Exercise 14

1. Calculate the hydraulic radius of the circular pipe and trapezoidal concrete channel shown below. Assume the concrete channel is symmetric and the length units are meters.

2. If the flow is 0.005 m³/s, what is the mean velocity for each conveyance?
3. What is the Reynolds number for each conveyance? Assume water temperature is 20^o C.
   Hint: The kinematic viscosity [m²/s] is the ratio between the dynamic viscosity of a fluid [(1 Pascal-second) = 1 kilogram/(meter-second)] and the density of a fluid [kg/m³]. The SI unit of the kinematic viscosity is m²/s. Other units are:

• • 1 St (Stoke) = 1 cm²/s = 10⁻⁴ m²/s;
  • 1 cSt (centiStoke) = 1 mm²/s = 10⁻⁶m²/s; and
  • Water at 20 °C has a kinematic viscosity of about 1 cSt.

4. Is flow laminar or turbulent in each conveyance?
5. If the flow is 0.005 m³/s, what is the mean velocity for each conveyance?

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