Boundary Layer Features Boundary Layers:Physical Features Velocity Boundary Layer Free stream 8(x Consequence of viscous effects Velocity boundary -A region characterized by shear layer stresses and velocity gradients. -between the surface and the free u(y=-0.99 stream whose thickness 6 increases in the flow direction.(m) Ou -Manifested by a surface shear stress =0 Us that provides a drag force,Fp. FD=∫t,dA N/m2) N)Boundary Layer Features Boundary Layers: Physical Features • Velocity Boundary Layer – Consequence of viscous effects – A region characterized by shear stresses and velocity gradients. ( ) 0.99 u y u δ ∞ → = – Manifested by a surface shear stress τs that provides a drag force, FD . FD s y 0 u y τ μ = ∂ = ∂ s D ss A F = ∫ τ dA – between the surface and the free stream whose thickness δ increases in the flow direction. (m) (N/m2) (N)