Flow in glass models simulating vascular junctions under steady flow conditions.

The 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.