Flow in axisymmetrical glass model aneurysms

Experiments have been performed on the flow of water with a dye tracer in rigid glass models of axisymmetrical spherical aneurysms. Streamlines have been visualized, pressure drops over the surface of the bulbs have been measured, and a critical Reynolds number for the onset of turbulence in the aneurysms has been determined. Boundary layer separation and recirculating flow with closed streamlines was observed in all models for flow rates below those necessary for turbulence. Pressures on the aneurysm walls for both laminar and turbulent flow were found to be of the same order of magnitude as those immediately upstream and downstream with no large pressure differences over the bulb surfaces. An inviscid mathematical model of the flow field was developed and shown to give good agreement with experiment for high Reynolds number laminar flow. The use of a suitably defined critical Reynolds number as an aid in the decision to operate on fusiform aneurysms is noted, as well as the limitations imposed on the experimental and theoretical results by the neglect of flow periodicity and nonhomogeneity.