inlet manifold
 

Hello friends,

I am simulating diesel engine inlet manifold.
For this i am using velocity inlet for inlets and pressure outlets for outlets.
For transient boundary conditions i am using transient profiles.In this there are negative pressures.In operation conditions i changed pressure to zero.To use absolute pressures.

But the problem is one of the outlet is changing to inlet and revers flows are occurring on the so many faces of outlets.When i am using gauge pressures the outlet remaining outlet.

So please give me suggestions to overcome this problem.

please....

Thanks in advance.

hard to imagine what u trying to say. can u post picture with explaination?

Setting the pressure operating condition to zero is a very bad move, the way fluent solver sees it. Try setting it back to atmospheric. I'm sure you should be able to overcome the problem.

Thanks for u r replay,

I changed the operating pressure to 101325pas, and changed the operating pressures in to guage pressures.But still iam getting the same results.

Means the outlet is becoming in to inlet and reverse flows occurring on so many boundary faces.

Iam unable to find for what resons these reverse flows are occurening.
and why the outlet is changing in to inlet.

please give me some idea for what resones these are occurring.

thanks in advance.

your outlet-BC cannot switch to inlet-BC without you have specified it.
Check your massfow at inlet and outlet, the imbalance should be 0, and the massflow at your outlet should be negative.
If not, then you have a problem
Reversed flow can occure (for instance vortex accross the outlet)

Thanks for u r quick replay max,

I check the mass flow the imbalance it is 0. But one of the outlet have the positive value.

In the time of running solution reverse flows are occurring on outlets.So I think due to this the outlet is changing in to inlet is am correct.

so how can i avoid this problem.Means what the reasons for my problem am not getting.

Please give me suggestions on this matter.

thanks in advance.

If your mass imbalance is 0, but one of your outlet has negative value, it is weird.
How is the pressure distribution in your model? (realistic?)
What kind of BC did you set at your inlet?

pressure distribution is realistic and velocity inlet is the BC.

post a picture with your pressure ditribution and also velocity distribution

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Pressure and velocity distributons

Your geometry seems to be symetrical, if your BC are alson symetrical, you can split your domain and compute one half.
Your outles are quite close to T-junction. For sure they are in a recirculation zone.
I would extend the outlets.

Send me the geometry and BC... I'll try to make a parallel calculation to your...

Give me u r mail id i will send geometry and BC to u r mail.

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ejector
 

renu, Judging from the pictures, the right hand outlet is nearly opposite the inlet, whereas the left one is offside. Looks to me that the left hand outlet is actually an ejector and I would guess that this is the one with the reverse flow.

Thanku for u r replay,

I didn't understand how to overcome this problem.Can u give me any suggestions. Actually at outlets there are suction pressures also.I think thats why these reverse flows are occurring.

Is the suction pressures are reasons for the reverse flows then how would i overcome this problem.