先进材料疑固实验室 Momentum transfer Laboratory of Advanced Materials Solidification Boundary layer,The layer where the flow speed higher than 0.99 times of the average flow speed.The thickness from the wall to where the flow speed is 0.99 times of average flow speed called as the boundary layer thickness. Re= ovl Re,<2x105 Re,>3x106 Laminar flow area: Turbulent flow area: Where the boundary Where the boundary layer thickness increase layer thickness increase slowly. sharply. 上游文通大学 SHANGHAI JIAO TONG UNIVERSITYMomentum transfer Boundary layer, The layer where the flow speed higher than 0.99 times of the average flow speed. The thickness from the wall to where the flow speed is 0.99 times of average flow speed called as the boundary layer thickness. µ ρvl Re = 5 Rex < 2×10 6 Rex > 3×10 Laminar flow area: Where the boundary layer thickness increase slowly. Turbulent flow area: Where the boundary layer thickness increase sharply