Abstract
The steady flow conditions in a rigid model of the aortic-renal junction were studied in the relation to atherogenesis in humans. The streamline flow patterns were visualized by a slow injection of dye at different locations over the cross section of the tube entrance and through small holes machined along the tube walls. The particle residence time was estimated by measuring the washout time of a bolus of dye injected at the separation point. Streamlines deviate, in general, towards the branch orifice. Streamlines located near the outer (dorsal) wall of the trunk drifted towards the inner wall after passing the branching region, but they sometimes change direction and entered the branch. Streamlines near the ventral wall of the trunk entered the side branch directly. in the side branch the streamlines moved towards the inner wall of the branch and this results in a secondary flow with helical motion. Two boundary layer separation zones were observed to occur in the model, one was found at the outer wall of the trunk and the other at the outer corner of the branch. Fluid within separation zones exhibited helical (disturbed motion) with prolonged residence time. The residence time was found to decrease as the Reynolds number increase. The size of the separation zone in the trunk increases as the outflow into the side branch increased, while the size of the separation zone in the branch increased as the outflow into it increased for the range of flow ratio of 0.0 to 0.5. This size however was found to be smaller at a flow ratio of 0.65. A long residence time would mean that atherogenic particles trapped within the separation zones will have a greater probability of being deposited there.