Multistability intermittency in an air-conveying soft tube

摘要

We analyze the intermittent regime which develops in an air-conveying soft tube. The very thin walls of the tube allow the pipe to fluctuate with high amplitudes and to exhibit kinks in its shape. As a consequence, the flow pressure alternates between turbulent and laminar phases. In the experiment the turbulent phase durations scale exponentially while the laminar phases display algebraic statistics. The coexistence of these two distinct laws for the same value of the control parameter value can be modeled on the basis of two competing stochastic processes with different time scales. The first one refers in our case to the local flow velocity and the other one is a critical velocity related to the tube geometrical variable shape which is quenched during the laminar phases but rapidly varying during the turbulent phases. The model reveals that the modification of the ratio eta between these two time scales changes the duration distributions from the exponential shape in turbulent phases to algebraic in laminar phases. The interesting experimental observation is the existence of several different laminar states for any fixed control parameter value of the system which do not correspond to a vertical straight shape of the tube. We describe the statistical characteristics of such states and propose an interpretation of them on the grounds of the theoretical model. (C) 2019 Elsevier B.V. All rights reserved.