A Numerical Study on the Attitudes and Aerodynamics of Freely Falling Hexagonal Ice Plates

Abstract

he fall attitudes and the flow fields of falling hexagonal ice plates are studied by numerically solving the transient incompressible Navier?Stokes equation for flow past ice plates and the body dynamics equations representing the 6-degrees-of-freedom motion that determine the position and orientation of the ice plates in response to the hydrodynamic force of the flow fields. The ice plates investigated are from 1 to 10 mm in diameter, and the corresponding Reynolds number ranges from 46 to 974. The results indicate that the 1-mm plate generates a steady flow field and exhibits a steady motion, whereas the rest of the ice plates generate unsteady flow fields and exhibit unsteady motions, including horizontal translation, rotation, and axial oscillation. The horizontal translation is primarily determined by the inclination due to oscillation. The pressure distributions around the falling plates are examined and discussed in association with the oscillation. The vortex structure in the wake of the plate is examined. Empirical formulas for fall speed, oscillation frequency, and drag coefficient are given. Potential impacts of the fall attitudes and flow characteristics on the microphysics of ice plates are discussed.