# Asymmetric water free jet study

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 June 20, 2001, 04:03 Asymmetric water free jet study #1 Norberto Parreira Guest   Posts: n/a Dear Sirs, I want to study an asymmetric water free jet discharging into the air (like the one found in Cross-Flow hydraulic turbine), using CFD codes. In my case, the free jet geometry must came out as a result, since it is unknown at the beginning. There are methods for potential flow analysis, but I never found anything for viscous flow. I don't know if there are any CFD software packages that can handle this kind of problem. I emphasize that we don't know the free jet surface shape. It can be shown that the pressure is constant on the jet surface (and, therefore, the velocity is also constant). Although we know the nozzle geometry, the flow calculation inside this region must take into account the shape of the free jet, which is not known at the start. I thank in advance for any help given.

 June 20, 2001, 11:09 Re: Asymmetric water free jet study #2 Kike Guest   Posts: n/a Dear Norberto I doubt that the pressure on the interface remains contant when a jet enter into the surrounding atmosphere, even if the air is "at rest". If the flow is viscous then you will have shear stresses and therefore, a spatial development of Kelvin-Helmholtz instabilities (maybe Rayleigh and Taylor intabilities), which are closely related to a pressure distribution on the inteface. If you know the geometry of your nozzle just send the water into the computation domain by this arbitrary shape orifice. Track the interface and you will find the shape. That is what we do. We (our group) works on liquid jets with and without air coflows, but I can't understand your last sentence. "the flow calculation inside this region must take into account the shape of the free jet, which is not known at the start". Please, be more clear if you can, and maybe we can help you a little. Regards Kike

 June 21, 2001, 17:37 Re: Asymmetric water free jet study #4 John C. Chien Guest   Posts: n/a (1). Most applications using Navier-Stokes code require the specification of the boundary conditions and the corresponding locations. (2). In your case, a model must be developed first to take the constant pressure as the boundary condition and the boundary location must be the part of the solution. (3). So, a method has to be developed first to do that. I don't know whether current commercial code can handle it or not. A code which can handle free surface might be a good place to start.

 June 21, 2001, 20:52 Re: Asymmetric water free jet study #5 Jim Park Guest   Posts: n/a The commercial code FLOW-3D was originally developed for this kind of application. The company, Flow Science, is a sponser of this web site. It's antecedents, SOLA-VOF, NASA-VOF/2D and NASA-VOF/3D also have a free service capability. I have no relationship to this company.

 June 25, 2001, 08:23 Re: Asymmetric water free jet study #8 A. Hassaneen Guest   Posts: n/a I have used (FIDAP) code to handle a Free Surface problem like this when I was simulating the fluid flow and heat transfer characteristics of a free liquid jet impinging on a hot plate.

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