# turbulent jet into the atmosphere

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 June 20, 2001, 09:11 turbulent jet into the atmosphere #1 Henry Pastohr Guest   Posts: n/a Hi all, Can anybody help me with a problem of a turbulent jet into the atmosphere with a Re number of 10^6. I will simulate this with a commercial cfd code (fluent)and don´t know the area witch is needed that the jet is far away from the boundaries.I have one inlet boundary. The other boundaries are solid borders. Can I do 10 times the biggest geometrical dimension or 100 times. I run an transient simulation.

 June 20, 2001, 10:55 Re: turbulent jet into the atmosphere #2 Kike Guest   Posts: n/a Dear Henry I don't understand very well why are you talking about a "jet into the atmosphere" and the boundaries are solids!!!. Can't you use free/open boundary conditions for your case in FLUENT. What exactly do you want to study? Watch out your distances. 10 or 100 times (assuming the jet's diameter) depends on what you want to study. Regards Kike

 June 20, 2001, 11:46 Re: turbulent jet into the atmosphere #3 Henry Pastohr Guest   Posts: n/a Hallo Kike, Thanks for your quick answer. I simulate a temperature driving machine in the atmosphrere. The outlet of this machine produced this turbulent high Re number jet. When i use pressure boundary conditions for the boundaries the machine is then pressure driving and not temperature driving.That is not the same!! You get inflows and outflows on the boundary. But this is not the problem, then the safe distance to the boundary (wall or Pressure boundary) is unknown.The distance changes it between the simulation, because the simulation is unsteady. Is my solution to near the boundary, then i can forget my solution, because it is not boundary independent. Henry

 June 21, 2001, 08:44 Re: turbulent jet into the atmosphere #5 Henry Pastohr Guest   Posts: n/a Dear Kike, Thanks for your answer. The correct boundary far away from my machine is a problem , I know. I will order the literature witch you have advised, thanks.I will write you back,when i have read this. Do you know references for a "buoyant momentum jet" or forced plume in axissymmetric?? Good bye, Henry

 June 21, 2001, 09:55 Re: turbulent jet into the atmosphere #6 Xu Zhou Guest   Posts: n/a Hi there, They may interest you: (1) W. K. George and R. L. Alpert and F. Tamanini, "Turbulence measurements in an axisymmetric buoyant plume", Int. J. Heat Mass Transfer", 1977, vol. 20, 1145--1154. (2) A. Shabbir and W. K. George, "Experiments on a round turbulent buoyant plume", J. Fluid Mech. 1994 vol. 275, 1--32 (3) X. Zhou, K. H. Luo, and J. J. R. Williams, "Large-eddy Simulation of a Turbulent Forced Plume", European J. Mechanics, B/Fluids, Vol. 20, No.2, pp. 233-254, 2001

 June 22, 2001, 05:21 Re: turbulent jet into the atmosphere #7 Kike Guest   Posts: n/a Hi, Henry No, I am sorry. I will check those Mr. Xu Zhou had gave you. Bye Kike

 June 25, 2001, 08:12 Re: turbulent jet into the atmosphere #8 A. Hassaneen Guest   Posts: n/a hello, Could you please give us an idea of the geometry and the fluid of the jet?

 June 25, 2001, 08:18 Re: turbulent jet into the atmosphere #9 A. Hassaneen Guest   Posts: n/a hello, Could you please give us an idea of the problem geometry and the fluid and the of the jet?

 June 25, 2001, 09:10 Re: turbulent jet into the atmosphere #10 Henry Pastohr Guest   Posts: n/a Hallo Mr. A. Hassaneen, The outflow of the machine has a diameter of 10 meters. The geometrie of the outflow is a simple tube. A full turbulent velocity profile is assumed.The temperature profile is konstant. The outflow shows against the direction of the gravity.The fluid is air. At steady stage: The mean velosity is 5 m/s. The outflow temperature is 320 K. The atmosphere is at 300 K and in silence. Thanks for your Response Henry

 June 26, 2001, 03:57 Re: turbulent jet into the atmosphere #11 A. Hassaneen Guest   Posts: n/a Henry, I don't think that your problem needs any special treatment. It's an air jet discharging into air, you may need to specify a confinement to the jet and use an outlet boundary at certain distance from the jet (let's say 10 diameter) and see what happen. Be careful when you specify the turbulence model. I think your problem will be mainly with the continuity.

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