Question

Which of these equations is the starting point of the DNS method?

(a) Continuity and momentum equations of homogeneous turbulent flow

(b) Continuity and momentum equations of incompressible turbulent flow

(c) Momentum and energy equations of incompressible turbulent flow

(d) Momentum and energy equations of homogeneous turbulent flow

This question was posed to me during a job interview.

My enquiry is from Direct Numerical Solution for Turbulent Models topic in chapter Turbulence Modelling of Computational Fluid Dynamics

Answer 1

Right choice is (b) Continuity and momentum equations of incompressible turbulent flow

Easiest explanation: The instantaneous continuity and Navier-Stokes equations (momentum equations) for an incompressible turbulent flow form the initial point of the Direct Numerical Solution method. These equations form a closed set of four equations with the four unknowns (pressure and three components of velocity).