A theoretical and experimental study of an oscillatory flow through a compliant tube

This paper presents a theoretical and experimental study of oscillatory flow through a finite compliant tube, aiming to investigate fluid-structure interactions in structures like blood vessels. The setup consists of a horizontally submerged polydimethylsiloxane tube mounted between two fixed ends, each instrumented with a pressure sensor. The device that provides the flow was custom-designed and manufactured by our team. It consists of two rigidly connected piston-cylinder assemblies that operate 180° out of phase, ensuring that the amount of fluid pushed into the tube from one end is identical to the amount pulled out from the other end, thereby making the flow purely oscillatory. Visualizing the flow inside a narrow tube with a constantly changing shape can be quite cumbersome, making corrections for light refraction distinctly challenging. Therefore, the tube's undulating shape is monitored using a high-speed camera. The instantaneous tube profile is obtained by processing the video offline in MATLAB. A theoretical model was developed to describe the tube's wall radial motion. The resulting equation was solved analytically for small deformations to obtain the predicted local deformation history. For radial deformations within ∼7%, the analytical solution agreed well with observation. Driven by this validation, a complete solution for the flow field is proposed within the small deformation limit. This study showcases a setup where a compliant tube's flow conditions are measured in tandem with its deformation, offering a unique avenue through which the fluid-structure interaction models in compliant tubes can be tested and refined.