An investigation of the topography and motion of the turbulent interface

The sharp interface which exists in unbounded turbulent shear flows was studied using a linear array of twenty hot-wire probes. The probe arrangement was such that the location of the interface could be monitored instantaneously. The particular flow examined was a two-dimensional turbulent wall jet. It was found that the interface is a highly contorted surface which exhibits a significant amount of folding. Quantitative methods for characterizing this behaviour are presented, together with pertinent measurements. In addition, measurements of the mean surface area of the interface, and space-time corrrelations of the width of the turbulence were obtained. The latter were used to find characteristic scales and convection velocities of the interface.