17.6.3. Impact of Reynolds Number and Surface Roughness

Try these first

1. 1.

   What is the formula for calculating Reynolds number?

   Hint

   Identify the terms involved in the equation.

2. 2.

   What does a high Reynolds number indicate about flow?

   Hint

   Think about flow characteristics.

3. 3.

   What does a Reynolds number greater than 4000 indicate?

   • Laminar Flow
   • Transitional Flow
   • Turbulent Flow

   Hint

   Relate the number to flow regime definitions.

4. 4.

   True or False: A higher surface roughness always increases drag.

   • True
   • False

   Hint

   Think of examples in design contexts.

5. 5.

   Evaluate the drag force on an object with Cd = 0.7, A = 2 m², ρ = 1.225 kg/m³, and v = 30 m/s.

   Hint

   Use the drag force formula correctly.

6. 6.

   A smooth sphere has a Reynolds number of 2500. Discuss flow characteristics and if you expect high or low drag.

   Hint

   Relate Re values back to flow characteristics.