# blood flow - aneurysm

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 March 21, 2013, 03:57 blood flow - aneurysm #1 Senior Member   stephane sanchi Join Date: Mar 2009 Posts: 312 Rep Power: 11 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.

 March 21, 2013, 04:23 #2 Senior Member     Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,266 Rep Power: 23 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 __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer.

 March 21, 2013, 04:30 #3 Senior Member   stephane sanchi Join Date: Mar 2009 Posts: 312 Rep Power: 11 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. Best regards, Stephane.

 March 21, 2013, 04:43 #4 Senior Member     Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,266 Rep Power: 23 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. __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer.

 March 21, 2013, 06:24 #5 Senior Member   stephane sanchi Join Date: Mar 2009 Posts: 312 Rep Power: 11 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.

 March 21, 2013, 06:44 #6 Senior Member     Jose Rey Join Date: Oct 2012 Posts: 131 Rep Power: 11 Blood is non-newtonian also. Does it matter at this scale and conditions? chaitanyaarige likes this.

 March 21, 2013, 07:06 #7 Senior Member   stephane sanchi Join Date: Mar 2009 Posts: 312 Rep Power: 11 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. Regards, Stephane.

March 21, 2013, 07:22
#8
Senior Member

Gerhard Holzinger
Join Date: Feb 2012
Location: Austria
Posts: 211
Rep Power: 19
Quote:
 Originally Posted by openfoam_user 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.

 March 21, 2013, 07:55 #9 Senior Member   stephane sanchi Join Date: Mar 2009 Posts: 312 Rep Power: 11 Hi Gerhard,thanks for your useful information. Best regards, Stephane.

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