Flow in Glass Models of Arterial Bifurcations and Berry Aneurysms at Low Reynolds Numbers

Abstract

Using the dye injection technique, flow at low Reynolds numbers was studied in glass models which simulated arterial bifurcations of varying angles and had varying bluntness of the apex or crotch. Forks bearing small saccular evaginations simulating berry aneurysms were investigated similarly. At quite low Reynolds numbers in all the models small wave motion was observed at the forks. At higher Reynolds numbers and below the critical values for turbulence, larger vortices akin to a K'arman vortex street were shed from most of the forks. The disturbances were attributed to boundary layer separation and a jet-edge effect.

Flow in Glass Models Simulating Vascular Junctions Under Steady Flow Conditions

“…The minor variations in dye intensity or rippling have been observed at low Reynolds number beyond a stenosis (Johansen, 1929), in glass models simulating arterial bifurcations (Stehbens, 1975) and in a thin film of liquid flowing down a vertical plate (Binnie, 1957). These ripples precede coarser periodic flow disturbances either at higher flow velocities or as the result of external disturbances.…”

“…This would have had the effect of an ampulla at the commencement of the stem. Just as it has been shown that the radius of curvature or bluntness of the apex of a bifurcation influences the onset of flow disturbances (Stehbens, 1975), so in reverse flow through the models, bluntness of the apex and the cross-sectional area at the confluence of the two tributaries affect flow at that site. Minor variations in architecture of the models at the junction may therefore influence flow and probably account for some inconsistencies in Table 1.…”

“…The glass models used were manufactured from glass tubing by an experienced glass blower, and were the same as or similar to those used in previous flow studies of simulated arterial bifurcations (Stehbens, 1975) but with flow in the reverse direction. All models consisted of a 60 cm glass stem with an internal diameter of 0 95 cm.…”

“…The predilection of arterial forks for atherosclerosis and the belief that haemodynamics plays an important role in atherogenesis have resulted in numerous investigations of flow in arterial and model bifurcations (Stehbens, 1959(Stehbens, , 1975Roach, Scott & Ferguson, 1972;Karino, Motomiya & Goldsmith, 1983;Leipsch, Moravec & Zimmer, 1983). Analysis of flow patterns at branching sites presents an extremely difficult hydrodynamic problem and the relationship of the flow disturbances generated at bifurcations to intimal proliferation and atherosclerosis is controversial (Stehbens, 1960a(Stehbens, , 1979.…”

Flow Instability Detected by High-Resolution Computational Fluid Dynamics in Fifty-Six Middle Cerebral Artery Aneurysms

“…in vivo, velocity fluctuations have been found in some patients intra-operatively prior to aneurysm clipping. However, their association with rupture has not been determined [9][10][11][12]. Similarly, in vitro particle image velocimetry measurements [13] and flow visualization in experimental glass models have also noted unstable flow within vasculature models [12,14,15].…”