13.6.1. Concept and Mass Conservation

Try these first

1. 1.

   What is the significance of mass conservation in fluid flow?

   Hint

   Think about how water flows in a river.

2. 2.

   Define displacement thickness.

   Hint

   Consider how a car affects the air around it.

3. 3.

   What does mass conservation state in fluid dynamics?

   • Mass can be created
   • Mass can be destroyed
   • Mass must remain constant

   Hint

   Consider the principle of fluid flow in a pipe.

4. 4.

   True or False: The wall shear stress is influenced by the thickness of the boundary layer.

   • True
   • False

   Hint

   Think about how thicker layers might change fluid interaction with the surface.

5. 5.

   A flat plate in air flow shows a boundary layer of 1.5 mm at a velocity of 5 m/s. If the viscosity of air is 1.8 × 10^-5 Pa.s, calculate the shear stress at the wall.

   Hint

   Determine the gradient near the wall using velocities.

6. 6.

   If a wind tunnel with a diameter of 30 cm is designed for laminar flow at a speed of 4 m/s, what will be the Reynolds number? Will the flow remain laminar or transition to turbulence?

   Hint

   Calculate using viscosity and density at the given temperature.