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wrong velocity & temp at initialization

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Old   October 15, 2007, 09:15
Default wrong velocity & temp at initialization
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I've got an Issue concerning total gauge pressure. I know this topic has been discussed numerous times, but so far I have not come across a thread, that would answer my particular question.

I work on simulating a free-flow at M=0.8, p_stat=26436.2426 Pa, and T=223.15K. I calculated the total pressure to be p_tot=40297.8223 Pa and the total temperature to be T_tot=251.7132.

I set the Operating Pressure to "0", input the p_tot for the Pressure Inlet at "Total Gauge Pressure", p_stat at Initial Gauge Pressure and T_tot at Total Temperature. So far so good.

When I want to initialize the calculation and set "compute from" to my Pressure Inlet, Fluent puts out a Gauge Pressure of 26436.18 Pa (not too far off), a velocity of 222.9477 m/s (at T=223.15 and 0.8M it should have been 239.704) and a temperature of 165.1291 (now, where did this come from). Via try and fail I found out that when I input a Total temperature of 323.2376 K and a Total Gauge Pressure of 38293.5 Pa I get the desired Initial Values. These Inputs don't mirror the real conditions though, so I wonder what I could be missing here.

Regards, Leo
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Old   October 15, 2007, 11:42
Default Re: wrong velocity & temp at initialization
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By the way - this problem occurs only, when in the material's setup cp is turned to kinetic energy.
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