Figure 3.

Normalized stretching coefficient $\mu =2\lambda /3p$ as function of the Péclet number for $pL={10}^1$, ${10}^2$ and ${10}^3$ (bottom to top). In all cases, we set $l=1/p$, which corresponds to $L/l=pL$ and $\Delta =1/3$. The dashed lines represent the solution of the asymptotic Equation (31). The straight lines indicate the power-law dependencies $\mu \sim P{e}^{4/3}$ for $N={10}^3$ and $\mu \sim Pe$ for $N=10$ (cf. Equations (32) and (33), respectively).