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Old   May 6, 2013, 13:15
Question Question about using total energy equation or thermal equation
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HI,

The tutorial tell that, for low-speed flow, thermal equation could be used instead of total energy equation to accelerate the computation. But how to know whether my case is 'low-speed' or not?

By the way, I'm simulating water. How to know whether the viscous term has to be included or not?
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Old   May 6, 2013, 14:19
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Only use the total energy equation related to high speed flow if compressibility is important. I think (I invite anyone to correct me here) it's a speed around mach 0.3 and above.

If you're using water, and your flow is subsonic you won't have heat generation due to viscous work, so I wouldn't worry about it.
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Old   May 6, 2013, 16:40
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Quote:
Originally Posted by RicochetJ View Post
Only use the total energy equation related to high speed flow if compressibility is important. I think (I invite anyone to correct me here) it's a speed around mach 0.3 and above.

If you're using water, and your flow is subsonic you won't have heat generation due to viscous work, so I wouldn't worry about it.

My flow speed is not that high. Is there is a way (or criteria) to detect whether viscous term need to be included or not?
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Old   May 6, 2013, 18:58
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The easiest way is to run a model with and without it and you will then see if it makes a difference.
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