Consider incompressible flow in a circular channel. Derive general expressions for Reynolds number in terms of

(a) volume flow rate and tube diameter and

(b) mass flow rate and tube diameter. The Reynolds number is 1800 in a section where the tube diameter is \(10 \mathrm{~mm}\). Find the Reynolds number for the same flow rate in a section where the tube diameter is \(6 \mathrm{~mm}\).