Acceleration of a Liquid Drop Exposed to an Airstream

This paper describes the velocity and acceleration of a liquid drop exposed to an airstream. Experiments were conducted using a 60 mm×150 mm cross-sectional and 500-mm-long horizontal air-suction wind tunnel. Water was fed to a nozzle attached to a vibrator. Naturally dripping uniformly sized drops from the nozzle or uniformly sized liquid drops produced by a longitudinal vibration of the nozzle were used. Drops were exposed to airstreams and moved downstream. The prediction of the trajectory of droplets is useful for designing high-speed aircraft, combustion facilities, cooling facilities, etc. In order to predict the motion, the drag coefficient is required. However, the drag coefficient of a deforming liquid droplets has not been investigated sufficiently. To calculate the drag coefficient, the acceleration of a drop must be known. Therefore, in this experiment, the displacement and deformation of liquid drops exposed to airstreams were measured from photographs obtained by triple exposure photography or consecutive photography. From these data, velocity and acceleration of a drop exposed to airstreams were calculated.