Experimental and numerical study of flow structure in a model of distal anastomosis of femoral artery

The physical and numerical simulation of steady blood flow was carried out focusing on the distal end-to-side anastomosis of a graft to the femoral artery. The angle between the graft and the artery was 60°. Two Reynolds numbers were considered that corresponded to the physiological range when estimated using average (Re = 240) and maximum (Re = 1640) blood flow through the human femoral artery over a single cardiac cycle. The experiment included flow visualization and measurements of instantaneous vector fields of velocity using an optical SIV (Smoke Image Velocimetry) technique. Direct numerical simulation (DNS) was employed for numerical study. The distribution of blood flows through the branches of the main artery was 80% in the antegrade and 20% in the retrograde direction. Principal patterns in the distribution of velocity and its root-mean-square fluctuations in both branches of the main artery were revealed. The formation of flow separation regions in the branching region was observed. Additionally, secondary flows (Prandtl's vortices of the second kind) were revealed. At Re = 240, the flow in the branching region was still laminar, while at Re = 1640 the signs of transition to turbulence localized within separation regions were documented. Distributions of the streamwise and circumferential components of skin friction vector were estimated. In some regions of flow, these components were shown to be comparable in size. The location of regions was revealed in which the magnitude of friction in the considered flow regimes was lower than the one in an unimpaired artery (developed laminar flow in a circular pipe) at appropriate Reynolds numbers.