The Convection Boundary Layers Velocity Boundary Layer Free stream 一6(x) Velocity boundary layer For fluid flow over a flat plate,which disturbs the fluid flow: -ASy→0： u=uo where u is velocity in x-direction Asy-→0： u=0 (no-slip condition) The boundary layer thickness is defined as the value at which: u(y)=0.99u。 - The boundary layer thickness 8 varies with x Shear Stress Bu ay Dynamic viscosity y=0 Local friction coefficient u 2 Heat Transfer Su Yongkang School of Mechanical Engineering# 11 Heat Transfer Su Yongkang School of Mechanical Engineering The Convection Boundary Layers Velocity Boundary Layer • For fluid flow over a flat plate, which disturbs the fluid flow: – As y→∞: where u is velocity in x-direction – As y→0: (no-slip condition) – The boundary layer thickness is defined as the value at which: – The boundary layer thickness δ varies with x • Shear Stress • Local friction coefficient =0 ∂ ∂ = y s y u τ µ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = ∞ 2 2 u C s f ρ τ = ∞ u u u = 0 = ∞ u( y) 0.99u Dynamic viscosity