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ufechner May 14, 2009 04:53

Static Pressure, Total Pressure
 
Hello,

I have an air heating with an inlet and an outlet.

For the outlet I want to define the pressure.

Can anyone explain to me the difference between:

- environmental pressure
- static pressure and
- total pressure

Which type should I use?
(I am definitly in the undersonic range).

Regards:

Uwe Fechner

qihongming May 26, 2009 09:00

There are two ways to measure pressure in fluid flow: Static Pressure, P, and Total (Stagnation) Pressure, Pt.
Static pressure is the pressure indicated by a measuring device moving with the flow or by a device that introduces no velocity change to the flow.
The usual method for measuring static pressure in a flow along a wall is to drill a small hole normal to the surface of the wall and connect the opening to a manometer or pressure gage. In the region of the flow away from the wall, static pressure can be measured by introducing a probe, which in effect creates a wall.
Total pressure is the pressure measured by bringing the flow to rest isentropically (without loss).
A device for measuring total pressure is the Pitot tube, an open-ended tube facing directly into the flow.
Dynamic pressure = * Density*Velocity^2
Dynamic pressure can also be defined as the difference between the Total pressure and Static pressure.
Ptotal = Pstatic + Pdynamic


matheusguzella July 24, 2009 08:34

Pitot Tube
 
Quote:

Originally Posted by qihongming (Post 217205)

A device for measuring total pressure is the Pitot tube, an open-ended tube facing directly into the flow.
Dynamic pressure = * Density*Velocity^2
Dynamic pressure can also be defined as the difference between the Total pressure and Static pressure.
Ptotal = Pstatic + Pdynamic


Hi,

You sure that the Pitot tube measure the total pressure? Don't you mean dynamic pressure? Sorry if it's a dumb question!

murat August 5, 2009 14:28

Ihttp://www.efunda.com/designstandard...tot_tube_B.gif


If you see the picture, you can see where the total and static pressure is measured. Stagnation point means total pressure point( Pressure is max and velocity "0"" Total pressure includes Dynamic pressure and static pressure also. If you create a boundary condition for outlet always you can use static pressure. Environment pressure in FloEFD has two meanings. If you want to create inlet pressure by Environment pressure in Floefd it means total pressure. If you want to create outlet pressure by Environment pressure in FloEFD it means static pressure.


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