The information above does not need to be used but is there

The information above does not need to be used but is there just in case.

Biomechanics 427 Problem Set 6 Data Humans mass 70 k total body height 2 m body diameter = 0.5 ml chest height 1.5 m pelvis height 1 m drag coefficient 05 Pterosaurs Each wing span= 5m Base of each wing 2m Lift coefficient of the wing 1.0 Drag coefficient of the wing = 0.1 Mass 250 kg Density of air 1 kg/m 3 Dynamic viscosity of air - 15 103 kg/m s Density of water 1000 kg/m3 Dynamic viscosity of water 103 kg/ m s Equations: Drag-pscaU2 high Reynolds number limit (S is the projected area) Drag-3d low Reynolds number limit Lift on a wing ps2 S is the planform area of a wing 1. Newton\'s law of viscosity suggests that a fluid moving tangential to a surface exerts a stress on that surface. Explain briefly why there can be a stress on the surface even though according to the \"no-slip\" condition there is no motion at the interface of the fluid and the surface itself. (1 pt)

Solution

The amount of friction depends upon the viscosity of fluids as well as the velocity gradient of the fluid. That is relative velocity between layers of fluids.

At No Slip Condition, the surface doesn\'t move, hence there is no movement (relative motion) for the liquid in contact with the wall. This region (layer) is very thin, namely Boundary Layer.

The most important consequence is that since the wall doesn\'t move, the velocity gradiant near the wall is so great in magnitude. Hence viscous stress are produced near the wall irrespective of the lack of relative motion at the boundary (despite No-Slip condition)