How to compute/model isentropic in CFD?

Shamoon Jamshed · July 12, 2023, 12:10

1. This question might not be asked in the right way, I was wondering is there any method that we can model and isentropic flow. I assume that it should be like (adiabatic + reversible) sort of thing. But how can we model it in a simulation?
2. If we cannot model can we achieve near to isentropic results? how?

Regards,

SJ

FMDenaro · July 12, 2023, 14:32

Quote:

Originally Posted by Shamoon Jamshed

1. This question might not be asked in the right way, I was wondering is there any method that we can model and isentropic flow. I assume that it should be like (adiabatic + reversible) sort of thing. But how can we model it in a simulation?
2. If we cannot model can we achieve near to isentropic results? how?

Regards,

SJ

Potential flows are such models… Unsteady Euler equations when no singularity is produced

Shamoon Jamshed · July 12, 2023, 14:50

Quote:

Originally Posted by FMDenaro

Potential flows are such models… Unsteady Euler equations when no singularity is produced

could you please elaborate, how can it be done? I think Euler or NS are just for equations, they are not directly related to isentropic condition

FMDenaro · July 12, 2023, 15:03

Quote:

Originally Posted by Shamoon Jamshed

could you please elaborate, how can it be done? I think Euler or NS are just for equations, they are not directly related to isentropic condition

I suggest to study the theory in a Gasdynamic textbook like Zucrow

LuckyTran · July 12, 2023, 15:05

If you take Navier-Stokes equations and turn off the heat transfer and turn off the viscous part, you get the Euler equations. The solution to the Euler equations is the solution you are looking for, so you might as well solve those equations.

If Euler equations do not exist in your universe, then you can use a Navier-Stokes based solver and calculate the irreversible parts of the process (i.e. the heat conduction and irreversible work) and then add these back as sources. For exampe if N-S is a+b = 0, and b=0 is Euler equations, then solving a+b=a is your isentropic Navier-Stokes that is an Euler equation but isn't an Euler equation.

It can be modeled, with Euler equations.

July 12, 2023, 12:10	How to compute/model isentropic in CFD?	#1
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 377 Rep Power: 18	1. This question might not be asked in the right way, I was wondering is there any method that we can model and isentropic flow. I assume that it should be like (adiabatic + reversible) sort of thing. But how can we model it in a simulation? 2. If we cannot model can we achieve near to isentropic results? how? Regards, SJ

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July 12, 2023, 15:05		#5
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,676 Rep Power: 66	If you take Navier-Stokes equations and turn off the heat transfer and turn off the viscous part, you get the Euler equations. The solution to the Euler equations is the solution you are looking for, so you might as well solve those equations. If Euler equations do not exist in your universe, then you can use a Navier-Stokes based solver and calculate the irreversible parts of the process (i.e. the heat conduction and irreversible work) and then add these back as sources. For exampe if N-S is a+b = 0, and b=0 is Euler equations, then solving a+b=a is your isentropic Navier-Stokes that is an Euler equation but isn't an Euler equation. It can be modeled, with Euler equations.