(242d) Shape of a particle curtain falling in stagnant air

The dynamics of a free falling particle curtain have been analysed and studied in the laboratory. In the experiments a steady, uniform, high-voidage stream of particles was fed through a rectangular slit to form a curtain across the entire width of a horizontal duct of cross-section of 15 x 60cm. The thickness of the particle stream at the inlet was varied over the range 20 ? 100 mm by varying the width of the rectangular slit. The particle flow rates were maintained in the range of 35g/s to 37g/s. The shape of the curtain and trajectory of the particles were recorded using a high-speed video camera. Our results indicate a low voidage curtain leads to diverging curtain; increasing the initial voidage of the particle stream causes the curtain to become less divergent; further increase the voidage of the particle stream causes the curtain to become increasingly convergent. A simple model for the phenomenon is suggested.