A numerical study on the ventilation coefficients of falling lobed hailstones

Abstract

The ventilation coefficients that represent the enhancement of mass transfer rate due to the falling motion of spherical hailstones in an atmosphere of 460hPa and 248K are computed by numerically solving the unsteady Navier‐Stokes equation for airflow past hailstones and the convective diffusion equation for water vapor diffusion aroundthe fallinghailstones.The diameters of the hailstonesinvestigated are from 1to 10cm, corresponding to Reynolds number from 5935 to 177148. The calculated ventilation coefficients vary approximately linearly with the hailstone diameter, from about 19 for a 1-cm hailstone to about 208 for a 10-cm hailstone. Empirical formulas for ventilation coefficient variation with hailstone diameter as well as Reynolds and Schmidt numbers are given. Implications of these ventilation coefficients are discussed.