Abstract: Aiming at the issue of the random motion characteristics of water droplets in a wind field, we formulate a hypothesis that the steady-state deformation of water droplets is ellipsoidal, and uses white noise to describe the randomness of the windward area caused by changes in relative wind speed and water droplet motion posture. A stochastic differential equation is worked out for the motion of ellipsoidal water droplets; their motion shape and drift distance are tested to verify the correctness of this new model. We apply it to calculations of the dispersion coefficients of water droplets under different conditions. The results show that for ellipsoidal droplets in motion, their random effects－produced by the random forces of a large number of air molecules and the changes in their windward area－are directly proportional to their Froude number.

Key words: flood discharge atomization, ellipsoidal water droplets, windward area, stochastic differential equation, noise intensity