average velocity in pipe flow

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

hello sir, I am solving turbulent flow in a rectangular manifold. my question is in inlet boundary condition i want give velocity as input condition.  since my diameter is 1.7 cm I assigned a value of 0.5 m/sec in my z direction. Now i find a tab for average velocity when i opt my turbulence type for intensity and length scale. my question is how much should my value be in average velocity ??? Should my z-direction velocity be equal to the average velocity or something else. Can anyone explain me the concept behind this 

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Answers

  • cfdguru
    cfdguru New Altair Community Member
    edited August 2014

    AcuConsole requires various inputs in order to automatically compute the turbulence parameters.  One of those inputs is a velocity scale.  So, the velocity that you enter is the one that is used as the velocity scale.  For the case of a simple, constant velocity inlet, the velocity scale should be equal to the average velocity at the inlet.

     

    Here is a good reference:  http://www.cfd-online.com/Wiki/Turbulence_free-stream_boundary_conditions
     

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited August 2014

    thanks a lot for the right information. also, my doubt is regarding the BC at inflow. The velocity which we specify in x,y,z direction, is it called the total velocity i.e u = u avg +fluc.vel

    where U = sqrt(ux2+uy2+uz2). So i should specifu velocities in coordinate axis and average velocity U is derived from the above formula.

    My question is I should get U average as output. so in order to get that as output what should I follow. 

    Also should my turbulence scale and velocity scale be equal..

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