Corrsin S.

Finnigan J. J.

Heidi M. Nepf

Hill R. J.

Kobashi D.

Kundu P. K.

Lienhard J. H.

Lightbody A. F.

Masuoka T.

Schwarzenbach R. P.

Shavit U.

Takatsu Y.

Tanino Y.

Yukie Tanino

Physics of Fluids

This material is based on work supported by the National Science Foundation under Grant No. EAR0309188. Any opinions, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. We thank the three anonymous reviewers for their comments.Peer reviewe

Tanino, Yukie

Nepf, Heidi M.

Aberdeen University Research

English

Laboratory investigation of lateral dispersion within dense arrays of randomly distributed cylinders at transitional Reynolds number

Relative (effective) lateral dispersion of a passive solute was examined at transitional Reynolds numbers within a two-dimensional array of randomly distributed circular cylinders of uniform diameter d. The present work focuses on dense arrays, for which previously developed theory [ Y. Tanino and H. M. Nepf, J. Fluid Mech. 600, 339 (2008) ] implies that the asymptotic (long-time/long-distance) dispersion coefficient, when normalized by the mean interstitial fluid velocity, 〈math〉, and d, will only exhibit a weak dependence on Reynolds number, Red ≡ 〈math〉d/ν, where ν is the kinematic viscosity. However, the advective distance required to reach asymptotic dispersion is expected to be controlled by pore-scale mixing, which is strongly Red-dependent prior to the onset of full turbulence. Laser-induced fluorescence was used to measure the time-averaged lateral concentration profiles of solute released continuously from a point source in arrays of solid volume fraction ϕ = 0.20 and 0.35 at Red = 48–120. Results are compared to previous measurements at higher Red. Lateral dispersion reaches the same rate as asymptotic dispersion in fully turbulent flow at x ≈ 154d at (ϕ,Red) = (0.20,110–120) and at x ≈ 87d at (ϕ,Red) = (0.35,300–390). In contrast, dispersion does not reach the fully turbulent flow limit at Red<100 within the range of x considered. Also, concentration profiles deviate further from a Gaussian distribution at ϕ = 0.35 than at 0.20 for similar Red and xϕ/d. From these observations, it can be inferred that the pre-asymptotic regime extends farther downstream, in terms of the number of cylinders spanned, at lower Red and at larger ϕ.National Science Foundation (U.S.) (Grant No. EAR0309188

Laboratory investigation of lateral dispersion within dense arrays of randomly distributed cylinders at transitional Reynolds number

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