Unformatted text preview: s lots of eddies in it. Often a flow begins as laminar and at some point “transitions” to turbulent flow. Higher Reynolds numbers lead to turbulent flow. Transition is very difficult to predict, and predicting the transition point is one of the most difficult things for CFD codes to do. Transition to turbulence is driven by viscous effects, so unless something makes the incoming flow turbulent to begin with (not likely in our problems) we will only see turbulence in boundary layers and wakes. A preliminary look at boundary layers The thickness of the BL is exaggerated. The thickness is designated by δ, we call the velocity outside the boundary layer Vb Where the flow first encounters the body the boundary layer starts essentially δ = 0. Re can define x as the length along the surface. We can also define a Reynolds number As x gets bigger δ gets bigger too. At some point when Rex gets big enough the boundary layer will change from a laminar boundary l...
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- Fall '10