Hydrodynamic stability theory and wall turbulence

This paper discusses the role of hydrodynamic stability theory in understan ding wall bounded turbulent flows. Work in this area was pioneered by Malku s, followed by Reynolds and Tiederman and Reynolds and Hussain. The experim ental results, and theoretical cum computational results of Reynolds and Hu ssain, were significant in many ways. Mainly, they highlighted the behaviou r of organized disturbances introduced into the flow field, However, no con clusions could be reached, one way or other, regarding a definite connectio n between hydrodynamic instability and wall turbulence. More recently, and over the past few years, we have improved upon the theoretical analysis of Reynolds and Hussain and have also done some experiments. We are now able t o conclude much more positively that organized disturbances and hydrodynami c instability modes may have a very definite connection with wall turbulenc e. Here we present brief reviews of the past works of others and mainly sum marize our work and discuss some of our recent findings.