A method for analyzing the turbulence phenomena in the aorta is presented. The blood velocity measured with a hot-film anemometer in the canine ascending aorta is referred in the discussion. All the experimental data were recorded on magnetic tape and processed on a digital computer after analog-to-digital conversion for the analysis. The turbulence velocity is defined as the difference between a sample velocity recording and the ensemble average of sample recordings. To discriminate the fluid dynamical fluctuations from physiological deviations, we used a threshold to exclude recordings with extraordinary amplitude and waveform due to the arrhythmia of the heart from the ensemble of the sample velocity recordings. Small deviations of the recordings due to respiratory changes were corrected with a coefficient which equates the time integral of each individual velocity recording to that of the ensemble average velocity. The mean turbulence intensity was calculated as the square root of the time mean of the ensemble average square of turbulent velocity during deceleration phase of the ensemble average velocity. The mean turbulence intensity defined above is shown to be related closely to the maximum of ensemble average velocity in each dog.
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