Motivated by the physiological phenomena of collapse and flow limitation for a serial pulmonary artery stenosis, we investigated the three-dimensional influence of spatial configuration on the wall motion and hemodynamic. Our numerical study focused on the effect of two geometrical parameters: the relative distance and the angular orientation between the two stenoses. The collapse of a compliant arterial stenosis may cause flow choking, which would limit the flow reserve to major vital vascular beds such as the lungs, potentially leading to a lethal ventilation-perfusion mismatch. Flow through a stenotic vessel is known to produce flow separation downstream of the throat. The eccentricity of a stenosis leads to asymmetric flow where the high velocity jets impinge on the sidewall, thereby inducing significant dissipation. The additional viscous dissipation causes a higher pressure drop for a flow through a stenotic vessel, than in a straight compliant vessel. It is likely that some particular morphology would have a higher vulnerability to the fluid induced instability of buckling (divergence), under physiological pulsatile flow. It was found that fluid pressure distribution have substantial implication for the downstream wall motion, under conditions of strong coupling between nonlinear vessel geometries, and their corresponding asymmetric flow. The three-dimensional fluid structure interaction problem is solved numerically by a finite element method based on the Arbitrary Lagrangian Eulerian formulation, a natural approach to deal with the moving interface between the flow and vessel. The findings of this investigation reveal that the closeness between stenoses is a substantial indication of wall collapse at the downstream end. Moreover, the results suggest a close link between the initial angular orientation of the distal stenosis (i.e. the constriction direction) and the subsequent wall motion at the downstream end. For cases showing evidence of preferential direction of wall motion, it was found that the constricted side underwent greater cumulative displacement than the straight side, suggestive of significant wall collapse.

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