FLOW PATTERNS IN DOG AORTIC-ARCH UNDER A STEADY FLOW CONDITION SIMULATING MID-SYSTOLE

To elucidate the possible connection between blood flow and localized pathogenesis and tile development of atherosclerosis in humans, we stu died the flow patterns and the distribution of fluid axial velocity an d wall shear stress in the aortic arch in detail, This was done by mea ns of flow visualization and highspeed cinemicrographic techniques, us ing transparent aortic tries prepared from the dog, Under a steady flo w condition at inflow Reynolds numbers of 700-1600, which simulated ph ysiologic conditions at early- to mid-systole, slow, spiral secondary, and recirculation flows formed along the left anterior wall of the ao rtic arch and at the entrance of each side branch adjacent to the vess el wail opposite the flow divider, respectively. The flow in the aorti c arch consisted of three major components, namely, an undisturbed par allel now located close to the common median plane of the arched aorta and its side branches, a clockwise rotational now formed along the le ft ventral wall, and the main flow to the side branches, located along the right dorsal wall of the ascending aorta, Thus, looking down the aorta from its origin, the flow in the aortic arch appeared as a singl e helical flow revolving in a clockwise direction, Regions of low wall shear stress were located along the leading edge of each side branch opposite the flow divider where slow recirculation flows formed, and a long the left ventral wall where slow spiral secondary flows formed. I f we assume that the flow patterns in the human aortic arch well resem ble those observed in the dog, then it is likely that atherosclerotic lesions develop preferentially at these sites of low wall shear stress in the same manner as in human coronary and cerebral arteries.