OBSERVATIONS REGARDING COHERENCE AND CHAOS IN A MODEL OF TURBULENT BOUNDARY-LAYER

In the following, the present authors comment on a paper by Zhou and S irovich (ZS) [Phys. Fluids A 4, 2855 (1992)] which contained a critica l appraisal of the models developed by Aubry et al. (AHLS) [J. Fluid M ech. 192, 115 (1988)]. It is found that ZS's suggestion to use ''a ful l channel interpretation of wall eigenfunctions,'' thereby avoiding bo undary terms, while attractive mathematically, is questionable in flui d mechanical terms. A major point of AHLS's study was precisely to iso late the wall region and use the boundary terms to investigate the int eraction with the outer flow. Also, it is demonstrated that certain in stances of ''irregular'' bursting, as reported by ZS, are probably num erical effects.