Anatomy and propagation dynamics of continuous-flux release bottom gravity currents through emergent aquatic vegetation

Testik, Firat Yener; Yilmaz, Nazli

doi:10.1063/1.4919783

Cited by 21 publications

(8 citation statements)

References 55 publications

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“…Testik & Ungarish (2016) conducted a theoretical analysis on both LR and continuous-flow GCs in a rectangular channel in the presence of artificial vegetation (cylindrical rods), comparing the results with previous experimental studies by Hatcher et al (2000), Tanino, Nepf & Kulis (2005) and Testik & Yilmaz (2015). Testik & Ungarish (2016) solved a more general model, in which the drag force is proportional to |u| λ , with u being the horizontal velocity and λ a constant positive value.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on radial gravity currents flowing in a vegetated channel

et al. 2022

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We present an experimental study of gravity currents in a cylindrical geometry, in the presence of vegetation. Forty tests were performed with a brine advancing in a fresh water ambient fluid, in lock release, and with a constant and time-varying flow rate. The tank is a circular sector of angle $30^\circ$ with radius equal to 180 cm. Two different densities of the vegetation were simulated by vertical plastic rods with diameter $D=1.6\ \textrm{cm}$ . We marked the height of the current as a function of radius and time and the position of the front as a function of time. The results indicate a self-similar structure, with lateral profiles that after an initial adjustment collapse to a single curve in scaled variables. The propagation of the front is well described by a power law function of time. The existence of self-similarity on an experimental basis corroborates a simple theoretical model with the following assumptions: (i) the dominant balance is between buoyancy and drag, parameterized by a power law of the current velocity $\sim |u|^{\lambda-1}u$ ; (ii) the current advances in shallow-water conditions; and (iii) ambient-fluid dynamics is negligible. In order to evaluate the value of ${\lambda}$ (the only tuning parameter of the theoretical model), we performed two additional series of measurements. We found that $\lambda$ increased from 1 to 2 while the Reynolds number increased from 100 to approximately $6\times10^3$ , and the drag coefficient and the transition from $\lambda=1$ to $\lambda=2$ are quantitatively affected by D, but the structure of the model is not.

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Section: Introductionmentioning

confidence: 99%

Experimental study on radial gravity currents flowing in a vegetated channel

et al. 2022

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“…As a result, the influence of these interactions on the sediment transport and deposition of the current is poorly understood at present. Recently, Testik & Yilmaz () have studied the propagation of continuous‐flux release gravity currents through emergent vegetation but experiments were conducted with non‐Newtonian mud gravity currents. To the knowledge of the present authors, the novelty of the present study is the fact that it has studied the effect of emergent vegetation on a gravity current driven by the presence of suspended particles, and not generated by a saline dissolution.…”

Section: Introductionmentioning

confidence: 99%

Sediment deposition from turbidity currents in simulated aquatic vegetation canopies

et al. 2017

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A laboratory flume experiment was carried out in which the hydrodynamic and sedimentary behaviour of a turbidity current was measured as it passed through an array of vertical rigid cylinders. The cylinders were intended primarily to simulate aquatic vegetation canopies, but could equally be taken to represent other arrays of obstacles, for example forests or offshore wind turbines. The turbidity currents were generated by mixing naturally sourced, poly‐disperse sediment into a reservoir of water at concentrations from 1·0 to 10·0 g l−1, which was then released into the experimental section of the flume by removing a lock gate. For each initial sediment concentration, runs with obstacle arrays with solid plant fractions of 1·0% and 2·5%, and control cases with no obstacles, were carried out. The progress of the current along the flume was characterized by the array drag term, CDaxc (where CD is the array drag coefficient, at the frontal area of cylinders per unit volume, and xc is the position of the leading edge of the current along the flume). The downward depositional flux of sediment out of the current as it proceeded was measured at 13 traps along the flume. Analysis of these deposits divided them into fine (2·2 to 6·2 μm) and coarse (6·2 to 104 μm) fractions. At the beginning of their development, the gravity currents proceeded in an inertia‐dominated regime until CDaxc = 5. For CDaxc > 5, the current transitioned into a drag‐dominated regime. For both fine and coarse sediment fractions, the rate of sediment deposition tended to decrease gradually with distance from the source in the inertial regime, remained approximately constant at the early drag‐dominated regime, and then rose and peaked at the end of the drag‐dominated stage. This implies that, when passing through arrays of obstacles, the turbidity currents were able to retain sufficient sediment in suspension to maintain their flow until they became significantly influenced by the drag exerted by the obstacles.

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“…In addition, the sediment transport and deposition rates from turbidity currents in these canopies are investigated and compared. This is an advance over previous studies of interactions between turbidity currents and canopies of obstacles, which have considered only continuous-release turbidity currents flowing through idealized emergent vegetation (Soler et al, 2017) and non-Newtonian mud flows (Testik and Yilmaz (2015).…”

Section: Introductionmentioning

confidence: 99%

Particle size segregation of turbidity current deposits in vegetated canopies

Soler

Colomer

Folkard

et al. 2020

Science of The Total Environment

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Interactions between ecology, hydrodynamics and sediments play central roles in the evolution of coastal and freshwater ecosystems. We set out to characterise interactions of a specific hydrodynamic phenomenon -turbidity currents -with vegetation and sediment dynamics. We measured hydrodynamics and sediment deposition rates when turbidity currents flowed into plant canopies in a lockexchange flume experiment, using simulated vegetation and three real plant species, and varying the turbidity current's initial sediment concentration in the range 1.0-6.0 gL -1 . The natural sediment used had an essentially bimodal size distribution, with coarse (6.2-104 μm) and fine (2.2-6.2 μm) fractions. In all cases, on entering the vegetation canopy, the turbidity current was initially inertially-dominated, but subsequently became drag-dominated. In the inertial regime, there was no size segregation in the deposited material. In the drag-dominated regime, the deposited material became increasingly dominated by fine sediment, at a rate dependent on the vegetation type. The transition between these two regimes occurred at a distance equivalent to 5.1 to 7.6 times the total water depth downstream of the lock gate. The size segregation of deposited sediment is posited to have important consequences for substrate evolution, which in turn may affect vegetation growth. Thus, our findings point to a non-linear feedback mechanism between the spatial heterogeneity of vegetation canopies and that of the substrate they help to engineer.

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Anatomy and propagation dynamics of continuous-flux release bottom gravity currents through emergent aquatic vegetation

Cited by 21 publications

References 55 publications

Experimental study on radial gravity currents flowing in a vegetated channel

Experimental study on radial gravity currents flowing in a vegetated channel

Sediment deposition from turbidity currents in simulated aquatic vegetation canopies

Particle size segregation of turbidity current deposits in vegetated canopies

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