Near wake of a circular cylinder submitted to blowing - II Impact on the dynamics

The near wake of a porous circular cylinder in cross-flow submitted to blow ing through its whole surface is experimentally studied. The blowing impact on the Strouhal number exhibits a linear decrease of the vortex shedding f requency with the blowing ratio. A simple model representing this decrease as a function of the injection rate is developed, based on the wake static pressure profile evolution. The main flow temperature influence is also inv estigated in case of non-isothermal blowing and is shown to have no effect on the Strouhal number evolution. Finally, the interaction between the blow ing and the shear layer is investigated through a spectral analysis of the velocity signal. A modification of the shear layer power spectrum is observ ed when injection occurs. The dynamics are slowed down and characteristic p atterns, denoted sub-peaks, appear while the relationship between the von K arman and the shear laver frequencies without blowing remains valid. (C) 20 01 Elsevier Science Ltd. All rights reserved.