NUMERICAL STUDY OF THE MAXIMUM BOUNDARY SHEAR-STRESS INDUCED BY RAINDROP IMPACT

The magnitude, position, and timing of the instantaneous maximum boundary shear stress caused by a raindrop on a shallow pool of water are investigated using a series of computer simulation experiments in which the Navier-Stokes equations are solved numerically. A dimensional analysis defines a set of parameters involving fluid properties and initial conditions relevant to the problem. Numerical simulations are performed over ranges of these parameters using a generic, two-dimensional, incompressible, free surface flow model. Results of the simulations are summarized in simple algebraic relationships which serve to clarify the relative importance of the parameters. The algebraic relationships also serve as an efficient substitute for the numerical model in the estimation of the magnitude, position, and timing of the maximum boundary shear stress. Laboratory measurements of water-droplet-induced shear stress are used to demonstrate the validity of the algebraic relationships.