3.1. Definition of Boundary Layer Thickness

Try these first

1. 1.

   Define boundary layer thickness.

   Hint

   Think about how far from the surface the flow is still affected.

2. 2.

   What does laminar sublayer refer to?

   Hint

   Consider where viscosity plays a strong role near the surface.

3. 3.

   What defines the boundary layer thickness?

   • The distance to where velocity is 75% of free stream
   • The distance where velocity is 99% of free stream
   • The thickness of the entire laminar sublayer

   Hint

   Remember how we measure boundary layer effects.

4. 4.

   True or False: The laminar sublayer exists only in turbulent flow.

   • True
   • False

   Hint

   Consider the flow types.

5. 5.

   Given a fluid with a viscosity of 1 mPa.s and a density of 1000 kg/m³ flowing over a flat plate with a length of 5 m, what is the boundary layer thickness at the trailing edge if the free stream velocity is 2 m/s?

   Hint

   Apply the appropriate formulas for boundary layer thickness using the free stream conditions.

6. 6.

   Discuss the implications of increased boundary layer thickness on the drag force acting on an object moving through a fluid.

   Hint

   Consider how this might affect performance in engineering designs.