[Phigo90]

Hi everyone,

I just want to know if anyone has any experience in using the intercondensatingevaporatingfoam in Openfoam? I try to use it to simulate an evaporating process of liquid nitrogen. However, first of all, I want to understand the general governing equation system and so on. Does anyone know any useful literature (e.g. paper, books) for this kind of problem?

Kind regards from Germany
Philipp

[massive_turbulence]

Originally Posted by Phigo90

Hi everyone,

I just want to know if anyone has any experience in using the intercondensatingevaporatingfoam in Openfoam? I try to use it to simulate an evaporating process of liquid nitrogen. However, first of all, I want to understand the general governing equation system and so on. Does anyone know any useful literature (e.g. paper, books) for this kind of problem?

Kind regards from Germany
Philipp

You could start here and understand the discretisation of the Navier-Stokes equation 2.1.8 Discretisation Procedure for the Navier-Stokes System

http://infofich.unl.edu.ar/upload/3b...7523c8ea52.pdf

Here's an attachment 3be0e16065026527477b4b948c4caa7523c8ea52.pdf excerpt from Santiago Márquez Damián-Final Work-Computational Fluid Dynamics
Description and utilization of interFoam multiphase solver.

[Phigo90]

Thanks a lot for your suggestions to have a good start in using OpenFoam. I've already worked with the buoyant and chtmultiregionfoam, so I am not an absolute beginner. but close to it.
I've checked your literature references.
I think it's a good idea to start with the interFoam multiphase solver to get a better overall comprehension (e.g. the VOF method, ...). I will give you feedback as soon as something new has emerged.

[massive_turbulence]

Originally Posted by Phigo90

Thanks a lot for your suggestions to have a good start in using OpenFoam. I've already worked with the buoyant and chtmultiregionfoam, so I am not an absolute beginner. but close to it.
I've checked your literature references.
I think it's a good idea to start with the interFoam multiphase solver to get a better overall comprehension (e.g. the VOF method, ...). I will give you feedback as soon as something new has emerged.

I've looked over buoyantPimpleFoam but lately I've been looking over its files line by line making sense of the individual steps to see why they work. I think a good starting point is interFoam or PisoFoam. Both are super basic.

[Phigo90]

Originally Posted by massive_turbulence

I've looked over buoyantPimpleFoam but lately I've been looking over its files line by line making sense of the individual steps to see why they work. I think a good starting point is interFoam or PisoFoam. Both are super basic.

Okay, so you would recommend to first have a detailed look at the interFoam multiphase solver (literature reference of your first post) and not to go directly to the source code of the intercondensatingevaporatingFoam?

[massive_turbulence]

Originally Posted by Phigo90

Okay, so you would recommend to first have a detailed look at the interFoam multiphase solver (literature reference of your first post) and not to go directly to the source code of the intercondensatingevaporatingFoam?

Whichever makes more sense to you, understanding PISO and SIMPLE are key though. If you look at the source code for complex solvers you'll notice that they are built around the simpler solvers.

[Phigo90]

Originally Posted by massive_turbulence

Whichever makes more sense to you, understanding PISO and SIMPLE are key though. If you look at the source code for complex solvers you'll notice that they are built around the simpler solvers.

Okay, thanks a lot for your notes. I've already worked through the first 20 pages of your suggested literature reference and it is very useful. It is perfect, that your reference also contains some information to the VOF-methode.

However, I think you are right. Beginning with basic source code and afterwards increasing the complexity to more challenging cases like the evaporatingFoam is a sound practise. Hope it will help to improve the general understanding.



Best regards from Germany
Philipp

[Phigo90]

I've worked through your suggested reference. It helps a lot to improve my overall insight of OpenFoam.

Now, I have several questions about the gammaEqn.H:
Are the following statemens correct:

1) phi is the volume flux at the faces(Unit: [m^3/s])?

2) The first term in phiGamma is div(v Gamma). In the case of the finite volume discretization I have to integrate this term over the volume of the cell. Hence, the unit of the term is [m^3 * m/s *1/m=m^3/s].
In the source Code, this term is calculated using the following Expression: fvc::flux(phi,gamma,gammaScheme).
Is the following statement correct: It can be multiplied with gamma leading to the discretized form of int(div(v Gamma)dV), because phi is already the volume flux?

3)In line 397 rhoPhi is calculated using the following source Code:
rhoPhi=phiGamma*(rho1-rho2)+phi(rho2).

To get this Expression, let us first consider the determination of the new density:
rho=gamma*(rho1-rho2)+rho(2)

Because I want to determine rhoPhi, I have to multiply the expression with phi (volume flux) yielding to
rhoPhi=gamma*phi*(rho1-rho2)+gamma*rho(2).

I recognize, that the variable which contains the second and third term of the evolution equation for the phase fraction gamma, is named phiGamma. Because int((d gamma)/(d t) dV)=gamma*phi, the evolution equation can be rewritten as:
gamma*phi=-...

The r.h.s. is defined as phiGamma in line 397. Why is the "-" in front of phiGamma in line 397 missing?

[massive_turbulence]

Originally Posted by Phigo90

I've worked through your suggested reference. It helps a lot to improve my overall insight of OpenFoam.

Now, I have several questions about the gammaEqn.H:
Are the following statemens correct:

1) phi is the volume flux at the faces(Unit: [m^3/s])?

2) The first term in phiGamma is div(v Gamma). In the case of the finite volume discretization I have to integrate this term over the volume of the cell. Hence, the unit of the term is [m^3 * m/s *1/m=m^3/s].
In the source Code, this term is calculated using the following Expression: fvc::flux(phi,gamma,gammaScheme).
Is the following statement correct: It can be multiplied with gamma leading to the discretized form of int(div(v Gamma)dV), because phi is already the volume flux?

3)In line 397 rhoPhi is calculated using the following source Code:
rhoPhi=phiGamma*(rho1-rho2)+phi(rho2).

To get this Expression, let us first consider the determination of the new density:
rho=gamma*(rho1-rho2)+rho(2)

Because I want to determine rhoPhi, I have to multiply the expression with phi (volume flux) yielding to
rhoPhi=gamma*phi*(rho1-rho2)+gamma*rho(2).

I recognize, that the variable which contains the second and third term of the evolution equation for the phase fraction gamma, is named phiGamma. Because int((d gamma)/(d t) dV)=gamma*phi, the evolution equation can be rewritten as:
gamma*phi=-...

The r.h.s. is defined as phiGamma in line 397. Why is the "-" in front of phiGamma in line 397 missing?

Where did you lookup gammaEqn.H line 397 because I cannot see it anywhere on the internet or on my harddrive.

How did you come to this conclusion exactly?

"the evolution equation can be rewritten as:
gamma*phi=-..."

[Phigo90]

Originally Posted by massive_turbulence

Where did you lookup gammaEqn.H line 397 because I cannot see it anywhere on the internet or on my harddrive.

Ah sry about that. I was talking about the interFoam solver section 3.2.3 of your suggested reference (Santiago Márquez Damián-FinalWork-Computational Fluid Dynamics, Description and utilization of interFoam multiphase solver).

Originally Posted by massive_turbulence

How did you come to this conclusion exactly?

"the evolution equation can be rewritten as:
gamma*phi=-..."

The Evolution equation (108) for the phase fraction in your reference is:

(d gamma)/(d t)+div(v gamma)+div(v_r*gamma*(1-gamma))=0

The second and third term are collected in phiGamma (line 381-394) and thus

int( (d gamma)/(d t) dV)=-phiGamma

The l.h.s is the volume flux at the face

But in line 397 rhoPhi is calculated using the following source Code:
rhoPhi=phiGamma*(rho1-rho2)+phi(rho2).

In my opinion it should be -phiGamma, because if we start from the density:
rho=gamma*(rho1-rho2)+rho(2), we should get the following expression:
rhoPhi=gamma*phi*(rho1-rho2)+gamma*rho(2).

And thus: int( (d gamma)/(d t) dV)=rhoPhi= -phiGamma*(rho1-rho2)+gamma*rho(2).

I hope you understand the issue. I think I should improve my English skills to explain my problems in a much better way

[massive_turbulence]

Originally Posted by Phigo90

Ah sry about that. I was talking about the interFoam solver section 3.2.3 of your suggested reference (Santiago Márquez Damián-FinalWork-Computational Fluid Dynamics, Description and utilization of interFoam multiphase solver).



The Evolution equation (108) for the phase fraction in your reference is:

(d gamma)/(d t)+div(v gamma)+div(v_r*gamma*(1-gamma))=0

The second and third term are collected in phiGamma (line 381-394) and thus

int( (d gamma)/(d t) dV)=-phiGamma

The l.h.s is the volume flux at the face

But in line 397 rhoPhi is calculated using the following source Code:
rhoPhi=phiGamma*(rho1-rho2)+phi(rho2).

In my opinion it should be -phiGamma, because if we start from the density:
rho=gamma*(rho1-rho2)+rho(2), we should get the following expression:

rhoPhi=gamma*phi*(rho1-rho2)+gamma*rho(2).

I hope you understand the issue. I think I should improve my English skills to explain my problems in a much better way

You said...

"To get this Expression, let us first consider the determination of the new density:
rho=gamma*(rho1-rho2)+rho(2)
Because I want to determine rhoPhi, I have to multiply the expression with phi (volume flux) yielding to
rhoPhi=gamma*phi*(rho1-rho2)+gamma*rho(2)."

Shouldn't it be this rhoPhi=gamma*phi*(rho1-rho2)+phi*rho(2)?

[Phigo90]

Originally Posted by massive_turbulence

You said...

"To get this Expression, let us first consider the determination of the new density:
rho=gamma*(rho1-rho2)+rho(2)
Because I want to determine rhoPhi, I have to multiply the expression with phi (volume flux) yielding to
rhoPhi=gamma*phi*(rho1-rho2)+gamma*rho(2)."

Shouldn't it be this rhoPhi=gamma*phi*(rho1-rho2)+phi*rho(2)?

I have revised my post with the hope of better describing my Problem.

[massive_turbulence]

Originally Posted by Phigo90

I have revised my post with the hope of better describing my Problem.

Looking at just the term,

int(gamma*phi*(rho1-rho2)) = -phiGamma*(rho1-rho2)

It's integration by parts, right?

[Phigo90]

Originally Posted by massive_turbulence

Looking at just the term,

int(gamma*phi*(rho1-rho2)) = -phiGamma*(rho1-rho2)

I still cannot see what you did to get a minus sign, are any of these variables special in some way where you take an integral and get a minus?

Okay, I try to explain it in another way.

Starting from the Evolution equation:
(d gamma)/(d t)+div(v gamma)+div(v_r*gamma*(1-gamma))=0.

Rewriting it to (substract the second and third term):
(d gamma)/(d t)=-(div(v gamma)+div(v_r*gamma*(1-gamma))).

if you integrate the l.h.s you will get int( (d gamma)/(d t) dV), which corresponds in my opinion to the physical meaning of gamma*phi.

Furthermore, "div(v gamma)+div(v_r*gamma*(1-gamma))" is defined as phiGamma (line 381). And thus
gamma*phi= -phiGamma.

But in line 397 it is still phiGamma without a minus, even though it is Gamma*phi in physical meaning which corresponds in my opinion to -phiGamma.

[massive_turbulence]

Originally Posted by Phigo90

Okay, I try to explain it in another way.

Starting from the Evolution equation:
(d gamma)/(d t)+div(v gamma)+div(v_r*gamma*(1-gamma))=0.

Rewriting it to (substract the second and third term):
(d gamma)/(d t)=-(div(v gamma)+div(v_r*gamma*(1-gamma))).

if you integrate the l.h.s you will get int( (d gamma)/(d t) dV), which corresponds in my opinion to the physical meaning of gamma*phi.

Furthermore, "div(v gamma)+div(v_r*gamma*(1-gamma))" is defined as phiGamma (line 381). And thus
gamma*phi= -phiGamma.

But in line 397 it is still phiGamma without a minus, even though it is Gamma*phi in physical meaning which corresponds in my opinion to -phiGamma.

Ok this was the part that makes it work "(d gamma)/(d t)=-(div(v gamma)+div(v_r*gamma*(1-gamma)))."

I agree, they might be wrong.

[santiagomarquezd]

Hello, line 397 is explained here:

https://onlinelibrary.wiley.com/doi/....1002/fld.3906

Regards!