| Abstract: | The flow fields of hexagonal ice plates and broad-branch ice crystals fallingin the air with Reynolds numbers from 20 to 140 were investigated by numerical simulations. The three-dimensional incompressible, unsteady Navier-Stokes equations for flow past fixed targets were solved by a second-order QUICK numerical scheme. Several velocity fields are displayed. It is shown that unsteady flow can be modeled by adding an artificial disturbance at a certain point. Computations showed that thin oblate spheroids are good approximations to hexagonal plates of the same size in the drag calculation whereas the broad-branch crystals are significantly different. Empirical formulas for drag coefficients were developed for cloud physical calculations. |
