[alqayssi69]

HI member
Depending in my experience the using of Giesekus model reveal divergence result with large shear rate value and this is one of drawback in using this model. I really search in the source of divergence and try to find suitable approach .

I would like to know detail information about your geometry so I can more helpful in this issue.

you are free to message me on my G Mail .
engineer.alqayssi@gmail.com

Best Regard

[Julya_Shmit]

Thanks for your reply, Ahmed.

I am very glad to know that anybody tries to help me because I am at a nonplus.
What detail information about geometry do you need?

I have already specified geometry, model's parameters and boundary conditions in previous reply (file Geometry.jpg).

[alimea]

Dear jovani
Thanks for developping OF for viscoelastic fluids.
I'm a new foamer.
I want to solve "free convection flow and heat transfer of viscoelastic fluid by Buossinesq approximation"
Could you plz help me how to do that?

[pippo2013]

Originally Posted by Hiroshiman

Hi every one,
I'm working on multiphasic flows of viscoelastic fluids. I used the interDyMFoam and viscoelasticFluidFoam from of OE 3.1 to create a interViscoDyMFoam, using the work here.
However, the viscosity from the constant/transportProperties is still used by the twoPhaseMixture operation :

    
     nuModel1_
     (
    viscosityModel::New
         (
             "nu1",
             subDict(phase1Name_),
             U,
             phi
         )
     ),
     nuModel2_
     ( 
        viscosityModel::New
         ( 
            "nu2",
             subDict(phase2Name_),
             U,
             phi
         )
     ),

How can I replace these values read in a dictionnary by values computed from the flow field ? Or maybe there is a simpler approach..


edit:
actually I'd only need to read the viscoelascticProperties from the twoPhaseMixture files. However, the definitions are quite different from reading from the transportProperties files as usual. How could I, for example, read etap1 from constant/viscoelascticProperties in twoPhaseMixture.C ?


Best regards,
Florian

Hi everyone!
I am interested in applying viscoelasticFluidFoam to a dynamic mesh.
Frorian, have you succeded in developing interViscoDyMFoam? The code (cited in the quoted post) is no more linked. Could you please make it available?
Any other help in combining viscoelasticFluidFoam and interDyMFoam would be highly appreciated!

Thank you!!

[tdof]

Hi, I've got a question concerning the calculated stresses of the Leonov model. Since OF uses kinematic viscosity and kinematic pressure, are the displayed stresses from tau and sigma also divided by rho?

[bfzah]

Hello
How can I form a vortex in a square-shaped channel?
Or how can I see vortices?
In all the papers, a vortex pair is seen at the corners of the channel with the Giesekus model.
How can this be modeled with open foam?
what is the properties flow ?
B.C ?

please help me?

my Email: farhadhoseinbor@gmail.com
Telegram id: @bfzah

[adambarfi]

Originally Posted by bfzah

Hello
How can I form a vortex in a square-shaped channel?
Or how can I see vortices?
In all the papers, a vortex pair is seen at the corners of the channel with the Giesekus model.
How can this be modeled with open foam?
what is the properties flow ?
B.C ?

please help me?

my Email: farhadhoseinbor@gmail.com
Telegram id: @bfzah

Greetings,

First of all, welcome to CFD-online.

Let me explain a little bit when some vortices are formed in fully developed laminar viscoelastic flow. Having corner in the cross section of a channel in fully developed viscoelstic fluid flow results in a pair of elastic vortices. So, in a channel with square cross section we can see eight elastic vortices, very similar to the vortices in the fully developed turbulent flow of a Newtonian fluid in the same geometry. The intensity of these eight vortices in fully developed laminar viscoelastic flow is around 3 percent while in fully developed turbulent flow of a Newtonian fluid it is around 30%.

I cannot remember if the Weissenberg number may affect the intensity of these vortices, but I certainly know that non-newtonian model such as Oldroyd-B, power-law, etc cannot simulate these vortices.

the boundary conditions are simple. An uniform velocity intet, pressure outlet, and non-slip boundary condition for the walls. The flow should reach the fully developed state in the channel. Just use the viscoelastic properties provided by Jovani in the tutorial case.

Have fun
Mostafa

[bfzah]

Originally Posted by adambarfi

Greetings,

First of all, welcome to CFD-online.

Let me explain a little bit when some vortices are formed in fully developed laminar viscoelastic flow. Having corner in the cross section of a channel in fully developed viscoelstic fluid flow results in a pair of elastic vortices. So, in a channel with square cross section we can see eight elastic vortices, very similar to the vortices in the fully developed turbulent flow of a Newtonian fluid in the same geometry. The intensity of these eight vortices in fully developed laminar viscoelastic flow is around 3 percent while in fully developed turbulent flow of a Newtonian fluid it is around 30%.

I cannot remember if the Weissenberg number may affect the intensity of these vortices, but I certainly know that non-newtonian model such as Oldroyd-B, power-law, etc cannot simulate these vortices.

the boundary conditions are simple. An uniform velocity intet, pressure outlet, and non-slip boundary condition for the walls. The flow should reach the fully developed state in the channel. Just use the viscoelastic properties provided by Jovani in the tutorial case.

Have fun
Mostafa

tnx my dear friend .
i'm very happy that answer my question's.
But I can not do it.
All the details that the rest of the researchers did in their previous work, I did. I do not know why I can not see the vortex

[bfzah]

this is my file.

[adambarfi]

Originally Posted by bfzah

this is my file.

Your boundary conditions seems ok to me as well as the fluid properties. What is the Reynolds number? How long is the length of your channel? Does the flow get fully developed though it?
How do you visualize the secondary flows?

[bfzah]

Re=rho*u*D/etha
rho=1000, u=0.2, D=0.02, etha=etha(s)+etha(p)=4

Assume a long channel, but I'm not sure that the flow has been developed!

[adambarfi]

Originally Posted by bfzah

Re=rho*u*D/etha
rho=1000, u=0.2, D=0.02, etha=etha(s)+etha(p)=4

Assume a long channel, but I'm not sure that the flow has been developed!

So Re=1; creeping flow! I think that's a little tricky.

Did u assume the flow is steady state? If yes, it is not a concern how the outlet velocity is changing during your simulations. Just let it solve the geometry completely and then draw the secondary flows on a surface at the fully developed section of your duct (NOT at the outlet surface).

On the other hand, plotting the secondary flows is tricky, too. You can google it how to draw secondary flows in paraFoam.

Good luck!

[bfzah]

Originally Posted by adambarfi

So Re=1; creeping flow! I think that's a little tricky.

Did u assume the flow is steady state? If yes, it is not a concern how the outlet velocity is changing during your simulations. Just let it solve the geometry completely and then draw the secondary flows on a surface at the fully developed section of your duct (NOT at the outlet surface).

On the other hand, plotting the secondary flows is tricky, too. You can google it how to draw secondary flows in paraFoam.

Good luck!

yes flow is steady state.
thanx

[tdof]

Hi, I've got a question about the PISO algorithm used in viscoelasticFluidFoam. The official statement in the OF documentation is that it does not use underrelaxation, but the example cases all implement relaxation factors. I therefore assume that the PISO algorithm has been modified to allow their usage, but is a description available somewhere describing this exactly? Edit: I've found it in the source code, but is there a diagram or other explanation available?

Also, does the solver use the complete Navier Stokes equations or only Stokes?

[hjasak]

The solver solves the Navier-Stokes equations

I do not think you need an entire book just for the fact that PISO under-relaxaes the momentum equation to improve stability.

In any case, we are moving to coupled solvers - see recent work from Prof Nobrega.

Hrv

[tdof]

Great, thank you for your reply Prof. Jasak.

[bfzah]

How to create a transient fluid flow in the channel?
What conditions are required in a viscoelasticfluidfoam solver to generate a transient fluid flow?

[alimea]

Originally Posted by bfzah

How to create a transient fluid flow in the channel?
What conditions are required in a viscoelasticfluidfoam solver to generate a transient fluid flow?

Hi farhad
It's like what they do in tutorials. what do you mean about "conditions"?

[bfzah]

Originally Posted by alimea

Hi farhad
It's like what they do in tutorials. what do you mean about "conditions"?

boundary condition for walls and symmetry palne in square channel and (tau,u,p) define in PTT-EXP single mode!

[alimea]

Hi foamers

I'm working with viscoelasticfluidfoam. We know that this solver is written based on PISO algorithm and this algorithm doesn't have relaxation factor. So why did they use relaxation factors in many examples of tutorials?

What should I do?
I'v solved some problems with relaxation factors (e.g. 0.3 , 0.5) and now some of my friends tell me that they are wrong!

please help me if you are confident about this issue.