An investigation of flow structure in an artificial heart ventricle

Abstract

In order to improve AV construction, it is necessary to solve a series of bioengineering problems, including the optimization of AV geometry and the selection of artificial heart valve (AHV) orientation in the AV. Toward this goal, a series of studies were conducted concerning flow structure in model AVs, covering among other things, planar models [6], glass models [5], a specially prepared AV (optical knife method) [3], during orientation of an AHV disk on the AV membrane (optical polarization method) [6], and on AV output [2]. From the viewpoint of the authors, practical interest has focused on the investigation of flow structure throughout the volume of actually utilized AVs [4] with a series of AHVs in order to provide fabrication recommendations leading to the improvement of existing and workable AV and AH constructions. Visualization studies of flow structure were carried out using the laser knife method. The principle of this method consists of the following. A light beam is formed by a lens system, a mirror and slitted diaphragm into a fine beam and then guided into the cross section of the model to be investigated. A solution is introduced into the fluid flow having fluorescent properties such that the maximum fluorescent radiation lies in a longer wavelength region than the maximum spectral light intensity. The molecules of the fluorescent substance, when the pencil of light rays strike the flowing fluid, initiate light emission of a characteristic fluorescent wave length. Since the characteristic time for the process of light absorption, molecular excitation, and radiation (fluorescence) is short, usually 10 -~ to 10 -s sec, the resulting pictures portray the instantaneous distribution of the fluorescent substance in the complete stream. It should be pointed out that the presented kinogram shows the instantaneous distribution of the fluorescent substance in a section not a projection, as would be the case when using a dye solution. A schematic diagram of the experimental setup is presented in Fig. i. The AV 1 and AHVs 2 were placed in a rectangular-shaped vessel 3 filled with water. Water was utilized as the working fluid. Fluid was supplied to the AV from an upper supply tank 4 and ran off into a lower tank 5. Illustrated in Fig. 2 is the variant 1 orientation in the AV of the EMIKS type AHV disks, where the right valve is the input and the left is the output. Flow visualization was carried out at sections A--A and B--B. Visualization was conducted under stationary flow conditions with two different values for the flow rate: gl = 0.6