, a coupled volume fraction or segregated volume fraction was not available on Advanced option in CFX.

Is there any tutorial except axial turbine tutorial for simulation of two-phase in CFX and using RGP table?

Thanks

Abbas

abenhadj posted this 13 February 2019

No Abbas, I am not aware about any other available and official tutorial. So you are working with pure binary mixture and not with two phase each one of them is related to a phase?

Best regards,

Amine

abbas posted this 13 February 2019

Yes, Actually I am working on the pipe simulation that at inlet I have supercritical situation ( P=9Mpa and T=310K) but in the outlet, I have two-phase (P=5Mpa).

I use RGP table from AFD and my mesh quality is higher than 0.5 for more than 99% of the model.

Best regards,

Abbas

abenhadj posted this 13 February 2019

Infinite mass transfer is assumed here to have thermodynamic and mechanical equilibrium. So judging the quality of the results would require some validation. You can verify using a non-equ. approach but won't make a sense for me without having data to compare.

Best regards,

Amine

omidne posted this 04 March 2019

Hello Dear Abbas

I have asked for RGP table generation, Could you please guide me for RGP table generation?

Sincerely your

Omid