Vladimir I. Borodulin

Experimental study of resonant interactions of modulated waves in a non self-similar boundary layer

The current work is devoted to the study of weakly non-linear interactions of Tollmien-Schlichting waves in an incompressible, 2D airfoil boundary layer. Selected resonant regimes are investigated with emphasis to the regimes where more than one fundamental T-S wave are present in the flow. The results show that amplification rates of the effective sub-harmonic modes are not affected by modulations in time of the fundamental wave. It is also shown that modulations of the 2D fundamental waves tend to generate additional modes at modulation frequency. Furthermore, these modes can resonate with the fundamental ones as detuned subharmonics. This mechanism seems to be responsible for the initial seeds of subharmonics in cases of ‘natural’ transition.

On properties of the deterministic turbulence and reproducibility of its instantaneous and statistical characteristics

As known from previous studies, the deterministic turbulence (DeTu) is a post-transitional flow that is turbulent according to the generally accepted statistical characteristics but possesses, meanwhile, a significant degree of determinism, i.e., reproducibility of its instantaneous structure. It is found that the DeTu can occur in those cases when transition is caused by convective instabilities; in boundary layers, in particular. The present paper is devoted to a brief description of history of discovering the DeTu phenomenon, as well as to some recent advance in investigation of instantaneous and statistical properties of such turbulent boundary layer flows.