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UDF for time dependent angular velocity calculation

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Old   July 1, 2014, 01:03
Default UDF for time dependent angular velocity calculation
  #1
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shashank mishra
Join Date: Sep 2011
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Hi,
I am trying to use dynamic meshing for 2D wind turbine simulation and generate rpm on the basis of inlet velocity using udf.

This is the code I wrote

#include"udf.h"
real w_prev= 0.0;
DEFINE_CG_MOTION(turbine, dt,vel,omega,time,dtime)
{

Thread *t;
face_t f;
real NV_VEC(A);
real force,torque,x[ND_ND], dw;
NV_S(vel,=,0);
NV_S(omega,=,0);

/* Get the thread pointer for which this motion is defined */
t= DT_THREAD(dt);
/* Compute pressure force of body by looping through all faces */
force = 0;
torque= 0;
begin_f_loop(f,t)
{
F_AREA(A,f,t);
F_CENTROID(x,f,t);
torque+= x[1] * (F_P(f,t)* NV_MAG(A);
}
end_f_loop(f,t)

/* Compute change in angular velocity */
dw= dtime* torque/ 50.00;
w_prev= w_prev + dw;

Message ("time = %f , z_omega= %f,torque = %f\n", time, w_prev, torque);
/* Set Z Component of Angular velocity */
omega[2]= w_prev;

I know the code is wrong since I need to take the vector cross product of force with radius vector but I dont have any idea how to do that so I made is simple and tried to run this with this wrong code.

Anyone have any comment on how to get what I wish to simulate

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Old   October 24, 2016, 03:34
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Klxing
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There seems to be an marcon "Compute-force-and-momentum" which can be used to compute the momentum
but i am not quite sure . u can do some research about it
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Old   October 24, 2016, 04:43
Question UDF for inlet temperature
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mm
Join Date: May 2016
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mmunige is an unknown quantity at this point
Dear all

I have following UDF for inlet temperature, untill 1300s it takes correct values according to equation, but after 1300s values are higher and not accorrding to equation, like at 1301s it should have value of 405C but in simulation inlet temperature is 621C. I could not find the error in my UDF after lot of try. please check this and guide me. Thank you.
#include"udf.h"

DEFINE_PROFILE(inlet_temperature,thread,position )

{

face_t f;

begin_f_loop(f,thread)

{

real t = RP_Get_Real("flow-time");

if (t <=1300.0 )

{

F_PROFILE(f,thread,position) = 379.13 + 0.0005*t;

}

else if (1300.0 < t && t <= 1500.0 )

{

F_PROFILE(f,thread,position)= -1.04289036878969*pow(10,-10)*pow(t,6.0)+ 8.86126436853789*pow(10,-7)*pow(t,5.0)-3.13621260398811*pow(10,-3)*pow(t,4.0)+5.91804640375908*pow(t,3.0)-6.27969461279651*pow(10,3)*pow(t,2.0)+ 3.55273415252714*pow(10,6)*t - 8.37223405676245*pow(10,8);
}
else
{

F_PROFILE(f,thread,position) = -9.51538261322402*pow(10,-23)*pow(t,6) + 8.26192751387975*pow(10,-18)*pow(t,5)-2.85237398505875*pow(10,-13)*pow(t,4)+4.97518353700886*pow(10,-9)*pow(t,3)-4.58733775886876*pow(10,-5)*pow(t,2)+ 2.10251137071757*pow(10,-1)*t +3.57252192344954*pow(10,2);

}

}

end_f_loop(f,thread)

}
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