Large eddy simulation of turbulent flow over and through a rough permeable bed

Lian, Yuan; Dallmann, J.; Sonin, Benjamin H.; Roche, Kevin; Liu, W.K.; Packman, Aaron I.; Wagner, Gregory J.

doi:10.1016/j.compfluid.2018.12.015

Cited by 18 publications

(15 citation statements)

References 38 publications

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“…mountain rivers processes, hyporheic processes or heat transfers). These results could also be useful to test and validate large-eddy-simulation models (Fang et al 2018;Lian et al 2019) or models based on double-averaged or Reynolds averaged momentum equations (as in Maurin et al (2018) for instance).…”

Section: Discussionmentioning

confidence: 99%

Scanning PIV of turbulent flows over and through rough porous beds using refractive index matching

Rousseau

Ancey

2020

Exp Fluids

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This paper presents image velocimetry measurements on turbulent flows adjacent to a permeable bed made of randomly packed glass particles. For measuring flow velocities inside the bed, the refractive index of the glass particles was matched with that of the fluid. By continuously scanning in the transverse direction, we measured the streamwise and vertical velocity components within a three-dimensional domain (3D2C-PIV), including first-and second-order turbulent statistics. We established how the scanning travel speed is associated with the laser sheet thickness and the space-time velocity fluctuations for collecting reliable measurements. The methodology was applied to free-surface flows over a sloping bed under low relative submergence and supercritical conditions. Space-and time-averaged profiles were obtained in a representative elementary volume as defined by the double-averaging procedure (Nikora et al. in J Hydraulic Eng.127(2):123-133, 2001). A turbulent boundary layer over the rough bed was observed when experiments were run at intermediate Reynolds numbers Re = O(1000) . Apart from measuring subsurface velocities, this method shed light on the part played by the rough bed in the overall flow dynamics: the roughness layer was a buffer region within which porosity varied sharply and turbulent stress was rapidly dampened.

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Section: Discussionmentioning

confidence: 99%

Scanning PIV of turbulent flows over and through rough porous beds using refractive index matching

Rousseau

Ancey

2020

Exp Fluids

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“…Given a sphere diameter

D = 38

mm and a uniform spacing between spheres of

d_{g} = 2

mm, the cell length

L = D + d_{g} = 40

mm and normalized vertical distance

z^{*} = \frac{z}{L}

are used to spatially define the domain, which has dimensions of 15

L \times

L \times

L

x

y

, and

z

directions, respectively. This domain was found to be large enough to allow for the formation of the largest structures, diminishing the impact of spanwise locking on simulation results (Lian et al., 2019). The gap

d_{g}

was chosen to be as small as possible without requiring meshing near a singular contact point.…”

Section: Methodsmentioning

confidence: 99%

“…𝐴𝐴 𝐴𝐴 , and 𝐴𝐴 𝐴𝐴 directions, respectively. This domain was found to be large enough to allow for the formation of the largest structures, diminishing the impact of spanwise locking on simulation results (Lian et al, 2019). The gap 𝐴𝐴 𝐴𝐴𝑔𝑔 was chosen to be as small as possible without requiring meshing near a singular contact point.…”

Section: Numerical Modelmentioning

confidence: 99%

Double Averaging Analysis Applied to a Large Eddy Simulation of Coupled Turbulent Overlying and Porewater Flow

Lian

Dallmann

Sonin

et al. 2021

Water Resources Research

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“…The constant C w = 0.325 and V c is the volume of the grid cell. While the WALE model can be overdissipative in strong vortical flows (Bricteux, Duponcheel & Winckelmans 2009), it has been found to perform better than the dynamic Smagorinsky model for simulating flow separation (Arya & De 2019) and flow over rough beds (Lian et al 2019). For this study, the main turbulent generation mechanism is eddies shed from the roughness elements and no strong shear layers formed; therefore, the WALE model is appropriate.…”

Section: Large-eddy Simulation Modelmentioning

confidence: 97%

Boundary layer dynamics and bottom friction in combined wave–current flows over large roughness elements

Rosman

Hench

2021

J. Fluid Mech.

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In the coastal ocean, interactions of waves and currents with large roughness elements, similar in size to wave orbital excursions, generate drag and dissipate energy. These boundary layer dynamics differ significantly from well-studied small-scale roughness. To address this problem, we derived spatially and phase-averaged momentum equations for combined wave–current flows over rough bottoms, including the canopy layer containing obstacles. These equations were decomposed into steady and oscillatory parts to investigate the effects of waves on currents, and currents on waves. We applied this framework to analyse large-eddy simulations of combined oscillatory and steady flows over hemisphere arrays (diameter $D$ ), in which current ( $U_c$ ), wave velocity ( $U_w$ ) and period ( $T$ ) were varied. In the steady momentum budget, waves increase drag on the current, and this is balanced by the total stress at the canopy top. Dispersive stresses from oscillatory flow around obstacles are increasingly important as $U_w/U_c$ increases. In the oscillatory momentum budget, acceleration in the canopy is balanced by pressure gradient, added-mass and form drag forces; stress gradients are small compared to other terms. Form drag is increasingly important as the Keulegan–Carpenter number $KC=U_wT/D$ and $U_c/U_w$ increase. Decomposing the drag term illustrates that a quadratic relationship predicts the observed dependences of steady and oscillatory drag on $U_c/U_w$ and $KC$ . For large roughness elements, bottom friction is well represented by a friction factor ( $f_w$ ) defined using combined wave and current velocities in the canopy layer, which is proportional to drag coefficient and frontal area per unit plan area, and increases with $KC$ and $U_c/U_w$ .

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Large eddy simulation of turbulent flow over and through a rough permeable bed

Cited by 18 publications

References 38 publications

Scanning PIV of turbulent flows over and through rough porous beds using refractive index matching

Scanning PIV of turbulent flows over and through rough porous beds using refractive index matching

Double Averaging Analysis Applied to a Large Eddy Simulation of Coupled Turbulent Overlying and Porewater Flow

Boundary layer dynamics and bottom friction in combined wave–current flows over large roughness elements

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