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Old   March 21, 2013, 03:57
Default blood flow - aneurysm
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stephane sanchi
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Hi OF-users,

I'd like to model the blood flow in the aneurysm.

Blood characteristics are:
- density: 1080 kg/m3
- kinematic viscosity: 3.7037e-06 m2/s

Which solver do you recommend for such a computation ?

I want to start with a steady-state solver.

Best regards,
Stephane.
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Old   March 21, 2013, 04:23
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Anton Kidess
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You specified the viscosity as a constant, thus you can use simpleFoam. In the future, you can easily find the answer to such a question here: http://www.openfoam.com/features/standard-solvers.php
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Old   March 21, 2013, 04:30
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stephane sanchi
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Hi Anton,

OK.
But with the simpleFoam solver you don't need the density. Does it mean that density is equal to 1 or not ?
You only set the kinematic viscosity.

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Stephane.
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Old   March 21, 2013, 04:43
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Anton Kidess
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If the density is constant, the equations can be rewritten such as that you do not have to explicitly specify it. Implicitly it comes back in the use of kinematic instead of dynamic viscosity. You can find details in any fluid mechanics textbook.
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Old   March 21, 2013, 06:24
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Hi Anton,

Now it works. I put laminar as RASModel in the RASProperties file.

Previously I had kEpsilon as RASModel with turbulence off.

So it means that a laminar computation is not equal to a turbulent computation with turbulence off !!!

Best regards,
Stephane.
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Old   March 21, 2013, 06:44
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Jose Rey
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Blood is non-newtonian also. Does it matter at this scale and conditions?
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Old   March 21, 2013, 07:06
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Hi,

I think you can assume blood as a Newtonian fluid in (large) arteries.
But in small capillaries it must be considered as non-Newtonian fluid.

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Stephane.
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Old   March 21, 2013, 07:22
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Quote:
Originally Posted by openfoam_user View Post
Hi Anton,

Now it works. I put laminar as RASModel in the RASProperties file.

Previously I had kEpsilon as RASModel with turbulence off.

So it means that a laminar computation is not equal to a turbulent computation with turbulence off !!!

Best regards,
Stephane.
IF you look at the source code of simpleFoam, you will find, that simpleFoam always uses a RAS turbulence model.

This are some lines of simpleFoam.C

Code:
Application
    simpleFoam

Description
    Steady-state solver for incompressible, turbulent flow

\*---------------------------------------------------------------------------*/

#include "fvCFD.H"
#include "singlePhaseTransportModel.H"
#include "RASModel.H"
#include "simpleControl.H"
#include "IObasicSourceList.H"
You see, the header RASModel.H is included instead of turbulenceModel.H. E.g. compare the first lines of code of simpleFoam with the first lines of pimpleFoam.

The file createFields.H of simpleFoam contains the following lines:

Code:
singlePhaseTransportModel laminarTransport(U, phi);

    autoPtr<incompressible::RASModel> turbulence
    (
        incompressible::RASModel::New(U, phi, laminarTransport)
    );
A RAS turbulence model is create/ used in any case, so the switch turbulence of turbulenceProperties is inactive.
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Old   March 21, 2013, 07:55
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Hi Gerhard,thanks for your useful information.

Best regards,
Stephane.
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