3.4

Explain the properties and effects of boundary layers in a flow

field.

1. Consider the scenario where fluid is flowing over a surface. The

boundary layer develops from laminar to turbulent. Produce a

sketch that indicates the following key properties within the

boundary layer:

A. Laminar and turbulent boundary layer

B. Transition point

C. Velocity gradient

D. Boundary layer thickness

E. Free stream velocity

2. Explain why fluids which have higher viscosity have a larger

boundary layer thickness.

3. Flow can separate when an adverse pressure gradient occurs

over the wing of an aircraft. Explain what is meant by an adverse

pressure gradient and how this leads to flow separation. Briefly

explain the effects of flow separation on the wing.