Learning Forum

[namrata mishra]

Hii

I am using a UDF at the inlet to simulate wind flow inside the domain. Now, I need this wind profile at 30 degrees to the inlet. how can i specify angle in my boundary conditions without changing the udf. I am attaching some screenshots for reference.

Also, I chose velocity specification method normal to boundary. If I change it to magnitude and direction, I cant clearly understand what to specify in X, Y and Z directions.

 

[SRP]

Hi,

You need to make changes in the UDF itself to make flow at 30 degree or make an expression at the inlet corresponding to 30 degree.

Thank you.

[namrata mishra]

Ok. Can you please suggest me what changes do I need to make . My udf code is as follows:

#include "udf.h"

#define UREF 4.7/* ref. speed 3.0 m/s */

#define CMU 0.09 

#define H 12

#define u_star 0.52

#define delta 36

#define p_constant 0.4

 

 

DEFINE_PROFILE(velocity_profile, thread, position)

{

float x[ND_ND];

float y;

float u_in;

        face_t f;

 

 

begin_f_loop(f, thread)

{

F_CENTROID(x,f,thread);

y=x[1];

u_in = UREF*pow(y/H,0.3);

F_PROFILE(f,thread,position) = u_in;

}

end_f_loop(f, thread)

}

 

/*  profile for kinetic energy  */

 

 

DEFINE_PROFILE(k_profile, thread, position)

{

float x[ND_ND];

  face_t f;

        float y;

        float k;

 

        begin_f_loop(f, thread)

    {

      F_CENTROID(x,f,thread);

      y=x[1];

                k=(u_star*u_star/pow(CMU,0.5))*(1-(y/delta));

      F_PROFILE(f,thread,position)=k;

     

    }

  end_f_loop(f, thread)

}

 

/* profile for dissipation rate  */

 

 

DEFINE_PROFILE(dissip_profile, thread, position)

{

  float x[ND_ND];

  face_t f;

float y;

        float eps;

        

  begin_f_loop(f, thread)

    {

      F_CENTROID(x,f,thread);

y=x[1];

      eps=(pow(u_star,3)/(p_constant*y))*(1-(y/delta));

                F_PROFILE(f,thread,position)=eps;

    }

  end_f_loop(f,thread)

}

[Rob]

Change to "components" rather than magnitude normal to boundary. You then need two DEFINE_PROFILE(velocity_profile, thread, position) blocks for the two components. Hint, don't call them both "velocity_profile".