16.4.2. Dynamically Similar Conditions and Force Calculation

Try these first

1. 1.

   What is shear stress in fluids?

   Hint

   Think about forces acting on a flat surface.

2. 2.

   What does viscosity measure?

   Hint

   Consider thicker liquids like honey.

3. 3.

   What is the formula for Reynolds number?

   • Re = ρVD/μ
   • Re = μVD/ρ
   • Re = ρ/μVD

   Hint

   Remember it’s a ratio involving forces.

4. 4.

   True or False: An increase in viscosity leads to a lower Reynolds number.

   • True
   • False

   Hint

   Think about what happens when a fluid becomes thicker.

5. 5.

   Calculate the forces acting on a model car in a wind tunnel if the drag coefficient is 0.3, frontal area is 2m², and air density is 1.225 kg/m³ at a velocity of 15 m/s.

   Hint

   Use the drag force formula to calculate.

6. 6.

   For water flowing over a sphere with a diameter of 0.2m at a velocity of 1m/s, calculate the Reynolds number given water's density is 1000 kg/m³ and viscosity is 0.001 Pa.s. Is the flow laminar or turbulent?

   Hint

   Remember the flow type depends on the value of the Reynolds number.