[praroopjain]

Actually I am simulating the air flow from a nozzle like structure and I get these results. (shown in screen shot)
the velocity at the end point is nearly 1k kmph if the velocity of air at the inlet is 4 kmph. Is there any method to reduce this velocity.

[MB72]

Originally Posted by praroopjain

Actually I am simulating the air flow from a nozzle like structure and I get these results. (shown in screen shot)
the velocity at the end point is nearly 1k kmph if the velocity of air at the inlet is 4 kmph. Is there any method to reduce this velocity.

If you are allowed to change the nozzle design geometry, and the solution you are obtaining sounds good (=converge) (I don't have enough data to judge), the easiest way is to enlarge the nozzle outlet.
Another way is to have a powerful energy dissipation inside the nozzle (something like a very dissipating porous media = very "dense" filter. Porous media is very quick to model in almost all CFD commercial code).

However let me tell you, that if the intake velocity is just 4 km/h and the outlet is 1000 km/h (if I undrstood well) there is for sure some convergence problem, if you are working at ambient pressure (may I know the inlet/outlet absolute pressure?)
Check the mass continuity at inlet/outlet and you will "debug" your solution. The inlet mass flow rate (in kg/h) should be the same as the outlet mass.


Regards

[praroopjain]

Absolute Pressure at both the ends (inlet/outlet) is same as that of atmospheric pressure (i.e. 1 atm).

[MB72]

Originally Posted by praroopjain

Absolute Pressure at both the ends (inlet/outlet) is same as that of atmospheric pressure (i.e. 1 atm).

OK. I think we have a problem.
If we want to have a movement of the fluid (air) from inlet to outlet we need to establish a pressure difference between inlet and outlet, or the fluid doesn't move.
My suggestion is to use a much more robust strategy to solve the problem:
1)INLET: impose just mass flow rate (starting with a very low mass flow rate)
2)OUTLET: impose the pressure (in this case 1 atm)
3)Check carefully the results and determine the average inlet pressure.
4)Check if the outlet mass flow rate is the same (within 1% of the value) of those imposed at inlet.
5)Eventually you will use this pressure value in a final (much refined) simulation.

Regards

[praroopjain]

Ok, I m gonna try it.
Thanks