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Spiegel May 9, 2001 06:02

Simulation of fluid flow through nozzles
 
Has someone got any idea/experience on this topic? Where can I find related information? Any CFD software, which is able to model a free jet of liquid (or even in air)? Tipical values: 200-1000bar, 20(!)-150micron orifice diameter.

John C. Chien May 9, 2001 12:33

Re: Simulation of fluid flow through nozzles
 
(1). If it is a free jet, then why not use the analytical solutions? You can find the solution in the "boundary layer theory" book by Schlichting. (2). In the book, there is a chapter on Free turbulent flows;Jets and wakes. (3). For round jets, it turns out that the analytical solution is the same because the viscosity and eddy viscosity are constant for laminar and turbulent flows, respectively. (4). So, the analytical solution of a free jet can be applied to any size jets.

Astrid May 9, 2001 16:32

Re: Simulation of fluid flow through nozzles
 
What is the purpose of your research? What do you want to spray? What are the inlet and outlet pressures?

Spiegel May 10, 2001 03:30

Re: Simulation of fluid flow through nozzles
 
Hello, Astrid! It's a sort of cutting application in a new kind of way, see: www.synova.ch. (I'm working on a PhD thesis in this field.) Thus, my aim is to get a non-cavitating "coherent" jet as long as possible. I mean the breakup length should be long even when using very small nozzles (down to 20microns in diam.) Typical water pressure is between 100-1000bar, the jet is exiting into the atmospheric air. The water-jet will not necessarily cut by itself, but a laser beam is injected in it. The jet acts like an optical waveguide plus a cooling agent, the laser cuts. So, it's like a focus-less, chilled laserbeam. But, as the jet gets disturbed the light scatters out of the beam and efficiency is lost. Cavitations result in lower cut quality. The final aim is a better nozzle design for this application. Synova has a lot of experimental knowledge on micro water-jets, but I want to put the whole stuff onto theoretical basis. Thanks, S


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