Abstract
Turbulence velocity has been measured in the canine ascending aorta using a hot-film anemometer. An experimental setup capable of producing a wide range of cardiac output as well as heart rate in the normal cardiac contractile state was used. Blood flow velocity was measured at various points across the ascending aorta approximately 1.5 to 2 times the diameter downstream from the aortic valve.
Turbulence spectrum (normalized energy density function E (k) ) was calculated from the blood flow velocity data by the fast Fourier transform technique. Characteristics of the turbulence spectrum were examined in connection with the mean Reynolds number and/or measuring positions.
Results :
1) In the higher wave number range, the values of the turbulence spectra are higher at larger mean Reynolds number. There is a wide range of wave numbers for which the spectrum slope is-5/3, when the mean Reynolds number is large. This suggests the existence of inertial subrange.
2) In the higher wave number range, the values of the turbulence spectra are higher at points closer to the centerline of the aorta, when the mean Reynolds number is relatively large.
3) The patterns of the turbulence spectra at various points outside the boundary layer on the aortic wall are similar. In the ascending aorta, the range of the effect of the wall on turbulence seems to be limited to its vicinity.
