i'm having a rotating cylinder problem which is rotating along x -direction, which is dynamic mesh.i'm getting an error with CG motion,the error is"incorrect cg motion udf unsteady velocity. i'm attaching the program plz tell the necessaryu modifications in it. pls help me.... #include "udf.h" DEFINE_PROFILE(unsteady_velocity, thread, position) {

face_t f;

real t = CURRENT_TIME;

real w;

if (t<=0.1)

{

w = 52.3 * t;

begin_f_loop(f, thread)

{

F_PROFILE(f, thread, position) = w * t;

}

end_f_loop(f, thread)

}

else

{

w = 5.23;

begin_f_loop(f, thread)

{

F_PROFILE(f, thread, position)= w* t;

}

end_f_loop(f, thread)

} }

Hi, Can u please explain clearly a) the purpose of ur udf b) what ur are expecting from ur udf c) what is the logic behind this current udf

i did not understand the 52.3 value in ur udf this may help me in looking up through ur code.

can u please explain what exactly u what to do in ur problem

regards

Hi, or even u can look at this udf DEFINE_CG_MOTION this seems to be appropriate udf for ur problem.

This is what I understood from ur request. May this help u.

Regards

a cylinder is rotating in a rectagular tunnel with an angular velocity of 5 rad/sec (in steady case). In Unsteady case consider rotation of the cylinder for time =0.1 sec, theta=30 degees with linear profile.

hi, i have a problem.. on a plate...

plate will be in the tunnel.. at 15 degrees to x axis.

i need the UDF for steady state and also for un steady state where the plate moves for every 5 degrees ..

can i get the UDF program for steady and unsteady state.. please.. can anybody help me out...

Hi, Do you think that the plate is going to move by 5 degrees for every time step or each 5 degree is a saperate case

bye Ramesh

or u can also use outflow boundary conditions # Pressure far-field boundary conditions are used to model a free-stream compressible flow at infinity, with free-stream Mach number and static conditions specified. This boundary type is available only for compressible flows.

# Outflow boundary conditions are used to model flow exits where the details of the flow velocity and pressure are not known prior to solution of the flow problem. They are appropriate where the exit flow is close to a fully developed condition, as the outflow boundary condition assumes a zero normal gradient for all flow variables except pressure. They are not appropriate for compressible flow calculations.

sorry this is not for u i wrote in a wrong place

5 degrees for every time step....