calculating stagnation pressure

uni_student · January 28, 2011, 09:02

Hello,

I am conducting a CFD analysis as part of a university project and have a question regarding the calculation and comparison of the stagnation pressure.

The flow is a supersonic compressible flow over a nose cone and I was told a quick check can be done to ensure a correct cfd model. This was to calculate the stagnation pressure using the formula below and comparing it to the static pressure from the analysis:

Stagnation Pressure = Static pressure(1 + 0.2*MachNo^2)^3.5 (assuming ideal gas)

However, my CFD model gives a static pressure of 299 kPa compared to a stagnation pressure of 371 kPa from hand calculations. This may sound really stupid but am I comparing the right values as I assumed the static pressure and stagnation pressure are different?

Any help will be greatly appreciated.

RossFS · January 28, 2011, 21:03

Static and Stagnation Pressures are different as you assumed.

To compare the stagnation pressures between what the code is producing and the hand calculation you have, can't you just substitute the static pressure from the software into the stagnation pressure formula you have and compare?

January 28, 2011, 09:02	calculating stagnation pressure	#1
uni_student New Member Join Date: Jan 2011 Posts: 1 Rep Power: 0	Hello, I am conducting a CFD analysis as part of a university project and have a question regarding the calculation and comparison of the stagnation pressure. The flow is a supersonic compressible flow over a nose cone and I was told a quick check can be done to ensure a correct cfd model. This was to calculate the stagnation pressure using the formula below and comparing it to the static pressure from the analysis: Stagnation Pressure = Static pressure(1 + 0.2*MachNo^2)^3.5 (assuming ideal gas) However, my CFD model gives a static pressure of 299 kPa compared to a stagnation pressure of 371 kPa from hand calculations. This may sound really stupid but am I comparing the right values as I assumed the static pressure and stagnation pressure are different? Any help will be greatly appreciated.

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January 28, 2011, 21:03		#2
RossFS Member Join Date: Feb 2010 Location: Australia Posts: 65 Rep Power: 16	Static and Stagnation Pressures are different as you assumed. To compare the stagnation pressures between what the code is producing and the hand calculation you have, can't you just substitute the static pressure from the software into the stagnation pressure formula you have and compare?