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Old   June 26, 2011, 18:00
Default Results of CFX Simulations
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AyAhSof
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Helo,
I've done simulations, usin' CFX, on rotor passages. In the results i have noticed negative pressure values. I know that negative velocity values means that the fluid particule is movin' in the opposite direction, but i dont understand the meanin' of negative presuure values. Also, in papers reserchers show countours containin' regions of negative pressure.
NB: I'm speakin' about countour pressure values, not values of pressure difference witch can mean that the flow is in opposite direction.
I'll be gratefull if somebody explaine to me this.
Thanks.
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Old   June 26, 2011, 18:35
Default turbomachinery velocity diagram in CFX
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Hello,
Usin' CFX Simulations on compressor passages, I have difficulties understandin' the absolute velocity and the relative velocity knowin' that in my results i have countours of Cm; W; velocity; ...
I know that C=W+u; when C absolute velocity W relative velocity u speed of rotor, but in CFX documentation, i have found somewhere (with figures) the decompostion of V to streamwise velocity; spanwise velocity; circumferential velocity or to axial velocity; radial velocity, circumferencial velocity and also to Blade to blade velocity ...etc.
So is V absolute or relative velocity; or can we say that C= (that V)+u; and how can we obtain in resutls Cu velocity; Cr velocity; Wu velocity; Wm velocity; Wr velocity.
Can somebody help me understandin' this, or tell me in what part exactly of CFX documentation can i found the details of that (maybe i didn't searche well in it).
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Old   June 26, 2011, 21:19
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Glenn Horrocks
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Pressure is measured relative to a reference pressure. A negative pressure simply means the pressure is less than the reference pressure. If the reference pressure is one atmosphere then a nagative pressure simply means a vacuum.
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Old   July 9, 2011, 06:15
Default meanin' of Negative pressure values
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Dear Ghorrocks,
Thank you so much for helpin' me understandin' negative pressure values.
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