A numerical study of the flow fields around a typical conical graupel falling at various inclination angles

摘要

Numerical calculations of the flow fields around falling conically shaped graupel have never been presented before and yet such fields are necessary for accurate assessment of many cloud physical processes. In this study, the flow fields around a typical conical graupel falling at Reynolds number 440 with inclination angles varying from 0 to 45° are investigated to understand how the inclined fall orientation influences the flow field properties around a falling conical graupel of typical size. We use the computational fluid dynamics software Fluent to solve the relevant time-dependent Navier-Stokes equations numerically to obtain various flow properties such as the velocity vectors, drag, vortex shedding frequency, pressure and vorticity. We show the computed flow fields around uninclined and inclined conical graupel, and demonstrate that Fluent can be used successfully for simulating flow past a falling conical body. We also found that the drag oscillates at a frequency of about 150 Hz and is the higher the more inclination of such graupel. The drag coefficient generally decreases with increasing inclination angle.