An Approach for the Analysis of Collapse Onset in Elastic Tube Flows

An experimental study conducted for the determination of the onset of collapse of an elastic tube of a Starling resistor conveying air is presented herein. The collapse was induced under the action of external pressure p(e) applied to the tube walls. The influence of length L, thickness h, and modulus of elasticity E of the tube on collapse were determined by using a variety of silicone rubber and latex-Penrose tubes. The experiments were conducted under the presence of constant upstream head with the absence of a longitudinal strain of the tube in a range of flow Reynolds number (Re) 16750 < Re < 70280. At each air flow rate Q through the tube, p(e) was increased gradually. The inlet and exit pressures of the tubes p(1) and p(2) were measured. The variation of Q with p(e) was used to determine the onset of collapse. The magnitude of p(e) at the onset of collapse was defined as p(e,c). The visually observed collapse was associated with a flow rate reduction, followed by so-called oscillating and non-oscillating cases. The experimental data at the onset of collapse were expressed in terms of a correlation between Re (h/L) and a non-dimensional pressure parameter defined as (p(e,c) - p(2))/K-p including circumferential bending stiffness of the tube K-p.