[p52sarup]

Hello

I would like to know how the fluid evolves within a system. Imagine an airbox with a constant spend of air, that airbox is gaining pressure with the passage of time, for example in 30 seconds it goes from P = 0 bar to P = 0.5 bar, and when it reaches this limit the spend becomes 0 in a instant

Could I represent this problem in Ansys?

[LuckyTran]

P = 0 bara does not exist in this universe. You have to try another number =).


The problem seems easily doable but you have a problem with your description. How do you determine when the stuff in the box is 5 bar? Because it is a pressure field and everywhere will be a different number.


Are you sure you want a constant velocity inlet and are you sure you don't wan to use a pressure inlet of 5 bar? This way when the contents reach the equilibrium pressure, the flow naturally stops.

[p52sarup]

Sorry for my description, I did it in a hurry. I will detail the problem better .

It is the airbox of a motorcycle. I want to do a simulation from the beginning to the end. We imagine a straight, at the beginning I have atmospheric pressure in the airbox and a motor spend mass flow that depends of RPM. As accelerated and the motorcycle change the pressure value goes up and the air consumption of the engine also increases. At the end of the straight I have the maximum pressure in the airbox and that's when I close the accelerator and the spend mass flow is 0, therefore a peak pressure is produced. Is there any way to simulate this whole process?

I have read about procedure UDF.

Could be varying the inlet pressure and the outflow in time, simultaneously?

Thank you

[LuckyTran]

You can turn the airflow on/off simply by changing the BC condition type or setting the massflow to 0. No need for complicated UDF.

I.e. you simulate 30 seconds with some massflow. Then you change the BC. Then you simulate another 30 seconds or whatever.

Only if you want a time-varying inlet pressure or time-varying massflow do you need to do a UDF. And you don't even need a UDF. You could still do it with a simple profile text file which contains a list of the values at each time.

[p52sarup]

Thanks a lot.

The pressure at the inlet varies with time, also the mass flow at the outlet.

I have incorporated this UDF to the inlet:

#include "udf.h"

DEFINE_PROFILE (unsteady_pressure, thread, position)
{
face_t f;
real t = CURRENT_TIME;

begin_f_loop (f, thread)
{
F_PROFILE (f, thread, position) = 101312 + 50 * t;
}
end_f_loop (f, thread)
}

But I do not understand very well how it works. As I understand it, the pressure will increase 101312 + 50 * t, with "t" being the time-step established in our set-up. it is right?

If this is correct, I will do the same in the outlet whit the flow.

the other possibility that you comment "profile text file", how is the procedure to do it?

thank