[ash_n]

Hey all!

So I am modelling a simple Laminar 2D Pipe flow in Fluent, (which I am new to btw). So, once I solve for the transient case for a certain timesteps and I get more or less a steady state solution, I want to introduce a pressure perturbation at the inlet and wanna gauge the response of the fluid. How can I go about doing this in Fluent?

Kindly suggest a simple method for this.

Regards.

[rohitkjohn]

Hello,

If you want to introduce a perturbation by changing the boundary condition, I would suggest you use a UDF. The following is a code which you can save as a .c file and compile in FLUENT


/* the following UDF imposes a value of pressure p0 at the required boundary before time t1. Once t1 is crossed the this a perturbation is introduced in the form
of an increased pressure, p1, at the boundary. This is done using an if-else condition
*/

#include "udf.h"

DEFINE_PROFILE(unsteady_pressure, thread, position)
{
face_t f;
real t = CURRENT_TIME;
real t1 = 0.1; /*The time after which you want to add the perturbation*/
real p0 = 200; /*This is the initial pressure you impose at the boundary*/
real p1 = 210; /*This the perturbed value of pressure*/

begin_f_loop(f, thread)
{
if(t<t1)
{
F_PROFILE(f, thread, position) = p0;
}

else
{
F_PROFILE(f, thread, position) = p1;

}
}
end_f_loop(f, thread)
}

[rohitkjohn]

you may search online how to add a UDF to FLUENT