DENSITY-MEASUREMENTS ON LEVITATED LIQUID-METAL DROPLETS

Electromagnetic levitation is a useful tool for measuring thermophysic al properties of high-temperature melts such as liquid metals. Due to its noncontact nature, the undercooled regime is also accessible. Dens ity and thermal expansion of a levitated drop can be derived from volu me measurements, if its mass is known. Assuming cylindrical symmetry, the volume of a drop can be determined from its cross section. Using p hotography, such measurements on liquid metals have been performed in the past. Here we present an improvement of this method, which replace s the photographic camera with a CCD videocamera and subsequent digita l image processing. This reduces the time effect required to obtain th e results and allows one to average over disturbing surface oscillatio ns. The specific problems of digital image processing, namely resoluti on and edge detection, are addressed and results on nickel are present ed.