Hierarchy of CFD Simulation Methods
A hierarchy of CFD simulation methods exists in which they are classified according to the physics they are capable of modeling. At the top of the hierarchy are direct
numerical simulation (DNS) techniques; at the bottom are panel methods. A rough guide to the members of the hierarchy and their respective abilities is provided in the following subsections.
14.6.1 DNS Simulation Technique
DNS is capable of simulating time-dependent turbulent flows, capturing the dynamics of the entire spectrum of eddy sizes. This requires grids and time steps that are finer than the length and time scales at which turbulent energy is dissipated. Low – diffusion numerical schemes are necessary. DNS is useful for supplementing experimental data and aiding the development of turbulence models, but it is prohibitively expensive at the flight Re numbers. It is not used in the design process. Currently, DNS is the most sophisticated method.