Experimental study of spinning granular jets

In this work the nature of noncohesive granular material flowing out of a rotating vertical pipe under the influence of gravity to form a free granular jet is examined. We analyze systems with different angular velocities $\Omega$ and found that the jet radius increases with both $% \Omega $ and the downward coordinate $z$. Experiments show that a no-flow condition is achieved for a critical angular velocity, $\Omega _ {c}$. Analytical solutions for the shape of the jet and $\Omega _{c}$ are in good agreement with experiments.