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simpleFoam: Influence of MRF region dimensions on simulation results

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Old   January 15, 2020, 04:05
Default simpleFoam: Influence of MRF region dimensions on simulation results
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Kmeti Rao
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Hi Dear Foamers,

I am using simpleFoam + MRF to study the behavior of the propeller in hover, which I have modeled. So far everything is fine as I had around 1.3 times the length of propeller as diameter and 0.4 times the length of propeller as thickness of the MRF region. As I wanted to study the performance of the propeller in hover condition surrounded by a duct, I have changed the dimensions of the MRF regions accordingly. With the new settings I did not achieved the convergence, and the simulation was not stable. Therefore to know the influence of MRF region I have carried out different tests with different settings to know the effect of MRF region dimension on simulation results.

The different effects observed are, when the propeller diameter and MRF region diameter are nearly same, the results were bad and had problems in convergence. When the MRF region is too narrow in terms of its height, the results were far from reality. The same phenomenon was observed when the propeller is close to the MRF inlet.

To avoid all the above mentioned problems I have decided to use a bigger MRF region, in which I have placed the duct inside the MRF region (by defining it as non rotating patch). This settings have made the situation even worse, and I have had lot of uncertainties, as explained in the following thread Divergence of ducted propeller simulation using MRF simpleFoam.

MRFProperties:

Quote:

MRF1
{

cellZone rotor;
active yes;

// Fixed patches (by default they 'move' with the MRF zone)
nonRotatingPatches (AMI1 AMI2 AMI3 AMI4 AMI5 AMI6 duct);

origin (0 0 0);
axis (0 0 1);
omega 616;
}
A small hint from the community would be of a great help, thank you all in advance.

Kmeti Rao
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Old   January 16, 2020, 04:26
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Kmeti Rao
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Dear Foamers,

I have almost gone through the whole forum to find if there are any chance of getting a small hint to carry the work further, to my surprise many have asked this question before, but there are no answers! I have gone through not only in OpenFOAM forum but also in ansys forum. So many people are facing the problem while simulating the propeller inside the duct. If possible lets try to find the answer together.

Thank you all once again in advance
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Old   January 16, 2020, 04:41
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Kmeti Rao
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For future readers to make it easy these are the threads which deals with ducted propellers, if you have luck you might get answer in future :P

Ducted propeller MRF issue

Ducted propeller- Wall/Interface?

meshing ducted propeller

Streamline simulation for Ducted Propeller

simulation of water flow though a ducted propeller

Divergence of ducted propeller simulation using MRF simpleFoam

Ducted propellers
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Old   February 5, 2020, 02:48
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Kmeti Rao
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Dear Foamers,

It's been two weeks! Any input from the experts?

The case set up is presented in following thread Divergence of ducted propeller simulation using MRF simpleFoam

Thank you
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convergance, ducted fan, mrf simplefoam, openfaom-6, propeller

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