[sampy]

Hello everyone,
I am final leg of my UDF development. In order to successfully complete it, I require the knowledge of critical pressure of the fuel. I employ both single component and multi-component fuel surrogates in my current study. So, can I retrieve the critical pressure from any of the shared header files or do I need to provide this information as an user input?
Thanks in advance.

[sampy]

Hello everyone,
Converge does use the critical pressure in the Homogeneous Relaxation Model (HRM) it uses in modeling cavitation. I am not modeling cavitation currently but I am working on something related to HRM and would require the knowledge of the critical pressure of the liquid/parcel in order to go forward. So, I would like to know how to access this information.

I have gone through the manual and do understand that gas critical properties can be accessed directly using crit_temp and crit_pres but these are not of interest in the current scenario.

I would appreciate any kind of help on by the members of this forum.
Thanks,
Sampath

[ywang89]

Originally Posted by sampy

Hello everyone,
I am final leg of my UDF development. In order to successfully complete it, I require the knowledge of critical pressure of the fuel. I employ both single component and multi-component fuel surrogates in my current study. So, can I retrieve the critical pressure from any of the shared header files or do I need to provide this information as an user input?
Thanks in advance.

Hi Sampath,

You can access the critical temperature and pressure of liquid species like this
critical_temp=liquid_critical_temperature_table[isp_liq];
it_crit=(int)(critical_temp/10.0);
critical_pres=liquid_pvap_table[isp_liq][it_crit+1];
isp_liq is the index of the liquid species. If you have only one liquid species, isp_liq=0.

Thanks,

[sampy]

Hi Yunliang,
Thank you for the assistance and sorry for getting back so late on this. I have a follow up question concerning the critical pressure. The solution given by you spits on the critical pressures of the individual components in a mixture. Is there a way Converge calculates the overall critical pressure of the mixture or does Converge calculates the critical pressure a mass weighted or mole fraction weighted average (pseudo critical pressure)?
Thanks,
Sampath

[ywang89]

Originally Posted by sampy

Hi Yunliang,
Thank you for the assistance and sorry for getting back so late on this. I have a follow up question concerning the critical pressure. The solution given by you spits on the critical pressures of the individual components in a mixture. Is there a way Converge calculates the overall critical pressure of the mixture or does Converge calculates the critical pressure a mass weighted or mole fraction weighted average (pseudo critical pressure)?
Thanks,
Sampath

Hi Sampath,

As CONVERGE can handle liquid with multicomponents, CONVERGE doesn't calculate the mixture critical pressure using mass weighted or molar-weighted average. If your model needs to do so, you can easily calculate it. For VOF simulations, it will be more accurate to consider individual critical pressure than to use the mixture critical pressure.

Thanks,

Yunliang

[sampy]

Hi Yunliang,
Thank you for your response. So, Converge does not calculate the overall critical pressure either numerically based on an EOS or a pseudocritical pressure sorts using mass or mole fractions?

I am currently modelling sprays and not using VOF simulations. I have to calculate a non-dimensional pressure which is based on the critical pressure of the mixture/surrogate that I am using. For the time being I am calculating the pseudo critical pressure based on the mass fraction of the individual components, I am looking for a better estimate of the critical pressure.

Also, is there a way to access the molecular weights of the parcel species (not the gas species)?
Thanks,
Sampath

[ywang89]

Originally Posted by sampy

Hi Yunliang,
Thank you for your response. So, Converge does not calculate the overall critical pressure either numerically based on an EOS or a pseudocritical pressure sorts using mass or mole fractions?

I am currently modelling sprays and not using VOF simulations. I have to calculate a non-dimensional pressure which is based on the critical pressure of the mixture/surrogate that I am using. For the time being I am calculating the pseudo critical pressure based on the mass fraction of the individual components, I am looking for a better estimate of the critical pressure.

Also, is there a way to access the molecular weights of the parcel species (not the gas species)?
Thanks,
Sampath

Hi Sampath,

You are right that we don't calculate the mixture critical pressure or temperature since we don't need them. The molecular weight of liquid parcels can be accessed via the way below

for(isp=0;isp<num_parcel_species;isp++)
{
isp1 = parcel_species_lookup[isp];
parcel_mw=species[isp1]->mw;
}

Thanks,

Yunliang

[sampy]

Hi Yunliang,
Thank you for the assistance provided during the course of last couple of couple of weeks, really appreciate the help.
Thanks,
Sampath