A Calculation Formula of the Terminal Velocity of Water Drops in the Atmosphere

In this paper, for the terminal velocity v of a spheric water drop (with a radius r) falling in the fluid medium, an analytical solution is theoretically derived. The constants a and b in the formula are determined by the experimental velocity data of water drops in the atmosphere: a =0.53563, b=1.37358 with a maximum relative calculating error of 24%. This semi=theoretical formula is compared with the other empirical formulas. Three new statistical formulas in the form of are recommended. They divided r (0~2900μm) into 3,4 and 5 ranges with a maximum relative error of 11%, 7% and 4%, respectively