Steady Laminar Fluid Flow Through Variable Constrictions in Vascular Tube

Steady laminar flow fields in the neighborhoods of two consecutive constrictions in a vascular tube were studied for approaching Reynolds number Re in the range of 5 to 200. The upstream stenosis was set at a dimensionless diameter constriction c₁ of 0.5 while the downstream stenoses were allowed to vary from c₂ = 0.2 to 0.6. The proximity of the constrictions was determined by the spacing ratio of S/D = 1, 2, 3, and ∞. When c₂ > c₁, a recirculation zone filled the valley between the two constrictions with little changes to the separation and reattachment points as Re was further increased. For c₂ < c₁ and when Re was increased, the recirculating eddy formed downstream of the first constriction tended to spread beyond the region of the second constriction. This resulted in negative wall vorticity peak occurring in the region of the second constriction for smaller S/D at high Re.