Numerical simulation of turbulent flow is of practical importance in geophysics and is useful as a test of turbulence theory. From a basic scale analysis of turbulent flow it is shown that complete simulation is only practicable for two‐dimensional or marginally turbulent three‐dimensional flows. Some examples of such simulations are described. A more useful approach for practical applications is to directly simulate the larger scales of motion and only consider the small unresolved scales with respect to their gross statistical interactions with the larger scales. A variable eddy viscosity model has proved useful for this purpose, although better approximations can be devised. Methods of discretization and numerical integration are discussed, and it is proposed that Galerkin methods are preferred when feasible in order to avoid truncation and aliasing err