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Old   November 20, 1999, 08:05
Default regarding low pressure handling
subodh kumar
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Dear Sir,

I am working on a flow and performance prediction through a 3D rectangular diffuser mounted on the downstream of Low Pressure Turbine using Fluent software. There are complexities in side the diffuser in the form of extraction pipes, low pressure heater ( cylinderical body ) and their supports. I am using two boundary conditions

a. velocity profile at the inlet

b. uniform pressure at the outlet, value being -90000 Pa (gauge) ie 10000 Pa absolute pressure.

After solving it, the pressure profile at the inlet is containing regions having pressure less than absolute zero. Pressure goes as low as -200000 Pa in some region which is physically impossible.

Can you suggest me some ways to overcome this problem. I have requested Fluent also for this, but could not get any suggestion. Please help me.

Thanking you,

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Old   November 20, 1999, 22:23
Default Re: regarding low pressure handling
John Chien
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(1). It is good, because the pressure is negative. Otherwise, it would be difficult to know whether the result is good or bad. (2). You have not defined your problem yet. It is important to know the computational domain, the Mach number, the Reynolds number, the turbulence model, the numerical method, the mesh, etc... (3). I would strongly suggest that, you check out the code in 2-D first on 2-D channel flow first, then 2-D diffuser flow next. If it still does not work, I think, it is time to find other alternatives. For example, writing your code, or have an expert to solve the problem for you. (4). There are many things which could go wrong in 3-D.
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