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Eddies in Laminar ?

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Old   December 14, 2002, 14:45
Default Eddies in Laminar ?
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bharath
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Hello

I would like to knw if an eddy or..any vortices,,,can be created in laminar flows in ducts,channels etc ?? if such interactions are present..is it wise to assume Steady State assumptions for CFD problems...??

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Bharath
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Old   December 16, 2002, 03:56
Default Re: Eddies in Laminar ?
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Dean
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Laminar flows can contain vortices, and they can be unsteady. It depends on the details of the problem you are interested in.
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Old   December 16, 2002, 13:51
Default Re: Eddies in Laminar ?
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bharath
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hello consider a case of BAckward Facing Step...in a rectangular duct due to sudden increase in the diameter of the duct ..is it possible that the vortex generated ...is due to a Laminar flow ?

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Bharath

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Old   December 16, 2002, 19:19
Default Re: Eddies in Laminar ?
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Dean
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Maybe - check the Reynolds number.
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Old   December 17, 2002, 00:05
Default Re: Eddies in Laminar ?
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greg
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Vortices are not generated "because" the flow is laminar, but vortices can exist in laminar flows - the classic case is cross-flow over cylinder. At very low Re, the flow is attached. As the Re number increases the flow detaches, forming standing eddies as the shear layers roll up. Beyond a certain value of Re (O(100) as I recall, but it's been a while) the eddies begin to shed. The flow is still laminar, the vortices are created by the vorticity contained in the separating shear layers, and the flow is strongly unsteady.
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