4 Replies Latest reply on Oct 10, 2017 8:59 AM by Siavash Khajehhasani

    What is the difference between "static, environnemental and total pressure"?

    Remal Youcef

      Hello;

      What is the difference between "static, environnemental and total pressure" and when we use each of them?

      Thanks.

        • Re: What is the difference between "static, environnemental and total pressure"?
          Matt Peneguy

          I think your terminology is a little different.  But here's a good explanation:

          Pressure measurement - Wikipedia

          • Re: What is the difference between "static, environnemental and total pressure"?
            Mark Keown

            Click on the help button and you will find joy and happiness.

            • Re: What is the difference between "static, environnemental and total pressure"?
              Siavash Khajehhasani

              Hello Remal,

               

              Static Pressure:

              In fluid dynamics, static pressure is the pressure at a nominated point in a fluid.

              In Aerodynamics: To distinguish it from the total and dynamic

              pressures, the actual pressure of the fluid, which is associated not with its motion but with its state,

              is often referred to as the static pressure, but where the term pressure alone is used it refers to this

              static pressure.

               

              Dynamic Pressure:

              In incompressible fluid dynamics dynamic pressure (indicated with q, or Q, and sometimes called

              velocity pressure) is the quantity defined by: q = ½ ρv²

               

              Total Pressure:

              In fluid dynamics, total pressure (p0) refers to the sum of static pressure p, dynamic pressure q,

              and gravitational head, as expressed by Bernoulli's principle:

              p0 p = q + ρgz

              The total pressure is also called stagnation pressure.

              The basic impact tube consists of a tube pointing directly into the fluid flow. As this tube contains

              fluid, a pressure can be measured; the moving fluid is brought to rest (stagnates) as there is no

              outlet to allow flow to continue. This pressure is the stagnation pressure of the fluid, also known as

              the total pressure or (particularly in aviation) the Pitot pressure.

               

              Environment Pressure:

              Unlike static, dynamic and total pressures, the Environment Pressure is not a physical quantity. It is

              merely a type of boundary condition in Flow Simulation. The Environment Pressure condition is

              interpreted by Flow Simulation as a total pressure for inlet flows and as a static pressure for outlet

              flows. If in the course of calculation a vortex crosses an opening with the Environment pressure

              condition specified, this pressure is considered as the total pressure for the part of opening through

              which the flow enters the model and as the static pressure for the part of opening through which the

              flow leaves the model.

               

              Now the question could be: what if you apply static pressure at outlet of equal magnitude instead of environmental pressure, how different your results are going to be?

              The only difference between static pressure and environmental pressure depends if there is vortex

              flow near the opening. If there is no vortex flow then there should be no difference.

              If there is a vortex near the opening, the flow that is coming back through the opening is calculated

              using static pressure if a static pressure boundary condition is applied at the opening. If

              environmental pressure is used as the boundary condition then the flow is calculated assuming total

              pressure. Environmental pressure is more accurate if there is vortex flow near the opening. If there

              is no vortex flow near the opening then the results should be the same no matter if you use static

              pressure or environmental pressure.

               

              Regards,

              Siavash