SUMMARYThe dye-injection technique was used to study flow patterns in twelve glass models of the union of two streams to form a common stem as occurs in veins and, less often, in arteries. The angle of union and the sharpness of the apex of the union varied. Flow disturbances, though minor at low flow rates, were observed in the stem beyond the junction in all models at Reynolds numbers below 2000. The disturbances were attributed to instability in the wake of the junction and to boundary layer separation at the apex. The results indicate possible applicability to the human vascular system.

SUMMARYFlow patterns in twenty-one glass models of S bends were examined using the dye-injection technique. The glass models were of different configurations designed to simulate arterial tortuosities. In each model flow disturbances were observed in the stem distal to the S bend or in the distal portion of the S bend itself at Reynolds numbers below 2000. The disturbances were periodic in nature and mostly regular, but with considerable sensitivity to external disturbances. The sharpness of the flexures appeared to be important in determining the Reynolds number at which flow disturbances occurred. The significance of the flow disturbances is their seeming applicability to the human vascular system.