Secondary Flow in Mildly Sinuous Channel

Johannesson, Helgi; Parker, Gary

doi:10.1061/(asce)0733-9429(1989)115:3(289)

Cited by 123 publications

(92 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The adaptation length of the centre-region cell of secondary flow scales with C f -1 H (e.g. Rozovskii, 1957;de Vriend, 1981;Johannesson and Parker, 1989). The shallower flow and the rougher bed in the mobile-bed experiment reduce the effect of remnant cells from the upstream bend.…”

Section: Three-dimensional Flow Featuresmentioning

confidence: 99%

Flow separation at the inner (convex) and outer (concave) banks of constant‐width and widening open‐channel bends

Blanckaert

Kleinhans

McLelland

et al. 2012

Earth Surf Processes Landf

100

View full text Add to dashboard Cite

There is a paucity of data and insight in the mechanisms of, and controls on flow separation and recirculation at natural sharply-curved river bends. Herein we report on successful laboratory experiments that elucidate flow structure in one constant-width bend and a second bend with an outer-bank widening. The experiments were performed with both a flat immobile gravel bed and mobile sand bed with dominant bedload sediment transport.In the constant-width bend with immobile bed, a zone of mainly horizontal flow separation (vertical rotational axis) formed at the inner bank that did not contain detectable flow recirculation, and an outer-bank cell of secondary flow with streamwise oriented rotational axis. Surprisingly, the bend with widening at the outer bank and immobile bed did not lead to a transverse expansion of the flow. Rather, flow in the outer-bank widening weakly recirculated around a vertical axis and hardly interacted with the inner part of the bend, which behaved as a constant-width bend.In the mobile bed experiment, downstream of the bend apex a pronounced depositional bar developed at the inside of the bend and pronounced scour occurred at the outside. Moreover the deformed bed promoted flow separation over the bar, including return currents. In the constant-width bend, the topographic steering impeded the generation of an outer-bank cell of secondary flow. In the bend with outer-bank widening, the topographic steering induced an outward expansion of the flow, whereby the major part of the discharge was conveyed in the central part of the widening section. Flow in the outer-bank widening was highly three dimensional and included return currents near the bottom.In conclusion, the experiments elucidated three distinct processes of flow separation common in sharp bends: flow separation at the inner bank, an outer-bank cell of secondary flow, and flow separation and recirculation in an outer-bank widening.

show abstract

Section: Three-dimensional Flow Featuresmentioning

confidence: 99%

Flow separation at the inner (convex) and outer (concave) banks of constant‐width and widening open‐channel bends

Blanckaert

Kleinhans

McLelland

et al. 2012

Earth Surf Processes Landf

100

View full text Add to dashboard Cite

show abstract

“…Engelund, 1974;Ikeda, 1975;de Vriend, 1977;Johannesson and Parker, 1989a). These models are invariantly based on mild-curvature assumptions, implying that R/B and R/H are sufficiently large and that the curvature radius varies slowly in streamwise direction.…”

Section: Introductionmentioning

confidence: 99%

“…van Bendegom, 1947;Rozovskii, 1957;Engelund, 1974;Ikeda, 1975;de Vriend, 1977;Johannesson and Parker, 1989a). The nonlinear hydrodynamic interactions between the secondary flow and the streamwise flow are parameterized by means of the correction factor 〈v s v n 〉 ∞ /〈v s v n 〉 0 = fct(β), which uniquely depends on the so-called bend parameter (Blanckaert and de Vriend, 2003):…”

Section: Introductionmentioning

confidence: 99%

Processes governing the flow redistribution in sharp river bends

2012

View full text Add to dashboard Cite

Insight is provided in hydrodynamic processes governing the velocity redistribution in sharp river bends based on simulations of three recent experiments by means of Blanckaert and de Vriend's (2003Vriend's ( , 2010 reduced-order nonlinear model without curvature restrictions. This model successfully simulated the flow redistribution and the secondary flow in all three experiments. The results indicate that the flow redistribution is primarily governed by topographic steering, curvature variations and secondary flow, in a broad range of different configurations, including mildly to sharply curved bends, narrow to shallow bends, smooth to rough bends, bends with additional complexities such as horizontal recirculation zones or patches of riverbed vegetation. The relative importance of these three dominant processes is case dependent, and controlled by the parameters C f − 1 H/B, R/B and streamwise curvature variations. The first parameter characterizes a river reach, whereas the second and third parameters are characteristics of individual bends. Major differences exist between the hydrodynamic processes in mildly and sharply curved bends. First, velocity redistribution induced by curvature variations is negligible in mildly curved bends, but the dominant process in sharp bends. This result is relevant, because most meander models are based on the assumption of weak-curvature variations. Second, nonlinear hydrodynamic interactions play a dominant role in sharp bends, where mild-curvature models overpredict the secondary flow and in some cases even falsely identify it as the dominant process governing the velocity redistribution, which leads to unsatisfactory flow predictions. The reduction in secondary flow strength provoked by the nonlinear hydrodynamic interactions is accompanied by a reduction in the transverse bed slope, which reduces the effect of topographic steering.

show abstract

“…Some studies analyse meander development and instability from an analytical point of view [10][11][12][13] or they search for an equilibrium solution under certain conditions [14]. Others focus on the local curvature-induced effects [15], which generate a secondary current, consisting in an outwards motion near the water surface and an inwards motion at the bottom, perpendicular to the main flow [8].…”

Section: Introductionmentioning

confidence: 99%

Numerical Modelling of Cohesive Bank Migration

Bosa

Petti

Pascolo

2018

Water

View full text Add to dashboard Cite

River morphological evolution is a challenging topic, involving hydrodynamic flow, sediment transport and bank stability. Lowland rivers are often characterized by the coexistence of granular and cohesive material, with significantly different behaviours. This paper presents a bidimensional morphological model to describe the evolution of the lower course of rivers, where there are both granular and cohesive sediments. The hydrodynamic equations are coupled with two advection-diffusion equations, which consider the transport of granular and cohesive suspended sediment concentration separately. The change of bed height is evaluated as the sum of the contributions of granular and sediment material. A bank failure criterion is developed and incorporated into the numerical simulation of the hydrodynamic flood wave and channel evolution, to describe both bed deformation and bank recession. To this aim, two particular mechanisms are considered: the former being a lateral erosion due to the current flow and consequent cantilever collapse and the latter a geostatic failure due to the submergence. The equation system is integrated by means of a finite volume scheme. The resulting model is applied to the Tagliamento River, in northern Italy, where the meander migration is documented through a sequence of aerial images. The channel evolution is simulated, imposing an equivalent hydrograph consisting of a sequence of flood waves, which represents a medium year, with reference to their effect on sediment transport. The results show that the model adequately describes the general morphological evolution of the meander.

show abstract

Secondary Flow in Mildly Sinuous Channel

Cited by 123 publications

References 8 publications

Flow separation at the inner (convex) and outer (concave) banks of constant‐width and widening open‐channel bends

Flow separation at the inner (convex) and outer (concave) banks of constant‐width and widening open‐channel bends

Processes governing the flow redistribution in sharp river bends

Numerical Modelling of Cohesive Bank Migration

Contact Info

Product

Resources

About