It is desired to determine the general features of boundary layers in fluids that obey Eq. (6.5-17). The velocity scale is U and the object dimension is L.

(a) Show that if δ⁄L ≪ 1, the momentum equation for a two-dimensional boundary layer is

Explain why the other viscous terms are negligible.

(b) What dimensionless parameter (a generalization of the Reynolds number) must be large if δ⁄L is to be small? Use OM estimates to deduce the dependence of both δ⁄L and τ₀ on n and on the generalized Re.

Transcribed Image Text:

дих UX ax +Uy дих ду du dx = U- + m д au. - р ду ду n (P9.10-1)