DETERMINATION OF VELOCITY AND SIZE DISTRIBUTIONS OF SMALL FALLING WATER DROPS

A new method to measure the fall velocity of small water drops and an improved method to measure their size distribution are discussed ih th is paper. The oil-microscope method is an improvement over the oil met hod of Eigel and Moore (1983) to determine small water drop sizes and their distribution, while a newly developed videocamera method was use d to measure the fall velocity of small water drops. Both methods are simple and direct, and give quick and accurate results. The only equip ment required for the oil-microscope method is a standard optical micr oscope. This method is especially useful to measure the size of very s mall water drops (less than 0.5 mm in diameter), which is not easily a chievable by other methods. The smallest drop size measured in this st udy was 0.03 mn in diameter. The videocamera method requires only fair ly standard equipment (stroboscope, videocamera, monitor, and videocas sette recorder) and has the advantage of being appropriate for very sm all water drops. Both methods can be readily used either in the field or in the laboratory.