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July 13, 2018, 11:55 |
Converging-diverging nozzle
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#1 |
New Member
Join Date: Jul 2018
Posts: 6
Rep Power: 7 |
So I'm new to Fluent and I'm trying to do a simulation of a Converging-diverging nozzle. For starts, I'm considering inviscid flow. I'm supposed to obtain a supersonic flow downstream the throat followed by a normal shock. However, I can't seem to achive these two phenomena. I think I'm messing something up setting the BC.
Here's what's given: * Mach number inlet: Ma= 0.239543 * Stactic pressure inlet: p_s_inlet=1 bar=10^5 Pa * Stactic pressure outlet: p_s_exit =0.83049*p_s_inlet * Total temperature inlet: 300 K I calculated the total inlet pressure using the Mach number and pressure relation. Set the Operating Pressure to 0, so I can work with absolute pressures. Here's what my inlet and outlet BC look like: Pressure Inlet: https://imgur.com/a/KzFpodi Pressure Outlet: https://imgur.com/a/F9JPnLE I'm working with air as an ideal gas. I set the inlet BC to Pressure Inlet because of compressibility. So, any ideas why I can't get to the results I need? Do you guys see anything wrong with the BC? I fully appreciate and look forward to your replies. Thanks in advance. Note: if imgur hosting is not appropriate I can change it. Sorry for anything. UPDATE: here are the contours of Mach numbers for the simulation with the BC above. It's converged in 2015 iterations. https://imgur.com/a/6kQxMOf |
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July 13, 2018, 18:12 |
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#2 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,666
Rep Power: 65 |
Is the throat area small enough to choke the flow?
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July 14, 2018, 05:08 |
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#3 |
Senior Member
Behrooz Jamshidi
Join Date: Apr 2013
Posts: 110
Rep Power: 13 |
This is not a CFD problem. First of all your flow needs to be choked. Choked flow is independent of geometry. For air as working fluid, your discharge pressure must be less than 0.53*Pinlet. While you set discharge pressure as 0.83* Pinlet, it is obvious that you can not get choked flow and subsequently shock.
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