Scaling-law-based decomposition and Reynolds-number effects of wall-bounded turbulent motions

Wall-bounded turbulence widely exists in nature and engineering, the in-depth study and understanding of which can help to develop new computational models and control methodology. Turbulence has multi-scale characteristics, and the anisotropy caused by the wall makes the multi-scale motions of wall turbulence more complex and challenging. This paper discusses and summarizes the scaling-law-based decomposition methods for wall-bounded turbulent motions, including inner-outer decomposition and outer decomposition. The inner-outer decomposition is based on the Reynolds-number independence of the inner turbulent motions, and the outer decomposition is based on the scaling laws of Townsend’s attached eddy hypothesis. Finally, the Reynolds number effect of the statistical characteristics of the wall turbulent motions after decomposition is discussed, and two critical Reynolds numbers are given for the inner turbulent motions to reach Reynolds number independence and for the appearance of the outer turbulent motions.