Hello,

We r doing single phase simulations for stirred vessels. Our intention is to get pressure profiles around the impller blades. We came across various terms such as static,dynamic and absolute pressure etc. However, the static pressure over a horizontal line is varying with radial position. After going through definitions of all the above mentioned terms it is not clear to us how these variable r defined in fluent. Could any body shed some light on this ??

Regards, Murthy&Niteen

You must have realised this from the definition.

P(total)=P(static)+P(dynamic) --- for incompressible flow, from bernouli equn

Thing to keep in mind that, Fluent takes input or gives output in terms of gauge pressure for any of these presssures. That is, P(gauge)=P(operating)-P(absolute)

P(operating) is the pressure that you define in the operating condition panel.

Regards -US

Many thanks for ur comment and I totally agree with you. But my concern is How come static pressure can be +Ve,-Ve over a horizontal plane or line. This is some thing i am not getting. Hoping again ur comments . Regards Murthy

Hi Murthy,

Can't tell about your results. But with my understanding, static pressure can be different even at same elevation. For example, if we consider flow through horizontal ventury, then static pressure at the throat of the ventury is less than the static pressure,measured at the same elevation, at the inlet. However, your case is stirred tank with single phase. It should be interesting to know what causes this to happen or if it is correct. I'm not familiar with rotating flow that usually has strong body forces. Such flows should be causing large pressure fluctuations in the domain. Also, in your case, lift and drag forces may aslo come into picture due to the stirrer geometry. Means, there is going to be some difference in static pressure on horizontal line if that is near to the stirer body. The +/- values may be bcs it is gauge pressure with respect to operating pressure.

when you find out,please mention your analysis here or email to me so that it helps to improve my understanding and also of others who needs to.Thanks in advance for that. Regards, -US

Many thanks for ur kind interest. You are right, i have checked using custom fields, it is understood that static pressure is equal to gauge pressure.Now Interesting part is how can we differentiate dynamic n static pressure. You rightly pointed out other body forces i will think on that line. Sure,I can always send you my predictions. Regards, Murthy

Hi, I would like to check what is the maximum pressure difference that a diamnond window of 1 or 2 micron thickness can stand when having on the one side vacuum and on the other side gases between 0.2-5 atm. Thanks in advance