Near-bed hydrodynamics and turbulence below a large-scale plunging breaking wave over a mobile barred bed profile

Funded by The research presented in this paper is part of the SINBAD project. Grant Number: STW (12058) and EPSRC (EP/J00507X/1, EP/J005541/1)Peer reviewedPublisher PDFPublisher PD

Suspended sediment transport around a large-scale laboratory breaker bar

The authors wish to thank the staff of CIEMLAB (Joaquim Sospedra, Oscar Galego and Ricardo Torres) and Mick Poppe from the University of Twente for their contributions to the experiments. We are also grateful to fellow SINBAD researchers and to prof. Peter Thorne for their feedback on preliminary results and to two anonymous reviewers and prof. dr. Suzanne J.M.H. Hulscher for their feedback on the draft manuscript. The research presented in this paper is part of the SINBAD project, funded by STW (12058) and EPSRC (EP/J00507X/1, EP/J005541/1). We further acknowledge the European Community’s FP7 project Hydralab IV (contract no. 261520) for funding the accompanying SandT-Pro experiments and the ACVP development by CNRS-LEGI (D. Hurther, P.-A. Barraud, J.-M. Barnoud).Peer reviewedPostprin

Wave Boundary Layer Hydrodynamics and Sheet Flow Properties under Large-Scale Plunging-Type Breaking Waves

The authors wish to thank the staff of CIEMLAB, in particular Joaquim Sospedra, Oscar Galego and Ricardo Torres, for their hospitality and hard work during the experimental campaign. This research was funded by the European Community’s Horizon 2020 Programme through the Integrated Infrastructure Initiative HYDRALAB+ COMPLEX (no. 654110), the French DGA funded ANR Astrid Maturation project MESURE (no. ANR-16- ASMA-0005-01) and the SINBAD project funded by STW (12058) in the Netherlands and by EPSRC (EP/J00507X/1, EPJ005541/1) in the UK. Data of this study are available at U. Twente repository doi (10.4121/uuid:753f1d84-36e5-47fa-b74b-55c288545b9b). Comments and remarks raised by the two anonymous reviewers helped to improve the quality of the paper.Peer reviewedPublisher PD

Observations of velocities, sand concentrations, and fluxes under velocity-asymmetric oscillatory flows

Peer reviewedPublisher PD

Bias in mean velocities and noise in variances and covariances measured using a multistatic acoustic profiler: The Nortek Vectrino Profiler

This paper compiles the technical characteristics and operating principles of the Nortek Vectrino Profiler and reviews previously reported user experiences. A series of experiments are then presented that investigate instrument behaviour and performance, with a particular focus on variations within the profile. First, controlled tests investigate the sensitivity of acoustic amplitude (and Signal-to-Noise Ratio, SNR) and pulse-to-pulse correlation coefficient, R2, to seeding concentration and cell geometry. Second, a novel methodology that systematically shifts profiling cells through a single absolute vertical position investigates the sensitivity of mean velocities, SNR and noise to: (a). emitted sound intensity and the presence (or absence) of acoustic seeding; and (b). varying flow rates under ideal acoustic seeding conditions. A new solution is derived to quantify the noise affecting the two orthogonal tristatic systems of the Vectrino Profiler and its contribution to components of the Reynolds stress tensor. Results suggest that for the Vectrino Profiler: 1. optimum acoustic seeding concentrations are ~3,000 to 6,000 mg L-1; 2. mean velocity magnitudes are biased by variable amounts in proximal cells but are consistently underestimated in distal cells; 3. noise varies parabolically with a minimum around the "sweet spot", 50 mm below the transceiver; 4. the receiver beams only intersect at the sweet spot and diverge nearer to and further from the transceiver. This divergence significantly reduces the size of the sampled area away from the sweet spot, reducing data quality; 5. the most reliable velocity data will normally be collected in the region between approximately 43 and 61 mm below the transceiver

Turbulence in Rivers

The study of turbulence has always been a challenge for scientists working on geophysical flows. Turbulent flows are common in nature and have an important role in geophysical disciplines such as river morphology, landscape modeling, atmospheric dynamics and ocean currents. At present, new measurement and observation techniques suitable for fieldwork can be combined with laboratory and theoretical work to advance the understanding of river processes. Nevertheless, despite more than a century of attempts to correctly formalize turbulent flows, much still remains to be done by researchers and engineers working in hydraulics and fluid mechanics. In this contribution we introduce a general framework for the analysis of river turbulence. We revisit some findings and theoretical frameworks and provide a critical analysis of where the study of turbulence is important and how to include detailed information of this in the analysis of fluvial processes. We also provide a perspective of some general aspects that are essential for researchers/ practitioners addressing the subject for the first time. Furthermore, we show some results of interest to scientists and engineers working on river flows

Experimental study of sheet flow regime of sediment transport in a laboratory flume.

International audienc

Controversial turbulent Schmidt number value in particle-laden boundary layer flows

International audienc