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A conical hot-film probe was used to measure instantaneous velocities in the ascending and descending aorta of anesthetized open-chest dogs. From these point measurements, the radial distributions of velocity were obtained over one cardiac cycle. In general, the hot-film measurements confirmed the observation that the velocity profiles tend to be flat with the highest rates of shear confined to the region of the wall. There were, however, significant variations in the detail from one dog to another. These variations in the shape of the profiles probably are a consequence of many geometrical factors, which include valve inlet geometry, configuration and orientation of the valve plane, and aortic curvature and branching in the descending aorta. KEY WORDShot-film probe aortic blood flow velocity profile cardiac output rates of shear pulsatile flow• At the current time most instrumentation for hemodynamic studies measures the instantaneous volume of time-averaged bulk flow and does not permit detailed investigation of pulsatile phenomena. Yet it is apparent that there are a number of important questions in the field of circulatory physiology which can be answered only by detailed in vivo measurements of pulsatile blood flow. One would like to know, for example, the magnitude of the local shearing stresses in the arterial system, for it is widely believed that when these stresses are sufficiently large the cellular elements in the blood are irreparably damaged. Endothelium lining the blood vessels may similarly be subjected to damage by these same stresses acting at the walls. The physiological significance of pulsatile motions on the blood vessel walls, particularly the aorta, is also of interest. This work was supported by the Heart Association of Southwestern New York, the Heart Association of Western New York, and the National Institute of Health Bio-Medical Fund.Parts of this work were presented at the 43rd Annual Meeting of the American Heart Association in Atlantic City on November 12, 1970. Received August 28, 1971. Accepted for publication June 20, 1972. These walls contain both active (muscle) and passive (connective) tissues which cause the vessel to change dimensions during the flow period and thus modulate the flow developed initially by the heart. One might also inquire about the flow phenomena which contribute to the opening and the closing of the heart valves or about the effect of branching in the vessels on the shape of the flow pulse. These questions and many more have been addressed in the past. However, since detailed flow measurements are unavailable, the answers necessarily are incomplete.To make in vivo measurements of instantaneous point velocities, a probe is needed which (1) is small compared to the size of the containing vessel, (2) possesses a reasonably high frequency response and (3) is strong. One probe having these characteristics is the hot-film probe used successfully for a number of years in engineering studies of more general fluid motions. Recent studies (1-7) show th...

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A distorted hydraulic model of Lake Ontario has been constructed and operated in a rotating laboratory.The model study includes the cffccts of the earth's rotation, gravity, and hydraulic through-flow. Boundary shear in the model was checked against theoretical predictions of scichc decay. Wind shear was adjusted to achieve appropriately scaled drift velocities in the model. Observed surface and subsurface circulation patterns are presented for a homogeneous and stratified lake model with and without a westerly wind.