Boundary conditions for turbulence simulation

Physically realistic, mathematically well-posed boundary conditions (BC) are needed to close the system of partial differential equations representing a turbulent flow. BCs play a key role in establishing physically meaningful simulations. There is an interplay between the choice and implementation of BCs and the underlying discretization method. It is important to ensure that any artifacts of discretization or numerical parameters have controllable impacts on the turbulence. The aims of this chapter are review strategies for posing BCs for the incompressible and compressible Navier–Stokes equations, and to arm the student with “good” boundary conditions, understand what the existing techniques can and cannot do, and to provide some tools for assessing their impact on the quality of the turbulence simulation.