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getting negative static pressure on airfoil surface

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Old   July 15, 2014, 12:57
Default getting negative static pressure on airfoil surface
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rishad rizwan
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hello all!
i am doing a simulation in ansys fluent on flow over an airfoil at transonic speed. i got very good Cl , Cd and Cp distribution. but i'm getting negative static pressure when i'm monitoring surface points on the foil. also my static pressure contour shows negative area...

i've set the operating pressure = 101325 Pa
in B.C, gauge pressure = 0 Pa

i cannot detect the fault....as i went through some tutorials and followed them..... would you please say me how to encounter this problem of negative static pressure ?

thanks and regards.
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Old   July 15, 2014, 13:37
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it simply shows that velocity is increasing
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Old   July 15, 2014, 13:45
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rishad rizwan
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hello far
how can pressure be negative on airfoil surface ? shouldn't it be of some positive value ?
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Old   July 15, 2014, 14:16
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Quote:
Originally Posted by rishad View Post
hello far
how can pressure be negative on airfoil surface ? shouldn't it be of some positive value ?
You are correct.

Absolute pressure = atmospheric pressure + gauge pressure

Results you are getting are in terms of gauge pressure, just add atmospheric pressure to get some positive value
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Old   July 15, 2014, 14:27
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thank you sir... but can you clarify me one more thing please ? in ansys tutorial : fluent_13.0_workshop02-airfoil.pdf , they set
# the operating pressure = 0 Pa
# Pressure (gauge) at Boundary condition, P = 71150.4 which they obtained from Po/P relation.

and in my simulation i set # operating pressure = 101325 Pa
and boundary condition # gauge P = 0 Pa
when i tried that of ansys tutorial i got positive pressure but my set up produces negative one... would u explain this please ? i need to know which one is correct ?

thank you for your time.
regards
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airfoil analysis, flow over airfoil, negative static pressure, pressure contour

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