A numerical analysis is presented of free surface profiles, Marangoni conve
ction and the temperature distribution in electrostatically levitated dropl
ets. The analysis is based on the boundary element solution of electric pot
ential outside the droplet, the weighted residuals formulation of the free
surface balance equation involving electrostatic stresses, surface tension
and gravity, and the finite element solution of the internal fluid flow and
temperature distribution in the electrostatically deformed droplets. Numer
ical simulations are carried out for several different materials and variou
s operating conditions. Results show that an applied electrostatic field ge
nerates a normal stress distribution along the droplet surface, which, comb
ined with surface tension, causes the droplet to deform into an ellipsoidal
shape in microgravity and into the shape of a blob with the lower side bei
ng flatter under terrestrial conditions. Laser heating induces a non-unifor
m temperature distribution in the droplet, which in turn produces recircula
ting convection in the droplet. For the cases studied, Marangoni convection
is the predominant mode and buoyancy effects are negligible. It is found t
hat there is a higher temperature gradient and hence stronger Marangoni con
vection in droplets with higher melting points which require more laser pow
er. The internal recirculating flow may be reduced by more uniform laser he
ating. During undercooling of the droplet with heating turned off, both tem
perature and fluid flow fields evolve in time, such that the temperature gr
adient and the tangential velocities along the droplet surface subside in m
agnitude and reverse their directions. (C) 2000 Elsevier Science Ltd. All r
ights reserved.