Oscillatory flow in a channel

yms

Hello everybody,

I am trying now to solve a simplified thermoacoustic problem using Fluent6.1. It is simply an oscillatory flow problem inside a channel,

The channel is: 1 m long and 0.08 m width

with pressure inlet B.C.: p= 2000*cos(4*t)+patm and pressure outlet BC: p= -2000*cos(4*t)+patm initial conditions: p=-4000*x+patm (patm=1.01e5 pa) and zero velocity.

time:0-->15.71s (period of one cycle is 1.571 s).

properties of the fluid: kinematic viscosity=2.5e-4 m^2/s( so i am using a density of 1000 kg/m^3 and dynamic viscosity of 0.25 Pa.s)

I used a udf to specify the inlet and outlet transient boundry conditions, and custom function for the initial pressure (because it varies with x).

I am using the coupled solver, but i am getting a strange solution where the x-velocity is a function of y and x while it should be function of y only. The solution gives high velocity at the inlet and then it decreases. I suspect that there is a mistake in specifying the inlet condition, because even when i solve for steady state case, the velocity at the inlet is high and then it becomes almost constant and function of y only.

Is there any suggestion.

Your help is so much appreciated.

Best regards, YMS