Shape of a particle curtain falling in stagnant air

The dynamics of a free falling particle curtain were 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 0.15 ?? 0.60 m. The thickness of the particle stream at the inlet was varied over the range 2a??10 cm by varying the width of the rectangular slit. The particle flow rates were maintained constant at approximately 0.040 kg/s. The shape of the particle curtain was recorded using a high-speed video camera. Our results indicated a low voidage curtain led to diverging curtain; increasing the initial voidage of the particle stream caused the curtain to become less divergent; further increase the voidage of the particle stream caused the curtain to become increasingly convergent. The shape of particle curtain was analysed using an Euleriana??Eulerian computational fluid dynamics (CFD) model. Reasonable agreement was found between the experiments and the CFD model predictions.