THE PHENOMENON OF WAKES FORMATION AND DEVELOPMENT BEHIND LIQUID DROPLETS

Abstract

Numerical simulations of spherical; droplets sedimenting in a Newtonian fluid in an unbounded region were investigated by using finite element method for Reynolds number up to 300. The computations are thereby carried out with the penalty method instead of the integral method. The effect of the viscosity ratio n* in the range 0.02 < n* < 1000 and the density ratio p* in the range 0.02 < p* < 1000 on the wake formation and development was studied. It was observed that no wake is formed behind s droplet when the viscosity ratio n* is below 2.3. The critical Reynolds number for a droplet with fluid properties p* = 1 and n* = 50 and another droplet with fluid properties p* = 1000 and n* = 50 is the same, and is 28.5. The viscosity ratio thus has strong effect on wake formation while density ratio has an insignificant effect. Further results show that the wake length and the angle of separation depend very strongly on the viscosity ratio. The results are very useful for the design and optimization of engineering equipment where droplets occur.