Question

Which of the following reasons is the incorrect reason for frictional losses in the conduit?

(a) Gradual change in flow direction

(b) Sudden contraction of the flow cross-sections

(c) Sudden enlargement of the flow cross-sections

(d) Due to irrotational flow of molten metal

This question was posed to me during an interview.

The above asked question is from Effects of Friction and Velocity Distribution in section Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I

Answer 1

Right answer is (d) Due to irrotational flow of molten metal

Best explanation: In real fluids, the frictional losses are always present, especially when there is a sudden contraction or enlargement of the flow cross-sections and also due to a gradual change in the flow direction, e.g., in a 90° bend and similar other fittings.