Unsteady dynamics of turbulent flow in the wakes of barchan dunes modulated by overlying boundary-layer structure

Abstract

Abstract

Local Similarity Between Aeolian Barchan Dunes and Their Downsized Subaqueous Counterparts

“…Bristow et al. (2020, 2021) measured the water flow structure of two off‐centered fixed barchan dune models by particle imaging velocimetry (PIV), and the results are basically consistent with the large eddy simulation results of C. Wang et al. (2016).…”

“…The length of the vortex zone A is about 4H, the length of the protection zone B is about 1∼2H, and the length of the wake recovery zone C is about 9∼10H, where H is the dune height. Bristow et al (2020Bristow et al ( , 2021 measured the water flow structure of two off-centered fixed barchan dune models by particle imaging velocimetry (PIV), and the results are basically consistent with the large eddy simulation results of C. Wang et al (2016). Bristow et al (2018Bristow et al ( , 2019) used a two-point velocity correlation coefficient to identify the coherent flow structure in space in a statistical sense.…”

Topographic perturbation of turbulent boundary layers by low‐angle, early‐stage aeolian dunes

“…These studies have focused on quantifying the relationships that exist between dune form, airflow perturbations, sand flux, and the subsequent impact of erosion and deposition on dune dynamics. Measurements of flow perturbation over aeolian and subaqueous dunes in both experiments and field environments have revealed the influence of topographic steering by dune morphology on both mean and turbulent flow (Baddock et al., 2011; Bristow et al., 2018, 2020, 2021; Maddux, McLean, & Nelson, 2003; Maddux, Nelson, & McClean, 2003; McKenna Neuman et al., 1997; Neuman et al., 2000; Walker & Nickling, 2002; Wiggs & Weaver, 2012), and have promoted an understanding of how these forced flow patterns may influence dune migration and growth by driving patterns of sand flux (Bennett & Best, 1995; Best, 2005; Claudin et al., 2013; Weaver and Wiggs, 2011). Studies on the dynamics of mature aeolian dunes have encouraged interest in the development of early‐stage dunes, with research examining the controls on the growth of nascent aeolian protodunes into mature dune forms (Baddock et al., 2018; Delorme et al., 2020; Elbelrhiti, 2012; Gadal et al., 2020; Nield, 2011; Nield et al., 2011; Qian et al 2021…”

“…and turbulent flow (Baddock et al, 2011;Bristow et al, 2018Bristow et al, , 2020Bristow et al, , 2021Maddux, Nelson, & McClean, 2003;McKenna Neuman et al, 1997;Neuman et al, 2000;Walker & Nickling, 2002;Wiggs & Weaver, 2012), and have promoted an understanding of how these forced flow patterns may influence dune migration and growth by driving patterns of sand flux (Bennett & Best, 1995;Best, 2005;Claudin et al, 2013;Weaver and Wiggs, 2011). Studies on the dynamics of mature aeolian dunes have encouraged interest in the development of early-stage dunes, with research examining the controls on the growth of nascent aeolian protodunes into mature dune forms (Baddock et al, 2018;Delorme et al, 2020;Elbelrhiti, 2012;Gadal et al, 2020;Nield, 2011;Nield et al, 2011;Qian et al2021).…”

“…The aim of the work presented herein is to quantify this flow-form coupling in key protodune development stages by leveraging a refractive-indexmatching approach in a laboratory flume environment. This methodology has been demonstrated in recent work to provide high-resolution near-surface flow measurements over complex 3D geometries (Blois et al, 2020;Bristow et al, 2018Bristow et al, , 2019Bristow et al, , 2020Bristow et al, , 2021Kim et al, 2020) by mitigating the obscuring effects of laser reflections during measurements and providing unimpeded optical access for non-intrusive flow quantification with particle image velocimetry (PIV). It is important to note, however, that no sediment transport occurs in this flume environment, and instead the focus is on the flow-form interaction alone utilizing fixed-bed models.…”