Turbulent flow through a natural human mitral valve

Turbulent characteristics of pulsatile fluid flow through a natural human mitral valve opening were measured with a pair of linearized, cylindrical hot-film anemometer probes oriented orthogonally to each other. A normal adult human mitral valve, excised along the annulus base during an autopsy, was carefully sutured into the valve section of a transparent plastic model chamber to preserve the geometry. The chamber was fabricated to reproduce the cross-sectional area of the human left ventricular cavity during diastole. A pneumatically powered pulsatile diaphragm pump drove the testing fluid, 36.7% (by volume) aqueous-glycerol solution, through the chamber at the flow rate of 51./min. Throughout the experiment, the pulse rate was kept at a constant 72 beats per min. The turbulent intensities and Reynolds stress immediately downstream from the mitral valve leaflet were evaluated during the end-diastolic and pre-systolic periods while the flow through the mitral valve was at its maximum rate. The analog signal was digitized and then processed to obtain phase averages of the variation of mean velocity, distributions of turbulent intensities, and Reynolds stresses. The phase average is conditioned on an amplitude threshold of the pressure drop across the valve during diastole; the periodic pressure drop served as the reference clock for the phase averaging process. Signal processing of the kind applied here provides meaningful data in pulsatile turbulent flows and appears to be new in experimental investigations of cardiovascular flows.