Question

An extra grid is used before the physical boundary. What is the use of this grid?

(a) To store the inlet boundary values

(b) To solve the discretized equation

(c) To calculate the inlet boundary values

(d) To solve the system analytically

The question was posed to me in an online interview.

The doubt is from Boundary Conditions topic in section Boundary Conditions of Computational Fluid Dynamics

Answer 1

Right choice is (a) To store the inlet boundary values

Explanation: The grid extends outside the physical boundary and these nodes are used to store the inlet variables. The discretized equation is solved starting from the first internal cell.