Transient Study of Flow and Cavitation Inside a Bileaflet Mechanical Heart Valve

Abstract

A mechanical heart valve (MHV) is an effective device to cure heart disease, which has the advantage of long life and high reliability. Due to the hemodynamic characteristics of blood, mechanical heart valves can lead to potential complications such as hemolysis, which have damage to the blood elements and thrombosis. In this paper, flowing features of the blood in the valve are analyzed and the cavitation mechanism in bileaflet mechanical heart valve (BMHV) is studied. Results show that the water hammer effect and the high-speed leakage flow effect are the primary causes of the cavitation in the valve. Compared with the high-speed leakage flow effect, the water hammer has a greater effect on the cavitation strength. The valve goes through four kinds of working condition within one heart beating period, including, fully opening stage, closing stage and fully closing stage. These four stages, respectively, make up 8.5%, 16.1%, 4.7% and 70.7% of the total period. The cavitation occurs on the fully closing stage. When the valve is in closing stage, the high pressure downstream of the valve lasts for about 20 ms and the high-speed leakage flow lasts for about 200 ms. This study systematically analyzes the causes of cavitation emerged in the process of periodic motion, which proposes the method for characterizing the intensity of the cavitation, and can be referred to for the cavitation suppression of the BHMV and similar valves.The main concerns of valve research have been the performance [3] and the internal flow properties [4]. In order to study the hydrodynamic characteristics of the mechanical heart valve, numerical simulation based on CFD is one powerful tool to study cardiovascular risk factors, especially those related to mechanical properties of artificial heart valve [5]. It is an effective way to improve the performance of the valve by structure optimization, which is applicable to many valves +(e.g., Tesla valve) [6,7], and the BMHV is no exception. Many works on the effect of geometric features of the BMHV on blood stream are performed by simulations in the past years. For example, it has been found that the maximum shear stress within the range of platelet activation can lead to thrombosis [8,9]. The strategy of self-adapting mesh is used to capture the motion of the leaflet realizing by user-defined functions (UDF) in the commercial software [10]. It is found that the valve leaflet and the valve pivot are continuously exposed to shear stress higher than 52.3 Pa, which can cause damage to the platelets. The problem of thrombosis can be solved by increasing the curvature of the leaflet of the bileaflet mechanical heart valve [11]. Results show that increasing the curvature of the leaflet can provide larger central circulation area and reduce the risk of thrombosis. Another way [12] is proposed by using BMHV with SH coating to reduce the interaction between blood and BMHV. Based on effect analysis of BMHV with SH coating on blood substances and hemodynamics, the performance index of BMHV with SH coating, w...

Comparison of Swing and Tilting Check Valves Flowing Compressible Fluids

“…To investigate the dynamic characteristics of check valves, the common methods used by other researchers are the fluid–solid interaction (FSI) method, the dynamic mesh method [ 21 , 22 , 23 ], and the weighted-essentially non-oscillatory (WENO) method [ 37 , 38 ]. The dynamic mesh method is adopted in this study to solve the opening period of check valves.…”

“…Li et al [22] used CFD methods to study the mechanism of cavitation in a bileaflet mechanical heart valve, which is a type of check valve. Lai et al [23] focused on the opening period of a dual disc check valve using CFD and experimental methods, and they proposed a correlation to estimate the start and endpoints of disc rotations. Farrell et al [24] proposed a method to calculate the required flow rate to achieve the fully open state or an intermediate opening of check valves, and their results can reduce the simulation work.…”

Numerical Study of the Microflow Characteristics in a V-ball Valve

“…Li et al [ 6 ] studied the cavitation suppression method in a globe valve with a valve cage. Li et al [ 7 ] and Qian et al [ 8 ] focused on the cavitation inside a mechanical heart valve. Sreekala and Thirumalini [ 9 ] found that the sound pressure level could be reduced by adding the flow passage numbers in the valve cage of a globe valve.…”

Statistical Characteristics of Flow Field through Open and Semi-Closed Bileaflet Mechanical Heart Valve

“…Therefore, for patients with such valves, life-long anticoagulation therapy is necessary [1,2,17,32,33]. These defects are caused by the non-physiological dynamics of the blood flow through the valve, the rigidity of the valve leaflets, the formation of intense vortex and jet flows, and the increased shear stresses [34][35][36]. Intensive backflows are formed in the gaps of the hinged joints of the leaflets and the base of the valve, which destroy the red blood cells and platelet shells.…”

“…Intensive backflows are formed in the gaps of the hinged joints of the leaflets and the base of the valve, which destroy the red blood cells and platelet shells. Here thrombi are formed, which are attached to the valve leaflets in the area of stagnant flows near the hinged joints [2,34,37,38]. Cavitation areas with microbubbles in the blood flow are formed, during the closing of the leaflets of the mechanical valves due to a sharp decrease in pressure.…”