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-   -   Low Reynolds Number Flow over a Flat Plate (https://www.cfd-online.com/Forums/fluent/36467-low-reynolds-number-flow-over-flat-plate.html)

Go April 22, 2005 12:12

Low Reynolds Number Flow over a Flat Plate
 
All,

I'm trying to model simple flat plate flow (2D) and compare to Blasius' solution for model validation. I'm modeling a 0.5m plate with a 0.1m symmetry leading "edge" portion. I use a uniform velocity for the inlet and at the outlet I use a gauge pressure of 0. At the far field boundary I also use a gauge pressure of 0. I've stretched the mesh for boundary layer refinement and refinement near the leading edge of the plate (but no the flow domain). When I run with a Re=7e4 I get good results that compare well with Blasius. When I reduce Re by 1-2 orders of magnitude I no longer get accurate results. In fact I get "acceleration" in the bloundary layer where the velocity is greater than the free stream. I've tried increasing the height of my far field boundary to no avail. Any suggestions?

Mehdi Ghoddosy April 24, 2005 05:13

Re: Low Reynolds Number Flow over a Flat Plate
 
Dear Go: In Re=7e4 the flow is fully turbulent and inner sublayer and overlap layer thickness is going to vanish. But when you reduce the reynolds number you have to acount for inner sub layer and overlap layer. In this condition blasius sulotion does nnot prevail. Also you have to use wall function in your fluent turbulence model. regards

Basilisk February 25, 2010 19:15

I'm experiencing the exact same problem as the original poster, but I don't see what the reply was getting at. Yes downstream of the plate, turbulence will begin to generate and create sub layers and so on, but that does not explain flow acceleration, particularly if it is occurring not too far downstream from the plate edge, well before the growth of such layers. The question is, how can flow accelerate? Where is it gaining energy from? The plate can only take away from the kinetic energy via viscosity, not add to it.

vmlxb6 February 25, 2011 23:18

flow over a flat plate
 
Did anyone find the solution ???? I am facing the same problem. My inlet velocity is 0.00133 m/s but the vel contours show max velocity of 0.0015 m/s ???? Where does it get the additional energy from ??? also I am unable to verify using Blausius sol. ??? Has anyone solved the problem of a flow over a flat Plate ???

rameshbhoraniya August 28, 2013 05:19

Boundary Layer Flow
 
Dear All

I am also facing the same problem.

i have try to solve flow over plate as well as flow over a cylinder . both are same case , first is plane 2-D AND other is Axisymmetric . the result a am getting. above boundary layer i.e between boundary layer and free stream value of velocity increases then that of inlet uniform velocity . 1.00 to 1.0086 and the reduces to again 1.00 at free stream.

suggestions are appreciated, to get solution.


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