Stability of Liquid Flow Down an Inclined Tube

A linear stability analysis has been performed to investigate the stability of liquid flow down an inclined circular tube. To this purpose, approximate solutions which describe laminar and turbulent steady flow down an inclined tube have been developed first. The stability analysis has then been performed by an integral method. The results of the present investigation indicate that, in general, flow in a tube is more stable than in a channel and, in particular, there is a value of the liquid height at which the flow is always stable.