Wall Layer Microturbulence Phenomenology and a Markov Probability Model forActive Electromagnetic Control of Turbulent Boundary Layers in an Electrically Conducting Medium

摘要

A thorough review of the published database on wall layer events and scales isconducted. Attention is focused on microturbulence phenomenology and the temporal and spatial scaling relationships of microturbulent events. The goal is to organize the comprehensive experimental database into a coherent framework for engineering applications to drag and noise control. The premise is that to effectively control the drag and noise in a turbulent flow, the methodology must address the genesis of the most fundamental elements of microturbulence. The Reynolds number dependence of useful parameters, such as the distance between bursts, distance between sweeps, combined ejection and burst duration, and sweep duration, is compared to verify consistency among published results on microturbulence investigations. The dynamic relationships of microturbulent burst power are derived from a heuristic perspective. On the assumption that an electromagnetic turbulence methodology can provide a remote pressure field into the flow at the normal distance from the solid surface where most of turbulence production takes place, the threshold Lorentz pressure power is derived. This derivation is based on the principle that the pressure must equal or exceed the local, natural, turbulent burst power level to have any appreciable effect on the turbulence production process. Expressions of the ratio of Lorentz power to natural microturbulent burst power in terms of the magnetohydrodynamic (MHD) interaction parameter and electrode and magnet spacing Reynolds number are derived. Similarly, the electrode and magnet spacing Reynolds number as a function of MHD interaction parameter and length Reynolds number at threshold condition is shown.