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What is difference between static pressure and gauge pressure?

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Old   July 20, 2018, 11:32
Default What is difference between static pressure and gauge pressure?
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As you know, boundary condition of pressure in FLUENT set in form of gauge pressure.
The gauge pressure computes as follows:

Gauge pressure=absolute pressure- operating pressure or reference pressure or atmospheric pressure

Now, in my simulation and in pressure contours, pressure is static pressure. In addition, total pressure is related to static pressure as follows:

total pressure=static pressure+dynamic pressure

In this simulation, there is negative static pressure. Why does this happen? What does this mean? The negative Gauge pressure means that pressure is below atmospheric pressure, But in case of static pressure, what does mean?

I have some other question:

1. How can I relate static pressure (in contours) to gauge pressure (in boundary condition)?
2. Is static pressure equal to gauge pressure? or not? What is difference between them?

I am grateful that guide me in these cases.

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Old   July 20, 2018, 20:05
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There is static pressure and total pressure and you get the relation between them.

Then there is how you express static pressure and total pressure (in an absolute scale or a gauge scale). All pressures in Fluent are gauge pressures, there are no absolute pressures. The gauge is set by the operating pressure.

When you make a static pressure contour, you see are seeing a static gauge pressure contour. The Fluent interface does not spam repeatedly the words "gauge pressure" because it's written in the manual, all pressures are gauge pressures.

The same is also true for you. When you say static pressure, you need to be more disciplined and state how you express that pressure. Atmospheric pressure is with respect to what gauge? Are you using an absolute gauge? Or do you have your own gauge?
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