Question

What is the limitation of the Shield’s expression?

(a) It can be used when the diameter of a particle (d) is < 6mm and Reynold’s number > 400

(b) It can be used only when Reynold’s number > 400

(c) It can be used only when the diameter of the particle is < 6 mm

(d) It can be used when the diameter of a particle is > 6mm and Reynold’s number > 400

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This interesting question is from Irrigation Channels Design topic in division Sediment Transport and Irrigation Channels Design of Irrigation Engineering

Answer 1

Right answer is (d) It can be used when the diameter of a particle is > 6mm and Reynold’s number > 400

Best explanation: The curve plotted by Shield between Reynold’s number and Entrainment function forms a suitable basis for the design of channels where it is required to prevent bed movement. When the particle size exceeds 6 mm such as for coarse alluvium soils, the particle Reynold’s number has found to be more than 400 representing roughness.