Abstract
Impedance pumping is a mechanism that generates flow in a compliant vessel by repeatedly actuating the vessel asymmetrically, without employing any internal valves, blades, or other mechanisms. The net flow is obtained by establishing a constructive wave pattern. Elaborate studies of impedance pumping in a single vessel have shown that the flow rate strongly depends on the actuation frequency, as well as on other parameters, such as actuator location and amplitude, and that it operates best in the resonance mode. The present study extends these principles to a network of multiple compliant vessels, representing a cardiovascular system. The flow is modeled numerically by the one-dimensional approximation of the Navier-Stokes equations. Two configurations were examined, systems consisting of three and five compliant vessels. First, the natural frequencies of these configurations were identified. Then, the dependence of the net flow rate (NFR) on the actuating frequency was explored, showing that impedance pumping operates best in the resonance mode in the case of a network of vessels as well. The impact of other parameters were studied as well, such as the location of one or two actuators, actuation amplitude, actuator width, the duty cycle, and the phase lag between the actuators. The results show that impedance pumps can generate significant NFR and the obtained NFR can be manipulated by properly setting up one or more of the governing parameters. These findings indicate that impedance pumping principles may be applied to flow control of the cardiovascular system.
Highlights
Impedance pumping is a technique to generate, augment, or manipulate flow and/or pressure head in an elastic vessels connected at the edges to vessels with different elastic properties [1,2]
The interest of the present study is in the net flow rate (NFR) generated by the multi-vessel impedance pump operating at zero pressure drop
Significant NFR is obtained only when the pump is operating in resonance mode
Summary
Impedance pumping is a technique to generate, augment, or manipulate flow and/or pressure head in an elastic vessels connected at the edges to vessels with different elastic properties (usually to rigid vessels) [1,2]. Experimental studies of impedance pumping in closed loop configurations [1,4,7,8] or in open loop configurations [3,7,9] show that for a certain set of parameters, pulsatile flow with significant NFR can be obtained. Using various actuation characteristics (such as actuator position, frequency, and size), a variety of conditions were presented under which pumping in a flexible tube occurs In these studies three basic conditions were identified for the net flow to exist in the loop [4]. A numerical simulation solving the 1D version of the Navier-Stokes equations was carried out They demonstrated that several actuators working close to the natural frequencies and having the appropriate phase delay between them can produce a relatively high net flow rate, even for very small actuation amplitudes.
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