What is it about?

Quantification of flow rate and pressures in a valveless pump consisting of two tubes of different compliance connected to a closed loop, incorporating a pinching mechanism that compresses periodically a part of the more flexible tube. It is the first time that in valveless pumping experiments there are four quantities simultaneously measured, namely: the pressures at the tube junctions, the flow rate and the compression of the tube. A new evidence is provided regarding the maximization of the mean flow rate, namely this happens when the pressure at the closer to the pincher tube junction increases in phase with the compression of the tube. A new evidence is provided showing that despite the general notion, when pinching takes place at the mid length of the tube non zero mean flow rates can be generated under certain conditions. Moreover, the flow rates jump from positive to negative values without going through zero when the pinching point crosses the mid length of the tube and the pinching frequency is close to the natural frequency of the hydraulic system.

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Why is it important?

Valveless pumping appears in the circulatory systems of many living species like in adult invertebrates with valveless hearts or malfunctioning heart valves, in the human during early embryonic life development where heart is valveless, in blood pumping due to the venules wall motion caused by the neighbored arterioles' wall interaction, in cerebrospinal fluid dynamics, etc. Moreover, organic fluid circulation in various simple animal species is performed through a valveless pumping process. Due to its simplicity, valveless pumping has been also applied recently in fabrication of micropumps, while is the major mechanism for blood circulation when cardiopulmonary resuscitation is applied in emergency conditions.

Perspectives

Due to the relative large dimensions of the examined pump system, and its small natural frequency at which valveless pumping is more effective, more quantitative details of the phenomenon are depicted. The geometry of the examined valveless pump is the one initially proposed by Liebau, namely a closed hydraulic loop in contrast to open systems-loops which are usually experimentally studied in literature. Moreover, the present work examines experimentally all the important involved parameters for a wide range of their values. All the above might provide assistance to the numerical or analytical modeling so that more realistic predictions of this multiparametric phenomenon could be obtained.

Dr CHRISTOS MANOPOULOS
National Technical University of Athens

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This page is a summary of: Net flow generation in closed-loop valveless pumping, Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science, February 2020, SAGE Publications, DOI: 10.1177/0954406220904110.
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