Question

(i) Explain the physical meaning of Reynolds number and Froude number.

A weir is an obstruction in a channel flow which can be calibrated to measure the flow rate. The flow discharge Q varies with gravity acceleration g, weir width b into the paper, and upstream water height H above the weir crest. If it is known that Q is proportional to b, use the pi theorem to find a unique functional relationship Q(g, b, H).

Answer 1

i) Reynolds number = Reynolds number (Re) is a dimensionless number used to depict the regime of flow in a channel i.e the flow is either laminar (Re<2300)or tranistion or turbulent flow(Re>4000)

Re= (vd/)

Froude number = Froude number (Fr) is also a dimensionless number used to depict the regime of flow in a open channel flow i.e either Subcritical (Fr<1) or critical (Fr=1) or supercritical (Fr>1).

Fr = V/√(gD)

ii)