# Help to understand these two images

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 March 12, 2006, 13:42 Re: Help to understand these two images #2 Mani Guest   Posts: n/a the term 'total pressure' is ambiguous, here, to say the least. it cannot be the absolute total pressure, because that cannot be zero. so it must be some kind of normalized or relative total pressure. i would assume that pressure zero really means "undisturbed freestream pressure", consistent with incompressible nomenclature (they should really learn that the world is compressible and name things in an unambiguous way). if that's true, then total pressure zero simply means zero velocity. zero velocity contours can help you identify regions of recirculation (separated flow) which are associated with drag, especially if the flow in those regions is very turbulent (much energy is dissipated). you will want to minimize those separations.

 March 12, 2006, 15:00 Re: Help to understand these two images #3 Freeman Guest   Posts: n/a Many thanks for your reply, Mani! I think that this total pressure is perhaps the static+dynamic pressure (without the atmosferic), so a ptot=0 is the zone where fluid has a zero velocity as you said. But I don't know what is the benefit of plotting the ptot=0 colouring it by the turbulent kinethic energy (TKE): is there any influence of the TKE on a fluid with zero velocity (ptot=0)? Thanks a lot!

 March 14, 2006, 09:11 Re: Help to understand these two images #4 Lars Ola Liavåg Guest   Posts: n/a Viscous losses makes ptot fall along a streamline. If the Opel people have used ptot=0 as the reference value at the inlet, ptot < 0 means you've had losses.

 March 15, 2006, 10:21 Re: Help to understand these two images #5 Freeman Guest   Posts: n/a Thanks Lars, very clear your last post! But is there any reason to colour this contour plot by the turbulent kinethic energy?I mean, the TKE has influence in the pressure to make these losses or it has nothing to do? Thanks a lot!

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