Question

In the given below figure of Mechanism of vacuum generation, point ‘2’ is the indication of _____

(a) Poynting point

(b) Vena contracta

(c) Stack point

(d) Steric point

The question was asked in unit test.

Question is from Aspiration Effect topic in division Pouring – Gating Design, Melting Furnaces, Melting and Casting Quality of Casting-Forming-Welding I

Answer 1

Correct answer is (b) Vena contracta

For explanation I would say: The constricted region at point 2 in the figure is known as vena contracta. A sudden change in the flow direction cause the aspiration effect and thus vacuum as the liquid metal stream contracts around a sharp corner due to the momentum effect. To avoid vacuum, the mould is made to fit the vena contracta.