Fig. 7

Actual PAS cross-sections measured in vivo are nearly optimal. a Hydraulic resistance \(\mathcal {R}\) as a function of \((\alpha - \beta )/K\) in which \(\alpha \) varies and the values of the area ratio K and eccentricities \(\epsilon _x\) and \(\epsilon _y\) are fixed corresponding to the fitted values obtained in Table 1. Values corresponding to plots B-D are indicated. b–d Velocity profiles for the optimal value of \(\alpha \) (left column), which correspond to the minimum value of \(\mathcal {R}\) on each curve in A, and velocity profiles for the exact fit provided in Table 1 (right column) and plotted in Fig. 1b–d, respectively. The shape of the PAS measured in vivo is nearly optimal