Question

Consider a source-less 3-D steady-state diffusion problem. The general discretized equation is aP ΦP = ∑anb Φnb. What is aP?

(a) aP=aW+aE+aS+aN+aT+aB

(b) aP=aW+aE+aS+aN

(c) aP=aW+aE+aS+aN+aT

(d) aP=0

I got this question in quiz.

Question is taken from FVM for Multi-dimensional Steady State Diffusion in section Diffusion Problem of Computational Fluid Dynamics

Answer 1

Correct answer is (a) aP=aW+aE+aS+aN+aT+aB

The best I can explain: For all steady-state diffusion problems, in the absence of source term, aP=∑anb. Therefore, for the three-dimensional case, aP=aW+aE+aS+aN+aT+aB which includes the coefficients of all the neighbouring flow variables.