Boundary shear stress induced by raindrop impact

Abstract

An efficient mathematical model for calculation of the boundary shear stress field induced by raindrop impact is developed and tested using numerical and experimental data. The model comprises a series of dimensionally consistent, closed-form, algebraic equations, written in terms of physically meaningful parameters describing the fluid properties and initial conditions at the instant of drop impact. The relationships in the model are derived from the analysis of data generated by a computer code which numerically solves the Navier-Stokes equations for two-dimensional flow of a viscous, incompressible fluid with a free surface. The resulting simplified, algebraic model is validated using data from laboratory experiments which employ hot-film anemometry to measure drop induced boundary shear stresses. Substantial agreement is found between model and experimental results with regard to the boundary shear stress magnitudes and sensitivity of magnitudes to different water layer depths, drops sizes, drop veloc...