Experimental Study of Resonant Interactions of Instabilitywaves in an Airfoil Boundary Layer

Abstract

The present paper is devoted to the detailed experimental study of weakly nonlinear resonant interactions of Tollmien-Schlichting waves in a specially designed 2D non self-similar boundary layer on an airfoil. The influence of the fundamental frequency on the efficiency of the tuned subharmonic resonance is investigated as well as the influence of frequency and spanwise wavenumber detunings. The results are compared with Direct Numerical Simulations based on a vorticity-velocity formulation of the complete Navier-Stokes equations. Good overall agreement is achieved.

Weakly nonlinear stages of boundary-layer transition initiated by modulated Tollmien–Schlichting waves

“…Again, few modes were introduced, and therefore the role of the modulation itself could not be clarified. The first results of the influence of different modulation Weakly nonlinear stages of transition initiated by modulated TS waves 577 frequencies were obtained by de Paula et al (2009) using an improved experimental set-up of Sartorius et al (2006), but only a rough description of the physical mechanisms was given there.…”

“…Indeed, the variation of the local Hartree parameter should, in principle, be able to affect strongly the efficiency of the resonant interactions of instability waves, and lead to either their enhancement (less probable) or their suppression (very probable). The only experimental results devoted to a systematic investigation of resonant TS wave interactions in boundary layers of aerofoils were published by Sartorius et al (2006) and recently compiled by Würz et al (2012a,b). It has been shown in a combined experimental, theoretical, and numerical investigation by Würz et al (2012a) that even strong non-self-similarity of the boundary-layer flow on an aerofoil is unable to suppress or delay resonant interactions.…”

“…The investigated regimes of disturbance excitation covered basically the range of subharmonic resonances within simple frequency triplets, with the participation of either exact subharmonic modes or those with frequency-detuned quasi-subharmonics or with spanwise-wavenumber-detuned subharmonic wave pairs. Only one preliminary test of the possibility of resonance superposition was made by Sartorius et al (2006). Again, few modes were introduced, and therefore the role of the modulation itself could not be clarified.…”