SUMMARY AND APPRAISAL OF SELF-SUSTAINING MECHANISMS IV*

In this paper we review and try to synthesize 6 papers on self-sustaini ng mechanisms of wall turbulence. The authors of these papers propose various models of the nearwall turbulence dynamics, including stochastic models, models based on truncations of eigenfunction expansions and conceptual models. It is noted that the conceptual models, which describe the structural features of the near-wall turbulence and the dynamic mechanisms that produce them, provide a remarkably consistent picture of near-wall turbulence. While these conceptual models need further testing, they are very promising. More quantitative models that might be useful for LES wall models or design of control schemes, seem less well established. But, there are certainly promising approaches, and one hopes that the recent progress on conceptual models will lead to progress on more quantitative models as well.