Mean rise rate of droplets in isotropic turbulence

This paper investigates the rise rate of droplets that are slightly lighter than the surrounding fluid. We experimentally investigate the effect of three parameters: Stokes number, turbulence intensity, and droplet Reynolds number. Droplets were injected into a chamber with nearly isotropic turbulence and little mean flow. The results show that at high turbulence intensity, the mean droplet rise rate is 25% of the root-mean-square velocity regardless of the Stokes number, while at low turbulence intensity, the droplets rise at a rate equal to the rise rate in a quiescent fluid. At intermediate turbulence intensity, the rise rate is strongly dependent on the Stokes number. Qualitative discussions explain these trends. (C) 2002 American Institute of Physics.