Hydraulic flow through a channel contraction: Multiple steady states

Akers, Benjamin F.; Bokhove, Onno

doi:10.1063/1.2909659

Cited by 41 publications

(51 citation statements)

References 17 publications

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“…1 U j , where h is the bore amplitude, and h u is the upstream water depth (e.g., Chaudhry 2007; Akers and Bokhove 2008;Defina and Viero 2010). It is appropriate to apply a similar extension to the internal oblique hydraulic jump.…”

Section: Oblique Hydraulic Jumpsmentioning

confidence: 99%

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Oblique Internal Hydraulic Jumps at a Stratified Estuary Mouth

Honegger

Haller

Geyer

et al. 2017

Journal of Physical Oceanography

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Observations and analyses of two tidally recurring, oblique, internal hydraulic jumps at a stratified estuary mouth (Columbia River, Oregon/Washington) are presented. These hydraulic features have not previously been studied due to the challenges of both horizontally resolving the sharp gradients and temporally resolving their evolution in numerical models and traditional observation platforms. The jumps, both of which recurred during ebb, formed adjacent to two engineered lateral channel constrictions and were identified in marine radar image time series. Jump occurrence was corroborated by (i) a collocated sharp gradient in the surface currents measured via airborne along-track interferometric synthetic aperture radar and (ii) the transition from supercritical to subcritical flow in the cross-jump direction via shipborne velocity and density measurements. Using a two-layer approximation, observed jump angles at both lateral constrictions are shown to lie within the theoretical bounds given by the critical internal long-wave (Froude) angle and the arrested maximum-amplitude internal bore angle, respectively. Also, intratidal and intertidal variability of the jump angles are shown to be consistent with that expected from the two-layer model, applied to varying stratification and current speed over a range of tidal and river discharge conditions. Intratidal variability of the upchannel jump angle is similar under all observed conditions, whereas the downchannel jump angle shows an additional association with stratification and ebb velocity during the low discharge periods. The observations additionally indicate that the upchannel jump achieves a stable position that is collocated with a similarly oblique bathymetric slope.

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Section: Oblique Hydraulic Jumpsmentioning

confidence: 99%

“…Further analytic and laboratory experimental work by Akers and Bokhove (2008) and Defina and Viero (2010) found good model/data agreement of observed jump angles when finite-amplitude effects were included. These effects increase the bore speed (and thereby decrease the corresponding jump angle).…”

Section: Introductionmentioning

confidence: 99%

Oblique Internal Hydraulic Jumps at a Stratified Estuary Mouth

Honegger

Haller

Geyer

et al. 2017

Journal of Physical Oceanography

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“…Consequently, a systematic study of the validity of the granular shallow-layer model is required. By respectively extending the "hydraulic" analysis for fluidised granular matter and water in Vreman et al [49] and Akers and Bokhove [1], granular flows within constrictions become an analytically-treatable target. Such flows in constrictions reach a steady state and appear (partially) accessible by direct DPM simulations.…”

Section: Open Questionsmentioning

confidence: 99%

Closure relations for shallow granular flows from particle simulations

et al. 2012

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The discrete particle method (DPM) is used to model granular flows down an inclined chute with varying basal roughness, thickness and inclination. We observe three major regimes: arresting flows, steady uniform flows and accelerating flows. For flows over a smooth base, other (quasi-steady) regimes are observed: for small inclinations the flow can be highly energetic and strongly layered in depth; whereas, for large inclinations it can be non-uniform and oscillating. For steady uniform flows, depth profiles of density, velocity and stress are obtained using an improved coarse-graining method, which provides accurate statistics even at the base of the flow. A shallow-layer model for granular flows is completed with macro-scale closure relations obtained from micro-scale DPM simulations of steady flows. We obtain functional relations for effective basal friction, velocity shape factor, mean density, and the normal stress anisotropy as functions of layer thickness, flow velocity and basal roughness. Granular avalanche flows are common in both the natural environments and industry. They occur across many orders of magnitude. Examples range from rock slides, containing upwards of 1,000 m 3 of material; to the flow of sinter, pellets and coke into a blast furnace for iron-ore melting; down to the flow of sand in an hour-glass. The dynamics of these flows are influenced by many factors such as: polydispersity; variations in density; non-uniform shape; complex basal topography; surface contact properties; coexistence of static, steady and accelerating material; and, flow obstacles and constrictions. KeywordsDiscrete particle methods (DPMs) are an extremely powerful way to investigate the effects of these and other factors. With the rapid recent improvement in computational power the full simulation of the flow in a small hour glass of millions of particles is now feasible. However, complete DPM simulations of large-scale geophysical mass flow will, probably, never be possible.One of the main goals of the present research is to simulate large scale and complex industrial flows using granular shallow-layer equations. In this paper we will take the first step of using the DPM [9,34,42,43,46] to simulate small granular flows of mono-dispersed spherical particles in steady flow situations. We will use a refined and novel analysis to investigate three particular aspects of shallow chute flows: (i) how to obtain meaningful macro-scale fields from the DPM simulation, (ii) how to assess the flow dependence on the basal roughness, and (iii) how to validate the assumptions made in depth-averaged theory.The DPM simulations presented here will enable the construction of the mapping between the micro-scale and 123

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“…They are classified according to the Froude number Fr which is the ratio of the inertial to gravitational forces, and can be viewed as the hydrodynamic equivalent of the Mach number for gas flows. Simplified hydraulic theories for one-phase shallow flows based on depth and crossaveraged approximations have been compared to experiments with both water (Akers and Bokhove 2008) and with dry granular material (Vreman et al 2007). The influence of bottleneck on the flow is different, depending on whether the upstream flow is sub or supercritical (Fr<1 and Fr>1 respectively), and on the width of the contraction relatively to the width of the chute.…”

Section: Introductionmentioning

confidence: 99%

Discrete element study of liquid-solid slurry flows through constricted channels

Abbas¹,

Hoef²,

Bokhove³

et al. 2010

AIP Conference Proceedings

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Discrete element model is used to simulate the flow of liquid-granule mixtures in an inclined channel containing a linear contraction. All the relevant particle/particle and particle/fluid interactions are included in the numerical model. The presence of the contraction induces different steady morphologies of the solid phase or the mixture depending on whether closed or open channels are used. These flows behave quite differently depending on the upstream Froude number and the contraction size ratio. The model is first validated by comparing with the existing results for dry granular (glass particles) chute flows (Vreman et al., 2007). Then simulations of a chute of glass particles in water flowing in a closed channel are compared to the dry granular case. With the same solid flux at the inlet, the hydrodynamic forces in the liquid-solid mixture induce higher particle solid volume fractions in the part of the flow containing the solid phase. The streamwise particle velocity (resp. depth of the solid phase) has the same evolution along the channel with smaller (larger) values than in the dry granular flow case.

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Hydraulic flow through a channel contraction: Multiple steady states

Cited by 41 publications

References 17 publications

Oblique Internal Hydraulic Jumps at a Stratified Estuary Mouth

Oblique Internal Hydraulic Jumps at a Stratified Estuary Mouth

Closure relations for shallow granular flows from particle simulations

Discrete element study of liquid-solid slurry flows through constricted channels

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