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jet oscillation at low inlet Re

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Old   October 21, 1999, 01:00
Default jet oscillation at low inlet Re
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Hi There is a question. When a plane jet issued from a nozzle hits a bluff body downstream in a confined chamber, there are two big vortexes in front of the bluff body and two small ones behind it. A disturbance will cause the plane jet oscillate. When the velocity at the nozzle exit is high, which is proportional to the inlet Re number, the whole flow field in the chamber is turbulent. When the inlet Re is low enough, the whole flow field is laminar and no oscillation exists. Now, I am interested in when the oscillation begins. Now I am using a software based on FVM to simulate the oscillation at low inlet Re. I wonder: 1. if part of the flow field is turbulent and the rest is laminar, what kind of model should I use? Since a model such as turbulent and laminar is defined as a whole, can I still use them? 2. is FVM suitable?

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Old   October 21, 1999, 13:45
Default Re: jet oscillation at low inlet Re
Jonas Larsson
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What you are trying to do is very difficult - predicting natural transition in an unsteady 3D flow.

Since this inherently is an unsteady 3D problem I would use LES. FVM is suitable for LES, but there are many things to think about in order to get good results. Your case is difficult enough to be a long-term research project.

Perhaps you could use some kind of simplified stability analysis to investigate when the flow will amplify a disturbance. Haven't got a clue how to best do it though. Anyone?

I'm probably saying obvious things here, I'd better stop my rants. Good luck!

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