Question

Why is Velocity of a fluid in contact with any solid surface is zero?

(a) Due to cohesive forces in the fluid particles

(b) Due to low velocity of fluid

(c) Due to no slip condition

(d) Due to high intermolecular forces between the fluid particles

This question was posed to me in homework.

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

Answer 1

Correct answer is (c) Due to no slip condition

The explanation is: Velocity of a liquid metal in the sprue and the gate is not uniform across the cross-sections. It is maximum at the axis of the conduit and zero at the solid surface due to high adhesive bonding between the surface and the fluid particles, which is responsible for viscosity and results in no slip condition.