Hello Everybody,

I am simulating compressible flow in 90 degree bend with an extension tube at the bend exit. I need to use total pressure at the inlet and mass flow rate at the exit. I have changed the pressure outlet to mass flow outlet boundary by giving a target mass flow rate through text mode. I am not getting the desired mass flow rate(0.045 kg/s) though all the residuals have come down to 10e-3 and there is no mass imbalance(0.36 kg/s at the inlet and exit). I have tried both target mass flow boundary available in Ver 6.1.18 and scheme file for implementing mass flow outlet. But, in both the cases it's not converged to the desired mass flow rate (0.045 kg/s).

Can anybody please help me in setting up the mass flow outlet boundary? Please help me in setting up the parameters to make the iteration for target mass flow rate algorithm faster?

Thanking you in advance.

Regards Nitin

Just a query....

Does the flow go sonic through any part of the flowfield?

nandu

Yes it goes above sonic at some location. But it's neither at the inlet (Total Pres BC) nor at the exit where i am defining the target mass flow rate.

Thanks for your help in advance.

Nitin

Sounds like you have a shoked flow, that would fix the mass-flow.

Thanks Jonas. Do you think that there would be convergence problem (getting the desired mass flow rate) of the target mass flow rate algorithm due to reverse flow at the exit? I can remember that somebody pointed out the convergence is very slow but it works.

Therefore, i would be happy if anybody gives some guideline on setting up the parameters of mass flow algorithm.

Regards Nitin

Thanks Jonas. Do you think that there would be convergence problem (getting the desired mass flow rate) of the target mass flow rate algorithm due to reverse flow at the exit? I can remember that somebody pointed out the convergence is very slow but it works.

Therefore, i would be happy if anybody gives some guideline on setting up the parameters of mass flow algorithm.

Regards Nitin

If you have a choked sonic throat inside your domain then the target-mass-flow outlet BC will not work - it will just continue to reduce the outlet pressure more and more but it will be impossible to reach the target mass-flow. The choked sonic throat puts a physical limit on the mass-flow which you have to accept. You can't change the physics by using a different boundary condition.

[asal]

Hello all!

I need to simulate a case that I need to specify volume flow out (l/s). I tried pressure outlet and set a negative pressure outlet both with and without target mass flow, but it is difficult to obtain desired volume flow and it needs several try and errors.
This is the same for volume flow inlet.
Any solution to this?

Thanks.

[yousef13]

hello
-Is a book or an article about the history of the target conservation of mass in the exit?
-To activate Run program targeting the mass flow rate increases?
-There a way to solve the program runs quickly increase(itration)?
thank you

[yousef13]

Hello
I want find a history of mass flow control in outlet boundary, such as an article or a book .is method convergence speed increases ?
Is there a similar method for accelerating convergence?
please Help me to find this