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Axisymmetric swirl - angular velocity for UDF

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Old   November 21, 2011, 07:05
Default Axisymmetric swirl - angular velocity for UDF
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Tsaba Nagy
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hi everyone

i'm making a momentum field (tangential - like lorenz force in a magnetic case) to spin/rotate liquid metal in a cylindrical space. I need the angular velocity of every cell for my UDF. In 3D i can get it from velocity components and radius (radius is generated from coordinates).

but what is c_u(), c_v(), c_w() in axisymmetric swirl 2d. how can I get the angular velocity in rad/sec (or tangential velocity).

thanks
cheers
TS
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Old   July 27, 2012, 07:46
Default plz help me!!!
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Hi dear Tsaba Nagy.
I need to use 2D geometry for my solver and see axisymmetric swirl 2d in your comment!!!please tell me how can I do this for my project?
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Old   July 27, 2012, 07:50
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Tsaba Nagy
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please write, what you want since the post I developed a lot in these stuff. I hope I can help you
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Old   July 27, 2012, 09:29
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dear Tsaba Nagy.
I want to use 2Daxisymmetric for openFoam,and for this reason used makeAxialmesh and coolapse to make wedge type for boundary.
I make it,but my result after run is not correct and differrent with 3Dmodel.other friends tell me ,I must be use axisymmetric swirl 2d .....
if my work in modelling 2DAxisymetric is not correct please tell me???
Thanks a lot.
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Old   July 27, 2012, 09:43
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Tsaba Nagy
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the 2d axs. swirl solver is needed when there are swirling velocities too in the system you wanna model. In this case I'm not sure, that there is this type of velocity inside but worth to try.

forget this wedge cut shape model. for 3D draw the full media. for 2D the half of the meridional cut is enough - as you drew on the bottom of the first paper. set axis boundary condition here, others can be simple in/otlets, walls, etc.

if the inlet of the pressure is homogenous on the surface, the 2D is totally enoug to see what's happening inside.

did I understood well, what you want?
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Old   July 27, 2012, 10:13
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Thanks for your answer.
but i know my drew on the bottom of the first paper is correct!!!!but i dont know how can i do this???in openFoam 2D, conveted in 3D!!!
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Old   July 27, 2012, 10:35
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Tsaba Nagy
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I just work with FLUENT, so I can help justwith it now :/
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Old   June 30, 2015, 08:09
Default Tangential velocity in 2D axisymmetric flow with swirl
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Rob V
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I am currently working on the modelling of droplets in swirling, turbulent, pipe flow. I use a UDF to model the evaporation of the droplets, however, there is a problem with the particle and fluid velocities.

The fluid swirl-velocity is an output parameter of the calculations. However, I do not know how to use this parameter in Fluent. It is not the same as the cell velocity C_W(c,t), since that value is (null) in the calculations.

Thanks in advance!
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Old   July 2, 2015, 07:23
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Tsaba Nagy
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Maybe a too stupid/basic question, but are you pointing at the correct thread level for C_W, like


Thread *t_l = THREAD_SUB_THREAD(t,0);
real parameter =C_W(c,t_l);



It would be great to get more info about your case...


Cheers


Quote:
Originally Posted by Robb13 View Post
I am currently working on the modelling of droplets in swirling, turbulent, pipe flow. I use a UDF to model the evaporation of the droplets, however, there is a problem with the particle and fluid velocities.

The fluid swirl-velocity is an output parameter of the calculations. However, I do not know how to use this parameter in Fluent. It is not the same as the cell velocity C_W(c,t), since that value is (null) in the calculations.

Thanks in advance!
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Old   July 2, 2015, 07:53
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Rob V
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Currently, I am using it on the following way:

DEFINE_DPM_TIMESTEP(droplets_laws,p,dt_dpm)
{

... Other lines...

real W_C
cell_t c = P_CELL(p);
Thread *t = P_CELL_THREAD(p);
C_CENTROID(x,c,t);
W_C = C_W(c,t);

... Other lines...

}


However, I found out that C_WSWIRL(c,t) does return a value instead of C_W(c,t).


For my case, I model the evaporation of droplets using an inhouse-UDF.
In this routine, I use the difference between the particle velocity and the carrier phase velocity at particle position to calculate the particle Reynolds number.
For that purpose, the cell center velocity C_U(c,t) is interpolated to the particle position by means of the gradients C_DUDX(c,t) (with DUDZ, DYDZ and DWDZ zero by definition).
However, I found out that I also can use the inteprolated values from Fluent directly, so the problem is probably solved by making use of the following line:

W_C = p->cphase.V[3];
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