Three-dimensional coarse large-eddy simulations of the flow above two-dimensional sinusoidal waves

Salvetti, Maria Vittoria; Damiani, Rick; Beux, F.

doi:10.1002/1097-0363(20010330)35:6<617::aid-fld104>3.0.co;2-m

Cited by 18 publications

(19 citation statements)

References 26 publications

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“…Most numerical simulations (RANS, large-eddy simulations, direct numerical simulations) and experiments in water have been performed in the transitional regime (Buckles et al 1984, Cherukat et al 1998, de Angelis et al 1997, Frederick & Hanratty 1988, Henn & Sykes 1999, Zilker & Hanratty 1979, for which the linear regime itself is not well understood, as discussed above. In the simpler turbulent regime, the qualitative aspects of the nonlinear hydrodynamical response have been elucidated from field observations, wind-tunnel experiments, and numerical simulations over both the sinusoidal bottom and isolated bumps (Buckles et al 1984, Finnigan et al 1990, Gong & Ibbetson 1989, Gong et al 1996, Salvetti et al 2001, Taylor et al 1987, Yue et al 2006, Zilker & Hanratty 1979. The linear asymptotic theory of Hunt et al (1988) still predicts the dominant features of the flow (Belcher & Hunt 1998).…”

Section: Beyond the Linear Responsementioning

confidence: 99%

Sand Ripples and Dunes

Charru

Andreotti

Claudin

2013

Annu. Rev. Fluid Mech.

248

305

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An erodible bed sheared by a fluid flow, gas or liquid, is generally unstable, and bed forms grow. This review discusses the following issues, in light of the recent literature: What are the relevant dynamical mechanisms controlling the emergence of bed forms? Do they form by linear instability or nonlinear processes such as pattern coarsening? What determines their timescales and length scales, so different in air and water? What are the similarities and differences between aeolian and subaqueous patterns? What is the influence of the mode of transport: bed load, saltation, or suspension? Can bed forms emerge under any hydrodynamical regime, laminar and turbulent? Guided by these questions, we propose a unified description of bed-form growth and saturation, emphasizing the hydrodynamical regime in the inner layer and the relaxation phenomena associated with particle transport. 469

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Section: Beyond the Linear Responsementioning

confidence: 99%

Sand Ripples and Dunes

Charru

Andreotti

Claudin

2013

Annu. Rev. Fluid Mech.

248

305

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“…While there are also examples of older numerical studies studying the flow structure in these environments [15,16], it is only recently that high resolution, eddy-resolving numerical studies have been performed [17,18], and flow structure generation mechanisms have been considered using numerical models [19][20][21][22]. In the context of the two-dimensional dunes that have tended to form the emphasis of previous experimental work [12,13,18,19,22], recent work has focused on the generation mechanisms describing the large-scale hairpin features in such flows, with a variety of mechanisms proposed:…”

Section: Introductionmentioning

confidence: 99%

Large eddy simulation of the velocity-intermittency structure for flow over a field of symmetric dunes

2016

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Owing to their frequent occurrence in the natural environment, there has been significant interest in refining our understanding of flow over dunes and other bedforms. Recent work in this area has focused, in particular, on their shear layer characteristics and the manner by which flow structures are generated. However, field-based studies, are reliant on single-, or multi-point measurements, rather than delimiting flow structures from the velocity gradient tensor as is possible in numerical work. Here, we extract pointwise time series from a well-resolved large-eddy simulation as a means to connect these two approaches. The at-a-point analysis technique is termed the velocityintermittency quadrant method and relates the fluctuating, longitudinal velocity, u ′ 1 (t), to its fluctuating pointwise Hölder regularity, α ′ 1 (t).Despite the difference in boundary conditions, our results agree very well with previous experiments that show the importance, in the region above the dunes, of a quadrant 3 (uflow configuration. Our higher density of sampling beneath the shear layer and close to the bedforms relative to past experimental work reveals a negative correlation between u ′ 1 (t) and α

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“…The main limitation of the up-to-date eddy-resolving studies of channel flow over arrays of regular large-scale fixed bedforms is the reduced length of the computational domain in the streamwise and spanwise directions. For example, most of the DNS [e.g., de Angelis et al, 1997;Cherukat et al, 1998] and LES [e.g., Salvetti et al, 2001] studies of flow-past sinusoidal dunes were conducted with periodic boundary conditions in the streamwise direction and in computational domains containing only a couple of bedforms and extending less than 3h in the spanwise direction. In the case of flow-past dunes and ripples of more realistic (asymmetric) shapes, most of the previous LES studies [e.g., Zedler and Street, 2001;Yue et al, 2005aYue et al, , 2005bYue et al, , 2006Stoesser et al, 2008;Grigoriadis et al, 2009] were conducted in a computational box containing only one dune in the streamwise direction and having a spanwise length of less than 2h.…”

Section: Introductionmentioning

confidence: 99%

Coherent structures in flow over two‐dimensional dunes

Chang

Constantinescu

2013

Water Resources Research

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[1] The instantaneous turbulent flow fields over a smooth bed and a bed containing largescale roughness elements are characterized by the presence of elongated low and high streamwise momentum regions or streaks. If the bed contains large-scale roughness elements (e.g., dunes), the size of the streaks increases and is of the order of the size of these elements and the flow depth. The present large eddy simulation (LES) study focuses on the case of developing flow within wide channels containing at the bottom a long array of spanwiseoriented sinusoidal 2-D dunes (2a/h ¼ 0.1, /h ¼ 1, is the wavelength, 2a is the dune height, and h is the mean flow depth) and an array of 2-D asymmetric dunes (2a/h ¼ 0.25, / h ¼ 3.75) of closer shape to the ones observed in natural streams. For the case of an incoming steady flow, the instantaneous flow fields, in the region where the flow transitions toward a fully developed turbulent flow regime, contain arrays of highly organized hairpin vortices, whose dimensions are larger than the dune height. The LES shows that for relatively shallow channels (e.g., channels with 2a/h ¼ 0.25), the large-scale hairpins and the streaks penetrate regularly up to the free surface, thus affecting mass transport and mixing over the whole water column. This paper explained the mechanism for the formation of these arrays of hairpin vortices and discussed the changes between a case with asymmetric dunes that are characterized by a large value of /2a (¼ 15) and a long upslope face and a case with symmetric dunes for which /2a ¼ 10, the upslope face is relatively short, and the rate of change of the bed curvature around the dune's crest is relatively small. The study discusses the main mechanisms through which large-scale hairpin form and how these mechanisms change between two dune geometries (sinusoidal versus asymmetric dunes). This study also shows that hairpin eddies play the primary role in the formation of the streaks over the region containing dunes and provides an estimation of the average dimensions of these streaks. The presence of resolved turbulence in the incoming flow reduces the streamwise distance needed for the streaks to develop over the region containing dunes, but does not qualitatively affect the transition process toward the fully developed flow regime nor the spacing of the streaks in the fully developed flow region.Citation: Chang, K. S., and G. Constantinescu (2013), Coherent structures in flow over two-dimensional dunes, Water Resour.

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Three-dimensional coarse large-eddy simulations of the flow above two-dimensional sinusoidal waves

Cited by 18 publications

References 26 publications

Sand Ripples and Dunes

Sand Ripples and Dunes

Large eddy simulation of the velocity-intermittency structure for flow over a field of symmetric dunes

Coherent structures in flow over two‐dimensional dunes

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