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Incompressible and compressible flow.

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Old   September 24, 2013, 08:53
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Filippo Maria Denaro
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Originally Posted by mercy.gh View Post
Hello,
In addition to the interesting conversation;
Measuring the Mach number also demands attention to the temperature of your environment, since the speed of sound would change correspondingly.
I am trying to simulate a combustion chamber with a high velocity fuel -oxygen injection.Really close to the injectors(before combustion happens) flow is definitely compressible (velocity of injection is 500 and sound almost 380) but in a small distance, when combustion happens Temperature will rise highly and the velocity of sound will increase to 800 which makes the Mach number much less!

Should I consider this compressible or in-compressible flow?
what about the velocity? if V/800 < 0.3 you can consider the flow incompressible in terms of acoustic wavew but you still have dependance of density due to high temperature gradients
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Old   September 24, 2013, 09:58
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Originally Posted by FMDenaro View Post
what about the velocity? if V/800 < 0.3 you can consider the flow incompressible in terms of acoustic wavew but you still have dependance of density due to high temperature gradients
True, I must consider this compressible. I just have never worked with that!
Thank you
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Old   January 30, 2014, 07:32
Default Deflagration not Detonation
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with respect to the earlier posts on combustion effects on what would normally be incompressible flow, simple temperature correction accounts for change in density. you could use combustion intensity figures to plot the heat release and continually account for this?
i don't see the need for use of compressible flow considerations unless you are considering detonation.
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