Radial variations in residence time distribution for pipe flows

Suspensions of low-diffusing particles in pipe flows exhibit a difference in age at different radial positions. Particles near the channel walls have higher residence times than the cross-sectional average. We quantify this effect using Monte Carlo simulations and show the existence of two different regimes: a “transitional” regime where delay compounds with channel length and a “far-field” regime where diffusion counterbalances advection. The results presented therein can be used to quantify residence time distributions near the walls of the tube. This effect is important to consider in experiments involving the kinetics of nanometer-scale particles using modern inline analytical tools. This work also provides a radially resolved extension of classical Taylor dispersion results.