Heuristic Turbulence Modelling
The mathematical basis of the equations for electrically nonconducting flows is firm as long as they are applied to phenomena with fluid velocity much lower than light speed. In this sense, the numerical simulation (experiment) of these equations seems most suitable for the exploration of flow properties. In the study of turbulent flows encountered in engineering and scientific phenomena, however, the feasibility of the approach is not so large. Such a situation arises from a great number of spatial scales included in turbulent flows at high Reynolds numbers, as will be discussed below in a quantitative manner.