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Instantaneous blood velocity measurements employing a constant temperature hot film anemometer were obtained in the region distal to externally enforced, subtotal vascular stenoses in the descending thoracic aortas of anesthetized dogs. Our objectives were to determine alterations in velocity waveforms and energy spectra as the degree of stenosis was increased. We paid particular attention to distinguishing features of the flow which were characteristic of turbulence. Our results indicate that, for the vessels studied, disturbances in the velocity waveforms occur for very minor localized constrictions. The energy spectra follow certain similarity parameters within a restricted region of the distal velocity field. For severe stenoses relatively high levels of energy exist in frequency ranges which previously have been found to produce poststenotic dilation. The measurements suggest that velocity waveforms and energy spectra provide a very early clue to the existence of localized occlusive vascular disease in larger vessels and that, within a limited region distal to a stenosis, the degree of constriction may be estimated by similarity analysis of the energy spectra.

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The flow field of a sonic jet exhausting counter to a supersonic airstream has been investigated theoretically and experimentally. An inviscid analysis shows the shock layer thickness and the position of the outer and inner shocks to be a function of free stream Mach number, jet reservior pressure, free stream Pitot pressure, and orifice size. The predicted inner shock position agrees with previous data in the continuum. The experiments were conducted in a Mach 3 low-density wind tunnel at free stream Re/l == 2.9 to 31.5 per cm and p0i/p′0∞ 10 to 104. The experimental results in the transition regime show the orifice to outer shock distance is greater than the predicted inviscid value.