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Solute transport and mixing at channel-flow–porous media interfaces are strongly influenced by velocity and turbulence structures near porous media, and such coupled channel-flow–porous media systems are commonly observed in nature. However, the effects of pore-scale flows on solute transport in the coupled systems are currently unclear. In this study, we combine particle image velocimetry experiments and large eddy simulations to resolve the pore-scale flow characteristics over and within a porous bed. Then, we perform solute transport simulations by coupling the pore-scale flow fields with a particle-tracking model and show that the pore-scale flows inherent to porous media structure control solute transport. Pore-scale flow properties such as preferential downward–upward flows and vortices occurring near the channel-flow–porous media interface are shown to exert dominant control over interfacial mass exchange and solute transport. To clarify the effects of pore-scale flows on reach-scale transport, we conduct macroscale transport modeling with a spatially averaged stream-wise velocity profile. Because the profile-based model does not incorporate important pore-scale flow features, it significantly overestimates mass transfer into the porous bed, thereby exacerbating late-time tailings in breakthrough curves. Finally, a spatial Markov model, a type of upscaled stochastic transport model, is shown to effectively capture the pore-scale interfacial transport mechanisms via a velocity transition matrix. Our findings confirm that solute transport through channel-flow–porous media interfaces is controlled not only by interfacial turbulent-mixing profiles but also by detailed pore-scale flow structures. Article Highlights: We demonstrate the effects of pore-scale flows on solute transport in coupled turbulent channel-flow–porous media systems Pore structure near the interface exerts dominant control over interfacial mass exchange and solute transport Spatial Markov model effectively upscales the effects of pore-scale flows on solute transport. [ABSTRACT FROM AUTHOR]

Large-eddy simulations are used to investigate the effects of coastal topography and atmospheric stratification on the coastal marine atmospheric surface layer at the Field Research Facility in Duck, North Carolina, USA. Field measurements obtained from the CASPER-EAST intensive field campaign in autumn 2015 are used to determine the inlet and lower boundary conditions. The simulations are performed using the in-house Virtual Flow Simulator code, with the simulated mean streamwise velocity component, mean temperature, Reynolds shear stress, and turbulent heat flux, shown to be in good agreement with measurements. In the coastal area, the complex coastal topography leads to an enhancement of the Reynolds shear stress for both onshore and offshore flows, while the effect of atmospheric stratification on the momentum transfer is less significant than the topography. In contrast to the momentum flux, the heat flux is influenced by both the coastal topography and stratification. For onshore flow and stable stratification, the heat flux is significantly increased near the sand dune due to the enhanced turbulence and vertical temperature gradient. For onshore flow and unstable stratification, the strong turbulent mixing tends to enhance the heat flux, but is suppressed by the reduced vertical temperature gradient, such that the magnitude of the turbulent heat flux remains almost unchanged in comparison with the upstream flow. For offshore flow in both stable and unstable stratification, the heat flux is enhanced due to the flow separation at the sand dune. [ABSTRACT FROM AUTHOR]