Drop/Gas Interactions of Dense Sprays

Abstract

Abstract : Two processes of dense sprays are being studied: (1) turbulence modulation, which involves the turbulent field generated by drop motion; and (2) secondary drop breakup which can be the rate controlling process in dense sprays. Since past work on turbulence modulation highlighted the need for information on drop wake properties for low drop Reynolds numbers (10-1000), measurements of these flows are in progress using spheres traversing in stagnant glycerol baths. Three wake regions have been identified: a fast-decaying wake (caused by eddy shedding at drop Reynolds numbers greater than 200), a turbulent wake (extending to wake Reynolds numbers of 5-8), and a final laminar wake. Turbulence is not highly developed in the turbulent wakes, yet mean velocities satisfy similarity theory quite well. Current work is concentrating on results at higher Reynolds numbers, to approach results in the literature; studying wakes in turbulent environments; and introducing these results into a stochastic theory of turbulence modulation. Secondary drop breakup is being studied in a shock tube using water, glycerol and n-heptane drops. A breakup regime map has been developed, defining no-deformation, oscillatory deformation, non- oscillatory deformation, bag breakup, multimode breakup and shear breakup regimes as a function of Weber and Ohnesorge numbers. Results at Ohnesorge numbers greater than 4 show that these conditions are dominated by the no- deformation regime. Current work involves measurements of the dynamics and outcomes of bag and multimode breakup.