Flow structure inside and around a rectangular array of rigid emerged cylinders located at the sidewall of an open channel

Köken, Mete; Constantinescu, George

doi:10.1017/jfm.2020.900

Cited by 21 publications

(25 citation statements)

References 71 publications

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“…see Kirkil & Constantinescu 2009, 2015; Chang et al. 2011, 2013; Chang, Constantinescu & Tsai 2017, 2020; Zeng & Constantinescu 2017; Koken & Constantinescu 2020). These studies have shown that for steady incoming flow conditions, DES can accurately predict the wake structure and dynamics of the shed billow vortices, the dynamics of the main horseshoe vortices and their interactions with the vortex tubes shed in the separated shear layers.…”

Section: Numerical Model Boundary Conditions and Test Casesmentioning

confidence: 99%

Oscillatory flow around a vertical circular cylinder placed in an open channel: coherent structures, sediment entrainment potential and drag forces

Chang

2023

J. Fluid Mech.

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Flow and turbulent structures generated by the interaction of forced incoming oscillatory flow with a circular, vertical cylinder placed in an open channel with a horizontal bed are investigated using eddy-resolving simulations. Validation simulations performed with a Keulegan–Carpenter (KC) number of 20 and multiple-mode forcing corresponding to the laboratory experiment of Sumer et al. (J. Fluid Mech., vol. 332, 1997, pp. 41–70) show that detached eddy simulation (DES) predicts more accurately the amplification of the bed shear stress beneath the horseshoe vortex system (upstream side of the cylinder) and the maximum magnitude of the bed shear stress at the downstream (wake) side of the cylinder compared with unsteady Reynolds-averaged Navier–Stokes simulations. High-Reynolds-number DES simulations are then conducted with 1.5 ≤ KC ≤ 30.8 and one-mode sinusoidal forcing of the streamwise velocity in the approaching flow to investigate the changes in the wake vortex-flow regimes, the coherence of the horseshoe vortices and the generation of other near-bed coherent structures in the wake during the oscillatory cycle. The flow is periodic, no horseshoe vortices form and no vortices are shed in the wake for KC = 1.5. By contrast, for KC ≥ 8 horseshoe vortices are present over part of the oscillatory cycle and up to three wake vortices are shed over each half-cycle as KC is increased to 30.8. For an intermediate range of KC numbers, one (KC = 15.4) or two (KC = 8) of the vortices forming at the back of the cylinder during each half-cycle are washed around it when the flow reverses. The main horseshoe vortex and other horizontal near-bed vortices have a large capacity to amplify the bed shear stresses when the incoming velocity magnitude is significantly less than its peak value. Assuming the depth-averaged velocity in the incoming (undisturbed) oscillatory flow is the same in simulations conducted with different KC numbers, the peak values of the sediment entrainment potential measured by the mean (cycle-averaged) volumetric flux of sediment entrained from the bed over one oscillatory cycle occur for 8 ≤ KC ≤ 15.4. For all KC numbers, the in-line force variation over the oscillatory cycle is fairly well approximated by the Morison equation. For KC = 1.5, the in-line force is only due to inertia effects. For KC = 30.8, the maximum and minimum values of the phase-averaged in-line force are approximatively in phase with those of the incoming flow velocity. For KC ≥ 15, the phase-averaged in-line force coefficients vary between 0.8 and 1.1 during most of the oscillatory cycle (e.g. when the incoming flow velocity is not close to zero). This is different from cases with KC ≤ 8 where the in-line force coefficient is equal to zero twice during the oscillatory cycle as the in-line force becomes equal to zero for non-zero values of the incoming velocity. The largest cycle-to-cycle variations of the in-line force coefficient and in-line force are observed around KC = 8. For KC = 8 and 15.4, the cylinder is subject to relatively large phase-averaged spanwise drag forces that are comparable to the peak phase-averaged streamwise drag forces. As KC is increased to 30.8, the phase-averaged spanwise drag force becomes zero over the whole oscillatory cycle but the cylinder is still subject to large instantaneous spanwise forces over part of the oscillatory cycle.

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Section: Numerical Model Boundary Conditions and Test Casesmentioning

confidence: 99%

Oscillatory flow around a vertical circular cylinder placed in an open channel: coherent structures, sediment entrainment potential and drag forces

Chang

2023

J. Fluid Mech.

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“…see White & Nepf 2007; Zong & Nepf 2011, 2012; Chen et al. 2012; Chang, Constantinescu & Tsai 2017; Koken & Constantinescu 2020). These studies considered either a circular or rectangular patch positioned at the centre of a straight channel, or a long rectangular patch placed at one of the channel's banks.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the development of the vertical shear layer is constrained by the free surface, especially for low submergence cases, while the development of the horizontal shear layer vortices is constrained by bed friction effects at large distances from the origin of the shear layer (Finnigan 2000; Sukhodolova & Sukhodolov 2012 a ; Cheng & Constantinescu 2020). Although the structure of the flow inside the horizontal shear layer was studied experimentally (White & Nepf 2007) and numerically (Koken & Constantinescu 2020) for emerged rectangular arrays, no such information is available for submerged arrays.…”

Section: Introductionmentioning

confidence: 99%

Influence of submergence ratio on flow and drag forces generated by a long rectangular array of rigid cylinders at the sidewall of an open channel

Köken

2023

J. Fluid Mech.

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This paper discusses how the submergence ratio, defined as the ratio between the flow depth, D, and the height, h, of the solid rigid cylinders forming the array affects flow and turbulence structure inside and around a rectangular array of cylinders placed adjacent to one of the channel sidewalls. As the array becomes submerged, a vertical shear layer develops in between the top face of the array and the free surface, which strongly increases flow three-dimensionality and modifies how the momentum exchange between the array and the surrounding open water regions occurs with respect to the case of an emerged array where only a horizontal shear layer forms as part of the incoming flow approaching the array is deflected laterally. Eddy-resolving simulations are conducted for several values of the solid volume fraction, ϕ, and of the submergence ratio, 1.0 ≤ D/h ≤ 4.0. Similar to the limiting case of an emerged array (D/h = 1.0), the width- and depth-averaged streamwise velocity inside the array reaches a constant value after an initial adjustment region in the submerged-array cases. For D/h ≥ 1.33, the mean normal velocities through the top and side faces of the array do not become equal to zero downstream of the initial adjustment region. The flow inside the array reaches an equilibrium regime where the local flux of fluid leaving the array through its side face is balanced by the local flux of fluid entering the array through its top face. This regime is observed until close to the end of the array. For D/h ≥ 2.0, the horizontal shear layer vortices do not generate successive regions of high and low streamwise velocity and bed friction velocity inside the array, as is observed in the emerged cases. With respect to the emerged case, the size of the shear layer vortices and the shear layer width increase for low submergence ratios before decreasing rapidly for D/h ≥ 1.33. Significant three-dimensional effects are present inside the array and the horizontal shear layer for cases with both emerged and submerged arrays. In the ϕ = 0.08 cases, strong upwelling and downwelling motions are observed inside the array for D/h ≥ 1.33, while the circulation of the streamwise-oriented cell of secondary flow forming close to the lateral face of the array peaks when the submergence ratio is close to 1.33. For constant ϕ, the total streamwise drag force normalized with the height and width of the array increases with increasing submergence ratio. As the array submergence increases, the cylinders near the front of the array contribute less to the total force acting on the cylinders forming the array. For constant D/h, the total streamwise drag force acting on the array increases with ϕ for the submerged and emerged cases.

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“…Understanding the nature of turbulent flow in vegetation is important in forestry, hydrology and agriculture. The relevance of scientific research to study the features of the formation and development of flow inside and near group structures of streamlined bodies is due to the search for more sustainable methods of environmental management, improvement of ecology and the use of natural resources, the development of weather and climate forecasting systems, as well as the need to study global biogeochemical cycles ( Lopes et al., 2015 ; Brunet, 2020 ; Koken and Constantinescu, 2021 ). For example, in channel streams, areas of vegetation improve water quality and habitat for fish.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, many studies have been carried out on the research of vortex and jet flows between single and group structures of bluff bodies and junction flows, both by numerical and experimental methods. RANS, DNS, LES and DES methods with various turbulence models k-ε, k-ω, k-g, SSD and others were used for numerical simulations ( Duraisamy et al., 2019 ; Rona et al., 2020 ; Chang et al., 2020 ; Chen et al., 2020a , 2020b ; Monti et al., 2020 ; Robison et al., 2021 ; Koken and Constantinescu, 2021 ; Hassan and Jalal, 2021 ; Zhao et al., 2022 ). Experimental studies of the fields of velocity, pressure, temperature and other parameters were carried out using a wide variety of sensors, measuring systems and equipment for recording, processing and analyzing data ( Bateni et al., 2019 ; Gautam et al., 2019 ; Galan et al., 2019 ; Hamed et al., 2019 ; Priyanka et al., 2019 ; Guan et al., 2019 ; Karimaei and Zarrati, 2019 ; Zuccarello et al., 2020 ; Yang et al., 2020 , 2021 ).…”

Section: Introductionmentioning

confidence: 99%

Junction flow inside and around three-row cylindrical group on rigid flat surface

Voskoboinick

Onyshchenko²,

Voskoboinyk³

et al. 2022

Heliyon

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Flow structure inside and around a rectangular array of rigid emerged cylinders located at the sidewall of an open channel

Abstract: Abstract

Cited by 21 publications

References 71 publications

Oscillatory flow around a vertical circular cylinder placed in an open channel: coherent structures, sediment entrainment potential and drag forces

Oscillatory flow around a vertical circular cylinder placed in an open channel: coherent structures, sediment entrainment potential and drag forces

Influence of submergence ratio on flow and drag forces generated by a long rectangular array of rigid cylinders at the sidewall of an open channel

Junction flow inside and around three-row cylindrical group on rigid flat surface

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