An analytical and experimental study on dynamics of Newtonian falling drops in inertia regime with low Reynolds numbers

Two phases flows particularly motion droplets into a second fluid have variety of application in different industries including oil and gas industry, medicine and pharmaceutical, extraction of metals, power plants as well as heat exchangers. In this paper, dynamic of a Newtonian drop falling in laminar regime is studied. A fluid which its viscosity is 340 cP is used in order to produce an inertia flow. In experimental section, de-ionized water and glycerin solutions with volume concentrations of 21:79 and 17:83 are used for drop phase. By increasing the volume of drop that leads to rising the inertia force, the drop shape is changed from spherically and a dimple at the rear of drop is appeared. Inertial forces, surface tension and hydrodynamic tension play a significant role on drop shape. Increasing the drop volume causes expanding the dimple consequently drag force is enhanced and terminal velocity of drop is decreased as well. According to the experimental observations, variations of viscosity ratio does not have a profound effect on drop deformation. Moreover, increasing the Reynolds number leads to reduction of pressure coefficient. It is shown that the experimental observations have an appropriate agreement with analytical results.