Fractal Geometry of Round Turbulent Cryogenic Nitrogen Jets at Supercritical Pressures

摘要

Box-counting and EDM methods were used to measure the fractal dimension of round turbulent cryogenic nitrogen jets at pressures ranging from subcritical to supercritical pressures. Both method produced similar trends, with close quantitative agreement for a suitably small box-counting scale. At subcritical pressures, the fractal dimension was found to be consistent with the fractal dimension of a spray in the 2nd wind-induced atomization regime. The fractal dimension tended to increase as pressure increased, until at supercritical pressures the fractal dimension was found to be consistent with that of gas jets and mixing layers. The results constitute additional quantitative evidence for the hypothesis that subcritical jets exhibit mainly spray-like behavior, while supercritical jets exhibit mainly gas-like behavior. This appears to have been the first time pressure effects on the fractal dimension of turbulent jets has been measured.