ORCID Profile
0000-0001-6154-3357
Current Organisations
University of Amsterdam
,
University of Oxford
,
Delft University of Technology
,
Technische Universiteit Delft
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Publications
Nonlinear wave evolution with data-driven breaking
Publisher: Springer Science and Business Media LLC
Date: 29-04-2022
DOI: 10.1038/S41467-022-30025-Z
Abstract: Wave breaking is the main mechanism that dissipates energy input into ocean waves by wind and transferred across the spectrum by nonlinearity. It determines the properties of a sea state and plays a crucial role in ocean-atmosphere interaction, ocean pollution, and rogue waves. Owing to its turbulent nature, wave breaking remains too computationally demanding to solve using direct numerical simulations except in simple, short-duration circumstances. To overcome this challenge, we present a blended machine learning framework in which a physics-based nonlinear evolution model for deep-water, non-breaking waves and a recurrent neural network are combined to predict the evolution of breaking waves. We use wave tank measurements rather than simulations to provide training data and use a long short-term memory neural network to apply a finite-domain correction to the evolution model. Our blended machine learning framework gives excellent predictions of breaking and its effects on wave evolution, including for external data.
Robust fast nonsingular terminal sliding mode control strategy for electronic throttle based on extreme learning machine
Publisher: IEEE
Date: 07-2019
The effect of bed roughness uncertainty on tidal stream power estimates for the Pentland Firth
Publisher: The Royal Society
Date: 2020
DOI: 10.1098/RSOS.191127
Abstract: Uncertainty affects estimates of the power potential of tidal currents, resulting in large ranges in values reported for sites such as the Pentland Firth, UK. Kreitmair et al. (2019, R. Soc. open sci. 6 , 180941. ( doi:10.1098/rsos.191127 )) have examined the effect of uncertainty in bottom friction on tidal power estimates by considering idealized theoretical models. The present paper considers the role of bottom friction uncertainty in a realistic numerical model of the Pentland Firth spanned by different fence configurations. We find that uncertainty in removable power estimates resulting from bed roughness uncertainty depends on the case considered, with relative uncertainty between 2% (for a fully spanned channel with small values of mean roughness and input uncertainty) and 44% (for an asymmetrically confined channel with high values of bed roughness and input uncertainty). Relative uncertainty in power estimates is generally smaller than (input) relative uncertainty in bottom friction by a factor of between 0.2 and 0.7, except for low turbine deployments and very high mean values of friction. This paper makes a start at quantifying uncertainty in tidal stream power estimates, and motivates further work for proper characterization of the resource, accounting for uncertainty inherent in resource modelling.
Experimental observation of a near-motion-trapped mode: free motion in heave with negligible radiation
Publisher: Cambridge University Press (CUP)
Date: 02-12-2015
DOI: 10.1017/JFM.2015.669
Abstract: A simple geometry that exhibits near motion trapping is tested experimentally, along with perturbed versions of the structure. The motion of the freely floating structure and the surrounding wave field is tracked and the near-motion-trapped mode is found, characterised by a slowly decaying heave motion with very small linear radiation of energy. It is found that the latter property is a better discriminator of the perturbed geometries as viscous d ing masks fine differences in radiation d ing as far as the motion of the structure is concerned. The magnitude of this viscous d ing is reasonably well predicted by a simple Stokes oscillatory boundary layer analysis.
Hydrodynamic
X
Publisher: American Physical Society (APS)
Date: 29-10-2019
The effect of uncertain bottom friction on estimates of tidal current power
Publisher: The Royal Society
Date: 2019
DOI: 10.1098/RSOS.180941
Abstract: Uncertainty affects estimates of the power potential of tidal currents, resulting in large ranges in values reported for a given site, such as the Pentland Firth, UK. We examine the role of bottom friction, one of the most important sources of uncertainty. We do so by using perturbation methods to find the leading-order effect of bottom friction uncertainty in theoretical models by Garrett & Cummins (2005 Proc. R. Soc. A 461 , 2563–2572. ( doi:10.1098/rspa.2005.1494 ) 2013 J. Fluid Mech. 714 , 634–643. ( doi:10.1017/jfm.2012.515 )) and Vennell (2010 J. Fluid Mech. 671 , 587–604. ( doi:10.1017/S0022112010006191 )), which consider quasi-steady flow in a channel completely spanned by tidal turbines, a similar channel but retaining the inertial term, and a circular turbine farm in laterally unconfined flow. We find that bottom friction uncertainty acts to increase estimates of expected power in a fully spanned channel, but generally has the reverse effect in laterally unconfined farms. The optimal number of turbines, accounting for bottom friction uncertainty, is lower for a fully spanned channel and higher in laterally unconfined farms. We estimate the typical magnitude of bottom friction uncertainty, which suggests that the effect on estimates of expected power lies in the range −5 to +30%, but is probably small for deep channels such as the Pentland Firth (5–10%). In such a channel, the uncertainty in power estimates due to bottom friction uncertainty remains considerable, and we estimate a relative standard deviation of 30%, increasing to 50% for small channels.
Directional soliton and breather beams
Publisher: Proceedings of the National Academy of Sciences
Date: 26-04-2019
Abstract: Understanding the fundamental dynamics of directional and localized waves is of significant importance for modeling ocean waves as well as predicting extreme events. We report a theoretical framework, based on the universal (2D + 1) nonlinear Schrödinger equation, that allows the construction of slanted solitons and breathers on the water surface. Our corresponding wave flume observations emphasize and uniquely reveal that short-crested localizations can be described as a result of nonlinear wave dynamics, complementing the linear superposition and interference arguments as has been generally suggested for directional ocean waves.
The physical oceanography of the transport of floating marine debris
Publisher: IOP Publishing
Date: 02-2020
Abstract: Marine plastic debris floating on the ocean surface is a major environmental problem. However, its distribution in the ocean is poorly mapped, and most of the plastic waste estimated to have entered the ocean from land is unaccounted for. Better understanding of how plastic debris is transported from coastal and marine sources is crucial to quantify and close the global inventory of marine plastics, which in turn represents critical information for mitigation or policy strategies. At the same time, plastic is a unique tracer that provides an opportunity to learn more about the physics and dynamics of our ocean across multiple scales, from the Ekman convergence in basin-scale gyres to in idual waves in the surfzone. In this review, we comprehensively discuss what is known about the different processes that govern the transport of floating marine plastic debris in both the open ocean and the coastal zones, based on the published literature and referring to insights from neighbouring fields such as oil spill dispersion, marine safety recovery, plankton connectivity, and others. We discuss how measurements of marine plastics (both in situ and in the laboratory), remote sensing, and numerical simulations can elucidate these processes and their interactions across spatio-temporal scales.
Related Organisations
The University Of Edinburgh
Location: United Kingdom of Great Britain and Northern Ireland
University Of Oxford
Location: United Kingdom of Great Britain and Northern Ireland
Related Funding Activities
No related grants have been discovered for T. S. van den Bremer.