What shape are raindrops? Why do raindrops have this shape?

When there is no force or the raindrops are small, the raindrops will shrink and appear spherical; When subjected to external force, the windward surface of raindrops will flatten, and the rear end will remain spherical, showing the shape of upper circle and lower flat. Generally speaking, with the increase of diameter, the shape of raindrops gradually changes from round to oval, and then from oval to convex at the top and flat at the bottom. If the raindrops are too big, they will be deformed or broken.

When raindrops fall, they are affected by three forces: internal intermolecular force, gravity and air resistance. The intermolecular forces inside raindrops tend to form spherical water droplets; Gravity accelerates the overall fall of raindrops, but does not affect their shapes; Air resistance is more complicated, so let's focus on it.

Semi-quantitatively speaking, the direction of air resistance is opposite to the falling speed of raindrops. When there is no wind, the speed of raindrops rises linearly. When the raindrop speed is small, the resistance is proportional to the speed, F=-k? Five; When there is a vortex behind the speed, the resistance is approximately proportional to the square of the speed, F=-K? v？ ，K？ And k? Are all proportional factors. In both cases, the influence of air resistance on the shape of raindrops is similar. Raindrops form an obtuse angle on the windward side (below) and a gradual change on the leeward side (above). This shape minimizes air resistance, which is the shape of ordinary raindrops. In shipbuilding, in order to reduce air resistance, similar round and blunt bows are often built. Raindrops are actually "deformed" by clouds. There are many cloud drops in warm clouds with cloud temperature higher than 0℃.

Low speed, slow rising speed; However, Xiaoyun falls slowly and rises quickly. Therefore, this difference in relative motion is rapid. Big cloud drops will have a chance to collide with small cloud drops, and small cloud drops will become big cloud drops. Due to the uneven diffusion of updraft and seepage in the cloud, large cloud droplets can move around the cloud many times, which improves the probability of collision between large and small cloud droplets. When the big cloud drops become bigger and bigger, they will fall in the form of raindrops.

Generally speaking, with the increase of diameter, the shape of raindrops gradually connects from ring to ellipse, and then becomes flat from ellipse to top and bottom. When raindrops become too big, they will deform or break. According to the shape of raindrops with different sizes, precipitation can be accurately measured, and then weather conditions can be predicted, and disaster temperature points can be predicted in advance to make preparations, which can also be applied to water conservancy and eco-environmental protection industries. Therefore, the scientific research on the shape of raindrops is very important, and there are special research scientists in the process of studying science.