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Old   July 11, 2008, 05:19
Default problem with boundary layer
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hello everyone,

I have a problem regarding the simulation. my geometry consists of a ramp along with the sidewall which is at one end of the ramp .sidewall being triangular and is just a plate. I am using a research code for simulation. the problem is I am getting a good boundary layer dveloped on the ramp but could not get on the sidewall. on the sidewall i am able to get BL only in the 1st cell. the grid size is fine enough y+ is 1 to capture the boundary layer and i am running viscous simulation. does anyone have an idea why BL is not developing on the sidewall.
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Old   July 11, 2008, 09:06
Default Re: problem with boundary layer
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I have a little difficult to understand exactly the symmetry of your flow and the domain of the simulation. What is the direction of the flow...If this is a 3D, then you have more than just a wall and a "ramp", and what is meant by a ramp? Did you check that the viscous terms enter the equations in all the dimension? Not sure also where the "triangular" enters the picture. If you have a link to the exact problem or a image, or something. The BL will develop when the fluid flows parallel to a surface onto which the velocity is set to zero. Make sure you don't have on one of the surface a non-slip condition. If the viscosity of the flow is nu, then the bouundary layer will develop on a size D, where

D =nu/v

and v is the velocity of the flow (In the boundary layer one has a Reynolds number of order 1). So make sure you have the size D over at least a few cells/grid poins.

Rey = (D*v)/nu = 1 in the BL (this is a first approximation). If you increase the viscosity you will increase the size of the BL, so that's also a good way to check what's happening.
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