Could we change the dynamicMeshDict in constant while running simulations

chandra shekhar pant · October 31, 2019, 03:33

Dear Foamers,

I am running a similar case that is described in propeller tutorial. In this case the fluid inlet velocity is in -ve y direction and the axis of rotation is +ve direction, is this correct to start with ?
I had started my simulations with the same set of directions and it had ran for about a week, but I found that the vortex are not being shed, is it because of this direction issue?
Also suppose if I found that its incorrect and intent to restart the simulations, will it be possible if I change the axis of rotation to -ve direction and re-run from the latest time step?
Any help is highly welcomed, it will save my enormous amount of time.

Thanks !

Krao · October 31, 2019, 04:55

Hi Chandrashekar, If you think it makes sense to continue the simulation from the latestTime step, of course you can change the entries of dynamicMeshDict, and run from the latestTime step.

Quote:

I am running a similar case that is described in propeller tutorial. In this case the fluid inlet velocity is in -ve y direction and the axis of rotation is +ve direction, is this correct to start with ?

Cross check these in paraview, flow should be in the direction from inlet to outlet, if your direction of inlet is in -y axis then it should not be a problem. Positive and negative values of rotation velocity indicates, whether it is counterclockwise or clockwise motion. If you have any doubts in these, crosscheck with paraview after few initial iterations.

Quote:

Could we change the dynamicMeshDict in constant while running simulations

From you title one thing I can suggest, you can vary BCs and system while running the simulation, but not the files inside constant directory. As the name suggests, constant remains constant during simulation. But always you can stop at writeNow, edit and restart from the latestTime.

K. Rao

chandra shekhar pant · October 31, 2019, 06:59

Hello K Rao,

Many thanks for the reply and help. But I am still wondering that if the inlet velocity is in -ve direction then it will force the propeller to rotate in clockwise direction (from the right hand thumb rule), now if I am having the impose rotational axis to be +ve which is counter-clock wise direction (which I assume according to the convention). Then don't you think that there will be some problem ? Although I have a created a similar set-up that of the tutorial, -ve v inlet velocity, domain extending in -ve y axis from inlet at 10 and outlet at -90, exactly similar to that of the tutorial case. But yet I am not able to see the vortex sheding in this case. Just become a bit anxious that, is this what is creating an issue. Hope you understand that a considerable time has already been spend from my side on this case.

I am referring to the propeller tutorial, what you think about this case?

Thanks a lot!

October 31, 2019, 03:33	Could we change the dynamicMeshDict in constant while running simulations	#1
chandra shekhar pant Senior Member chandra shekhar pant Join Date: Oct 2010 Posts: 220 Rep Power: 16	Dear Foamers, I am running a similar case that is described in propeller tutorial. In this case the fluid inlet velocity is in -ve y direction and the axis of rotation is +ve direction, is this correct to start with ? I had started my simulations with the same set of directions and it had ran for about a week, but I found that the vortex are not being shed, is it because of this direction issue? Also suppose if I found that its incorrect and intent to restart the simulations, will it be possible if I change the axis of rotation to -ve direction and re-run from the latest time step? Any help is highly welcomed, it will save my enormous amount of time. Thanks !

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October 31, 2019, 06:59		#3
chandra shekhar pant Senior Member chandra shekhar pant Join Date: Oct 2010 Posts: 220 Rep Power: 16	Hello K Rao, Many thanks for the reply and help. But I am still wondering that if the inlet velocity is in -ve direction then it will force the propeller to rotate in clockwise direction (from the right hand thumb rule), now if I am having the impose rotational axis to be +ve which is counter-clock wise direction (which I assume according to the convention). Then don't you think that there will be some problem ? Although I have a created a similar set-up that of the tutorial, -ve v inlet velocity, domain extending in -ve y axis from inlet at 10 and outlet at -90, exactly similar to that of the tutorial case. But yet I am not able to see the vortex sheding in this case. Just become a bit anxious that, is this what is creating an issue. Hope you understand that a considerable time has already been spend from my side on this case. I am referring to the propeller tutorial, what you think about this case? Thanks a lot!