How to determine Re of a pipe flow (Poiseuille) when pressure inlet and outlet is set

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 March 3, 2019, 23:29 How to determine Re of a pipe flow (Poiseuille) when pressure inlet and outlet is set #1 New Member   Js Join Date: Dec 2012 Posts: 6 Rep Power: 12 In a 2D pipe flow (Poiseuille flow) Re = U*2R/nu, where R is the radius of the pipe. If I set inlet as U, then I can control the Re by varying viscosity nu. However, if in the simulation, the pressure inlet and outlet is prescribed, how do I control Re? For example, if I set Re = 100, how should I set nu? nu is supposed to nu = U*2R/Re, however, U is not known a prior as pressure is given in the inlet and outlet. Thanks

March 4, 2019, 03:06
#2
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Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,290
Rep Power: 67
Quote:
 Originally Posted by wertyfg In a 2D pipe flow (Poiseuille flow) Re = U*2R/nu, where R is the radius of the pipe. If I set inlet as U, then I can control the Re by varying viscosity nu. However, if in the simulation, the pressure inlet and outlet is prescribed, how do I control Re? For example, if I set Re = 100, how should I set nu? nu is supposed to nu = U*2R/Re, however, U is not known a prior as pressure is given in the inlet and outlet. Thanks

This is a homework you can find in any textbook. Just as hint, write the momentum along the streamwise direction. You will see a relation between the pressure gradient and diffusive term along r.

 Tags poiseuille flow, pressure boundary, reynolds number