Powder turbulence: direct onset of turbulent flow

(Received 27 July 1992, accepted in final form 9 September 1992)

Abstract
A vibrated bed of powder with a large aspect ratio (periodic boundary) is examined. In contrast to the bed with a small aspect ratio (with side wall), no clear convection roll is observed. The flow in the fluid phase seems to be always turbulent, because the local vibration of powder is static state has already become spatially random before the flow starts. This powder turbulence provides us with a new tool to study general hard turbulence.