Flow filling a curved pipe

A small scale experiment was designed to study the propagation of the front of a viscous fluid filling a curved pipe. Several Newtonian fluids with di fferent viscosities and a non-Newtonian fluid have been used. The experimen ts show, that there exists a minimum speed for completely filling the pipe, which depends on the parameters of the experiment (diameter d and radius o f curvature R of the pipe, kinematic viscosity nu, of the fluid). Appropria te dimensionless numbers are introduced to characterize the flow and optima l filling conditions.