Design of a Cardiovascular Blood Flow Simulator and Utilization in Hemodynamic Evaluation of Mechanical Circulatory Support Devices.

PhDIncreasing numbers of old and sick patients who are no longer eligible for prolonged invasive implantation surgery have encouraged many researchers to investigate the development of a Mechanical Circulatory Support (MCS) device with more reliability and less possible invasive complications, which would benefit the majority of patients. This thesis will test experimentally and numerically the feasibility of installing an MCS device, as a bridge to destination, in the descending aorta, in a series configuration with the heart. To this end, a multi-chamber Simulator of the Cardio-Vascular blood-flow Loop (SCVL) was designed to simulate the in-vitro flow rates, pressures and other parameters representing normal and diseased conditions of the human cardiovascular system. The multi-chamber SCVL includes models for all four chambers of the heart, and the systemic as well as the pulmonic circulations. Next, a comprehensive study was conducted using the SCVL system to compare the novel in-series placement of the pump, in the descending aorta, with traditional in-parallel placements. Then, a comprehensive numerical study was conducted using the modified Concentrated Lumped Parameter (CLP) model developed by the same team. The numerical results are compared and verified by the experimental results under various conditions. The results for the pump installed in the descending aorta show that the pressure drop, upstream of the pump, facilitates the cardiac output as a result of after-load reduction. However, at the same time the generated pressure drop at the proximal part of the descending aorta induces a slight drop in the carotid perfusion which will be autoregulated by the brain in a native system. Further, the pressure rise downstream of the pump improves the blood perfusion in the renal artery. The pulse wave analysis show that the placement of the pump in the descending aorta leads to improved pulsatility which is beneficial for end-organ functionality in the native cardiovascular system

Experimental study of surface curvature effects on aerodynamic performance of a low Reynolds number airfoil for use in small wind turbines

This paper presents the wind tunnel experimental results to investigate the effects of surface gradient-of-curvature on aerodynamic performance of a low Reynolds number airfoil Eppler 387 for use in small-scale wind turbines. The prescribed surface curvature distribution blade design method is applied to the airfoil E387 to remove the gradient-of-curvature discontinuities and the redesigned airfoil is denoted as A7. Both airfoils are manufactured with high precision to reflect the design. Low-speed wind tunnel experiments are conducted to both airfoils at chord based Reynolds numbers 100 000, 200 000, and 300 000. Surface pressure measurements are used to calculate the lift and pitching-moment data, and the wake survey method is applied to obtain the drag data. The experimental results of E387 are compared with NASA Low Turbulence Pressure Tunnel (LTPT) results for validation. The gradient-of-curvature discontinuities of E387 result in a larger laminar separation bubble which causes higher drag at lower angles of attack. As the angle of attack increases the separation bubble of the airfoil E387 moves faster towards the leading edge than that of A7, resulting in a premature bubble bursting and earlier stall on E387. The impact of the gradient-of-curvature distribution on the airfoil performance is more profound at higher angles of attack and lower Reynolds number. The aerodynamic improvements are integrated over the 3D geometry of a 3 kW small wind turbine, resulting in up to 10% increase in instantaneous power and 1.6% increase in annual energy production. It is experimentally concluded that an improved curvature distribution results in a better airfoil performance, leading to higher energy output efficiency

In vitro cardiovascular system emulator (bioreactor) for the simulation of normal and diseased conditions with and without mechanical circulatory support

© 2013 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation.This article presents a new device designed to simulate in vitro flow rates, pressures, and other parameters representing normal and diseased conditions of the human cardiovascular system. Such devices are sometimes called bioreactors or "mock" simulator of cardiovascular loops (SCVLs) in literature. Most SCVLs simulate the systemic circulation only and have inherent limitations in studying the interaction of left and right sides of circulation. Those SCVLs that include both left and right sides of the circulation utilize header reservoirs simulating cycles with constant atrial pressures. The SCVL described in this article includes models for all four chambers of the heart, and the systemic and pulmonary circulation loops. Each heart chamber is accurately activated by a separate linear motor to simulate the suction and ejection stages, thus capturing important features in the perfusion waveforms. Four mechanical heart valves corresponding to mitral, pulmonary, tricuspid, and aortic are used to control the desired unidirectional flow. This SCVL can emulate different physiological and pathological conditions of the human cardiovascular system by controlling the different parameters of blood circulation through the vascular tree (mainly the resistance, compliance, and elastance of the heart chambers). In this study, four cases were simulated: healthy, congestive heart failure, left ventricular diastolic dysfunction conditions, and left ventricular dysfunction with the addition of a mechanical circulatory support (MCS) device. Hemodynamic parameters including resistance, pressure, and flow have been investigated at aortic sinus, carotid artery, and pulmonary artery, respectively. The addition of an MCS device resulted in a significant reduction in mean blood pressure and re-establishment of cardiac output. In all cases, the experimental results are compared with human physiology and numerical simulations. The results show the capability of the SCVL to replicate various physiological and pathological conditions with and without MCS.Peer reviewe