Analysis of gravitational settling regimes for a drop

The results of a study on the gravitational settling of water drops with a diameter of 0.5–5 mm in air are presented. A new setup for studying the characteristics of drop setting is tested. To obtain reproducible drops and to measure their sizes, the Mariotte bottle and gravimetric method are presented as the most appropriate. For Weber numbers We < 1.6, the patterns of drop setting correspond to a solid spherical particle. It is shown that the length of the non-stationary section of the drop trajectory increases linearly from 1 to 15 m with increasing the drop diameter. The approximation dependence for the distance traveled to reach a stationary settling regime is obtained. It is shown that Klyachko-Mazin formula is the most adequate for determining the drag coefficient in the range of Reynolds numbers Re = 0.3$ \div$ 700. The numerical calculation results are in quantitative and qualitative agreement with the experimental data.