Question

DNS method is applicable for __________

(a) Complex geometry and low Reynolds number

(b) Simple geometry and low Reynolds number

(c) Simple geometry and high Reynolds number

(d) Complex geometry and high Reynolds number

The question was posed to me by my college director while I was bunking the class.

The question is from Direct Numerical Solution for Turbulent Models topic in portion Turbulence Modelling of Computational Fluid Dynamics

Answer 1

Right option is (b) Simple geometry and low Reynolds number

To explain I would say: The DNS method needs highly refined grids to capture the detailed flow. So, it is not suitable for complex geometries as it will make the system more complicated. As the Reynolds number increases, the number of grids and time-steps also will increase. This will lead to higher complexity again.