Turbulence Characteristics of Flows Through Partially and Fully Submerged Vegetation

Fairbanks, Jonathan Dean; Diplas, Panayiotis

doi:10.1061/40382(1998)144

Cited by 15 publications

(13 citation statements)

References 6 publications

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“…Modified k-ε or k-ω turbulence closure models were used, introducing drag-related sink terms into the turbulent transport equations. Laboratory experiments by Dunn et al (1996), Tsujimoto and Kitamura (1998), Fairbanks and Diplas (1998) and Pasche and Rouve (1985) were used to validate the models. Naot et al (1996) and Choi and Kang (2001) used a higher order anisotropic turbulence closure, the Reynold's Stress model (RSM), to simulate the flow through rigid submerged vegetation elements.…”

Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Turbulent Flow Through Submerged Vegetation

et al. 2009

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Large Eddy Simulations (LES) are performed for an open channel flow through idealized submerged vegetation with a water depth (h) to plant height (h p ) ratio of h/ h p = 1.5 according to the experimental configuration of Liu et al. (J Geophys Res Earth Sci, 2008).They used a 1D laser Doppler velocimeter (LDV) to measure longitudinal and vertical velocities as well as turbulence intensities along several verticals in the flow and the data are used for the validation of the present simulations. The code MGLET is used to solve the filtered Navier-Stokes equations on a Cartesian non-uniform grid. In order to represent solid objects in the flow, the immersed boundary method is employed. The computational domain is idealized with a box containing 16 submerged circular cylinders and periodic boundary conditions are applied in both longitudinal and transverse directions. The predicted streamwise as well as vertical mean velocities are in good agreement with the LDV measurements. Furthermore, fairly good agreement is found between calculated and measured streamwise and vertical turbulence intensities. Large-scale flow structures of different shapes are present in the form of vortex rolls above the vegetation tops as well as locally generated trailing and vonKarman-type vortices due to flow separation at the free end and the sides of the cylinders. In this paper, the flow field is analyzed statistically and evidence is provided for the existence of these structures based on the LES.

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Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Turbulent Flow Through Submerged Vegetation

et al. 2009

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“…Turbulence strongly affects many hydraulic processes, including, velocity distribution, mixing, diffusivity, contaminant transport, bed shear stress, scour or sediment transport, and energy dissipation. [1][2][3][4] However, turbulence itself is affected by the nature of the channel cross section.…”

Section: Introductionmentioning

confidence: 99%

“…This change strongly affects the hydrodynamic flow structures, including turbulence intensities and Reynolds shear stresses. For emergent vegetation, research 11 indicated that the mean velocity profile consists of two basic regions: a bed-surface boundary layer in which the flow is dominated by bed generated shear and an upper region in which the mean velocity remains fairly constant with height. Just above the viscous sublayer, the mean velocity profile is influenced by both bed generated turbulence and wake generated turbulence.…”

Section: Introductionmentioning

confidence: 99%

Prediction of channel flow characteristics through square arrays of emergent cylinders

Meftah

Mossa

2013

Physics of Fluids

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This paper describes a theoretical approach of turbulent flow in an infinite square array of emergent cylinders distributed uniformly along a channel bottom. Laboratory experiments were carried out to investigate the flow velocity characteristics in order to confirm this theoretical approach. A model array of vertical, rigid, circular, and threaded steel cylinders, of regular distribution, was mounted on the bed of a recirculating hydraulic channel. Measurements of the three-dimensional flow velocity components were carried out using a 3D acoustic Doppler velocimeter. At a certain distance downstream of a lateral row of cylinders, the transversal profiles of velocities and turbulence parameters are expected to be periodic functions in the lateral position whose period is the centre-to-centre spacing of two side-by-side cylinders. Some empirical expressions for predicting the turbulent flow features have been established. The formulation proposed is consistent with the experimental data over a certain range of the Reynolds number based on the cylinder diameter. In addition, a new formula to estimate the bulk drag coefficient $\overline {C_D }$CD¯ of the array of cylinders is proposed and validated.

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“…Moreover, the calculated base pressure ( pb C  =0.93) that is a good indicator of whether the pressure in the wake is correct lies within the experimental range of values (0.83-0.93). Taking into account that at ReD=3900 the largest contribution to drag is the pressure drag arising from the wake downstream of the cylinder (Fairbanks, 1998), the overall drag is expected to be well predicted by the SAS. As expected, the distribution of pressure with URANS coincides with that of SAS up to Θ=120 ο , because according to Figure 7 URANS is used in this region by both models.…”

Section: Distribution Of Pressure (P)mentioning

confidence: 99%

“…Total drag force. The total drag force acting on the cylinder surface in the axial direction is the sum of the drag force caused by pressure differences on either side of the cylinder, and the friction drag caused by shear stresses (Fairbanks, 1998). The average value of the drag coefficient (CD) was determined by equation ( 3.…”

Section: Distribution Of Pressure (P)mentioning

confidence: 99%

Modeling the 3-d flow around a cylinder using the SAS hybrid model

2014

Global NEST Journal

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Three-dimensional calculations were performed to simulate the flow around a cylindrical vegetation element using the Scale Adaptive Simulation (SAS) model; commonly, this is the first step of the modeling of the flow through multiple vegetation elements. SAS solves the Reynolds Averaged NavierStokes equations in stable flow regions, while in regions with unstable flow it goes unsteady producing a resolved turbulent spectrum after reducing eddy viscosity according to the locally resolved vortex size represented by the von Karman length scale. A finite volume numerical code was used for the spatial discretisation of the rectangular computational domain with stream-wise, cross-flow and vertical dimensions equal to 30D, 11D and 1D, respectively, which was resolved with unstructured grids. Calculations were compared with experiments and Large Eddy Simulations (LES). Predicted overall flow parameters and mean flow velocities exhibited a very satisfactory agreement with experiments and LES, while the agreement of predicted turbulent stresses was satisfactory. Calculations showed that SAS is an efficient and relatively fast turbulence modeling approach, especially in relevant practical problems, in which the very high accuracy that can be achieved by LES at the expense of large computational times is not required.

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Turbulence Characteristics of Flows Through Partially and Fully Submerged Vegetation

Cited by 15 publications

References 6 publications

Large Eddy Simulation of Turbulent Flow Through Submerged Vegetation

Large Eddy Simulation of Turbulent Flow Through Submerged Vegetation

Prediction of channel flow characteristics through square arrays of emergent cylinders

Modeling the 3-d flow around a cylinder using the SAS hybrid model

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