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-   -   How To simulate a pulsating flow in OpenFOAM (http://www.cfd-online.com/Forums/openfoam-solving/58655-how-simulate-pulsating-flow-openfoam.html)

fw407 July 15, 2008 15:22

Hi everyone, I am trying to
 
Hi everyone,

I am trying to modify icoFoam so that it can simulate a pulsating flow in a straight flexible pipe. the flow velocity at the inlet is uniformly distributed but the velocity magnitude changs with time:

U = U_0 + U_A*sin(wt)

I have noticed the "timeVaryingUniformFixedValueFvPatchField " may be what I want, but it needs to read the data from a data file. Actually I prefer to implement it in the code somthing like:

U.boundaryField()[patchI] == U_0 + U_A * sin (wt)

and read the "w", "U_0" and "U_A" in a dictionary.

So far I haven't got an idea of how to do that, Could anyone give me some hints?

Kind regards

feng

mathieu July 15, 2008 16:12

Hi ! Take a look at the osc
 
Hi !

Take a look at the oscillatingFixedValueFvPatchField, I think it is exactly what you need.

Mathieu

ngj July 15, 2008 16:28

Hi Feng As a start, assume
 
Hi Feng

As a start, assume you know w, U_0 and U_A, then simply do this, which you have already done:

U.boundaryField()[patchI] == U_0 + U_A * sin (wt);

and add the line:

U.correctBoundaryConditions();

It should to the trick.

With respect to be reading from a dictionary, look for instance at

OpenFOAM/OpenFOAM-1.4.1/applications/solvers/DNSandLES/dnsFoam

and search for IOdictionary.

Have fun,

Niels

fw407 July 16, 2008 06:23

Hi Mathieu, Thanks for your
 
Hi Mathieu,

Thanks for your help, I really appreciate it. oscillatingFixedValueFvPatchField is working fine with me.

Kind regards

feng

fw407 July 16, 2008 06:27

Hi Niels, I really apprecia
 
Hi Niels,

I really appreciate your help. I will try more complex functions with your method.

Kind regards

feng

woody August 13, 2008 04:57

Hi, I also work on pulsatil
 
Hi,

I also work on pulsatile flows. I am especially interested in heat transfer effects, that occur in turbulent problems containing flow reversal.

So far I tried to simulate my very long (l/D=120) channel with a constant wall temperature, pulsating velocity and oscillatory temperature BC at the inlet. I introduced a special turbulence Model (Wang & Zhang: "Numerical analysis of heat transfer in pulsating turbulent flow in a pipe", Heat and Mass Transfer, 2005) containing wallfunctions. As compressible fluids should be considered, the rhoTurbFoam solver seemed to be the best fitting choice.

When run my computations, the temperature cant follow the backflow conditions, and is increased non-physical.

Scanning the tutorials, I found some other remarks, that backflow causes instabilities and some suggestions, which are not commented to have been worked out or taken to be valid.

Is anybody out there who handled similar problems and has some information, hints etc.???

Thanks Tobias

woody August 13, 2008 05:08

Sorry, I scanned the forum
 
Sorry,

I scanned the forum ... and not the tutorial...

;-)

Tobias


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