THE EFFECT OF SMALL PARTICLES ON FLUID TURBULENCE IN A FLAT-PLATE, TURBULENT BOUNDARY-LAYER IN AIR

This paper describes the result of both an experimental and an analytical investigation of the response of a two-dimensional, turbulent boundary layer in air to the presence of particles. Copper shot, 70-mu-m in diameter, were uniformly introduced into a vertical boundary layer, at a momentum thickness Reynolds number of about 1000. The particle mass flux was set at 20% of the fluid mass flux, and all measurements were made using a single-component, forward-scatter laser Doppler anemometer. The measurements clearly demonstrated that the particles damped fluid turbulence, apparently affecting all scales equally. The measurements further showed a strong correlation between the degree of damping and the particle concentration in the log region of the boundary layer.