Experimental investigation of low-angle dune morphodynamics

Naqshband, Suleyman; Wullems, Bas; Ruijsscher, T.V. de; Hoitink, A.J.F.

doi:10.1051/e3sconf/20184002056

Cited by 3 publications

(2 citation statements)

References 11 publications

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“…Based on our results and previous research (e.g. Best and Kostaschuk, 2002;Bradley et al, 2013;Kwoll et al, 2016; Naqshband et al, 2018;Kostaschuk and Villard, 1996), properties of each dune category can be identified (Fig. 9).…”

Section: Low- Intermediate-and High-angle Dunessupporting

confidence: 57%

The influence of dune lee side shape on time-averaged velocities and turbulence

Lefebvre¹,

Cisneros²

2023

Earth Surf. Dynam.

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Abstract. Underwater dunes are found in various environments with strong hydrodynamics and movable sediment such as rivers, estuaries and continental shelves. They have a diversity of morphology, ranging from low- to high-angle lee sides and sharp or rounded crests. Here, we investigate the influence of lee side morphology on flow properties (time-averaged velocities and turbulence). To do so, we carried out a large number of numerical simulations of flow over dunes with a variety of morphologies using Delft3D. Our results show that the value of the mean lee side angle in addition to the value and position of the maximum lee side angle have an influence on the flow properties investigated. We propose a classification with the following three types of dunes: (1) low-angle dunes (mean lee side < 10∘), over which there is generally no flow separation and over which only little turbulence is created; (2) intermediate-angle dunes (mean lee side 10–17∘), over which an intermittent flow separation is likely over the trough; and (3) high-angle dunes (mean lee side > 17∘), over which the flow separates at the brink point and reattaches shortly after the trough and over which turbulence is high. The influence of maximum lee side slope value and position on flow characteristics depends on the dune type. We discuss the implications of the proposed dune classification on the interaction between dune morphology and flow.

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Section: Low- Intermediate-and High-angle Dunessupporting

confidence: 57%

The influence of dune lee side shape on time-averaged velocities and turbulence

Lefebvre¹,

Cisneros²

2023

Earth Surf. Dynam.

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“…One should be sure though to non-dimensionalise space and time with typical length and time scales to tune the weighting of the nearest neighbours in this three-dimensional LOESS approach. Although a numerical implementation is already available for an unlimited amount of dimensions, this has not been applied yet [Vermeulen, 2016].…”

Section: Future Research Directions 621 Bed Level Monitoringmentioning

confidence: 99%

Aligned with the flow : Morphodynamics in a river trained by longitudinal dam

Ruijsscher¹,

Victor²

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Effect of non‐migrating bars on dune dynamics in a lowland river

Ruijsscher

Naqshband

Hoitink

2020

Earth Surf Processes Landf

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As dunes and larger‐scale bed forms such as bars coexist in rivers, the question arises whether dune dynamics are influenced by interaction with the underlying bed topography. The present study aims to establish the degree to which dune characteristics in two and three dimensions are influenced by an underlying topography dominated by non‐migrating bars. As a case study, a 20 km stretch in the Waal River in the Netherlands is selected, which represents a sand‐bed lowland river. At this location, longitudinal training dams (LTDs) have recently been constructed to ensure sufficient navigation depth during periods with low water levels, and to reduce flood risk. By using data covering 2‐year‐long periods before and after LTD construction, the robustness of the results is investigated. Before LTD construction, dune characteristics show large variability both spatially and temporally, with dunes being longer, lower, less steep and having a lower lee side angle when they are located on bar tops. The correlation between dune characteristics and the underlying bed topography is disrupted by unsteady conditions for which the dunes are in a state of transition. The bar pattern causes tilting of dune crest lines, which may result from a transverse gradient in bedload sediment transport. As a result of LTD construction, the hydraulic and morphological conditions have changed significantly. Despite this, the main conclusions still hold, which strengthens the validity of the results. ©2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

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Experimental investigation of low-angle dune morphodynamics

Cited by 3 publications

References 11 publications

The influence of dune lee side shape on time-averaged velocities and turbulence

The influence of dune lee side shape on time-averaged velocities and turbulence

Aligned with the flow : Morphodynamics in a river trained by longitudinal dam

Effect of non‐migrating bars on dune dynamics in a lowland river

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