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Your search keyword '"Deleersnijder, Eric"' showing total 332 results
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332 results on '"Deleersnijder, Eric"'

10. Estimating Effective Light Exposure by Property-Tracking Tracers.

Author

Gross, Edward, Holleman, Rusty, Deleersnijder, Eric, and Delhez, Eric J. M.

Subjects
PHYTOPLANKTON, TURBIDITY
Abstract

A numerical approach to estimating the mean exposure of a tracer to a scalar property is applied to predict the light exposure of sinking phytoplankton. In our application, effective light exposure is defined as the time integral of a light limitation factor commonly used in phytoplankton models. Solutions from an adjoint approach have previously been published for a set of one-dimensional sinking phytoplankton scenarios. We illustrate that a simple extension to a standard advection–diffusion model produces similar results. Specifically, we present numerical solutions using property tracking in a one-dimensional advection–diffusion model for multiple tracers. Solutions are calculated for a range of eddy diffusivity distributions and compared with the published solutions. The consistency of the numerical solutions with the published solutions provides validation of the property-tracking approach. While the adjoint method solution is much less computationally intensive for the test cases, the property-tracking approach can be applied in multidimensional time-varying applications with an arbitrary distribution of sinking speed, diffusivity, and turbidity for which an adjoint solution has not been developed. Our intention is for this example application and corroboration of the "property-tracking" approach to inspire readers to envision additional applications for this approach. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Numerical computation of the residence time related to the water renewal in the Nador Lagoon.

Author

Oubarka, Ismail, Kissami, Imad, Elmahi, Imad, and Deleersnijder, Eric

Subjects
ADVECTION-diffusion equations, LAGOONS, WATER depth, TRANSPORT equation, BIOLOGICAL transport, DWELLINGS
Abstract

In this work, an unstructured finite volume solver is used to compute the residence time in the Nador lagoon (Morocco). The modeling system consists of the well-established shallow water system including the bathymetric forces, friction terms, Cori-olis forces, wind stress, and momentum diffusion terms. To model the passive tracer transport an advection-diffusion equation is used. The solver is based on a Non-Homogeneous Riemann solver that can handle topography variations. The objective of this study is to compute the mean residence time in the Nador lagoon considering several scenarios with respect to the pass between the Mediterranean Sea and the Nador lagoon. In particular, we propose a new inlet that can substantially reduce the water residence time in the lagoon. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Lagrangian ocean analysis: Fundamentals and practices

Author

van Sebille, Erik, Griffies, Stephen M., Abernathey, Ryan, Adams, Thomas P., Berloff, Pavel, Biastoch, Arne, Blanke, Bruno, Chassignet, Eric P., Cheng, Yu, Cotter, Colin J., Deleersnijder, Eric, Döös, Kristofer, Drake, Henri F., Drijfhout, Sybren, Gary, Stefan F., Heemink, Arnold W., Kjellsson, Joakim, Koszalka, Inga Monika, Lange, Michael, Lique, Camille, MacGilchrist, Graeme A., Marsh, Robert, Mayorga Adame, C. Gabriela, McAdam, Ronan, Nencioli, Francesco, Paris, Claire B., Piggott, Matthew D., Polton, Jeff A., Rühs, Siren, Shah, Syed H.A.M., Thomas, Matthew D., Wang, Jinbo, Wolfram, Phillip J., Zanna, Laure, and Zika, Jan D.

Published
2018
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18. Tides in Coastal Seas. Influence of Topography and Bottom Friction

Author

Roos, Pieter C., De Swart, Huib E., Schuttelaars, Henk, Heemink, Arnold, Deleersnijder, Eric, and Marine and Fluvial Systems

Subjects
22/4 OA procedure
Abstract

Tides are important in various ways, e.g., by affecting navigation and coastal safety and by acting as a driver for sediment transport and seabed dynamics. To explain spatial patterns of tidal phase and range, observed in coastal seas around the world, we present an idealised process-based model. It solves the depth-averaged linearised shallow water equations, including the Coriolis effect and bottom friction, on schematised geometries with rectilinear coastlines and stepwise topographic variations. Based on an extended Klein-Gordon equation (accounting for bottom friction), Kelvin and Poincaré modes are identified as the fundamental wave solutions in a channel of uniform width and depth. We analyse their spatial structures and dynamic properties, addressing the roles of bottom friction and transverse topographic steps. The solution for a semi-enclosed basin, including topographic steps, is then obtained as a superposition of these wave modes, by applying a collocation technique. As an example, we present solutions that grossly explain the amphidromic system of the Gulf of California. Finally, we discuss the modelling approach and address the links with morphodynamics and climate change.

Published
2022

20. The Multi-Channel System of the Vietnamese Mekong Delta: Impacts on the Flow Dynamics under Relative Sea-Level Rise Scenarios.

Author

Le, Hoang-Anh, Nguyen, Thong, Gratiot, Nicolas, Deleersnijder, Eric, and Soares-Frazão, Sandra

Subjects
ABSOLUTE sea level change, HYDRAULIC models, TIME-varying networks, FLOODPLAINS, SURFACE area
Abstract

The Mekong Delta has the world's third-largest surface area. It plays an indisputable role in the economy and livelihoods of Vietnam and Cambodia, with repercussions at regional and global scales. During recent decades, the Vietnamese part of the Mekong Delta underwent profound human interventions (construction of dykes and multi-channel networks), which modified the hydrodynamic regime, especially cycles of field submersion. In this study, we first applied a full 2D numerical hydraulic model, TELEMAC-2D, to examine the effects of the complex channel and river networks on the spatial and temporal distribution of the flow in the 40,000 km2 of the Vietnamese Mekong Delta. Then, two scenarios of relative sea-level rise in 2050 and 2100 were implemented to simulate the future patterns of water fluxes in the delta. The results show that dykes and multi-channel networks would reduce the inundation area by 36% and lessen the peak water level by 15% and the discharge over the floodplains by 24%. Despite this protection, under a relative sea-level rise of 30 cm and 100 cm, the maximum flooded area could occupy about 69% and 85% of the whole delta in 2050 and 2100, respectively. [ABSTRACT FROM AUTHOR]

Published
2023
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21. Diagnostic timescales in fluid flows: from partial differential equations to simple models

Author

Deleersnijder, Eric, Mouchet, Anne, Delhez, Eric JM, and UCL - SST/IMMC/MEMA - Applied mechanics and mathematics

Subjects
age, geophysical and environmental flows, residence/exposure time, reactive transport, CART (Constituent-oriented Age and Residence time Theory), diagnostic timescale
Abstract

For geophysical and environmental flows, diagnostic timescales (e.g., age, residence/exposure time) may be obtained at any time and position by solving the partial differential equations established in the framework of CART (Constituent-oriented Age and Residence time Theory, www.climate.be/cart). Such timescales are holistic in that they take into account in the whole domain of interest (advective and diffusive) transport as well as reactive processes. They may be instrumental in the development of reduced-complexity models such as a well-mixed box and various types of pipe flows (or a combination of such idealizations), aiming at interpreting the results of complex models. Illustrations are provided, focusing on the global water age distribution in the World Ocean, the top layer of Lake Tanganyika and the Scheldt Estuary. Clearly, diagnostic timescales paint a picture of the functioning of numerical models of reactive transport that is different from that obtained by analyzing primitive variables.

Published
2023

31. Simulating Lagrangian Subgrid‐Scale Dispersion on Neutral Surfaces in the Ocean

Author

Reijnders, Daan, Deleersnijder, Eric, van Sebille, Erik, Sub Physical Oceanography, Marine and Atmospheric Research, Sub Physical Oceanography, and Marine and Atmospheric Research

Subjects
Global and Planetary Change, Scale (ratio), Turbulence, diffusion, Mesoscale meteorology, Markov models, Earth and Planetary Sciences(all), Eulerian path, Mechanics, Eddy diffusion, subgrid-scale, Physics::Fluid Dynamics, symbols.namesake, Eddy, symbols, General Earth and Planetary Sciences, Environmental Chemistry, dispersion, neutral surfaces, 14. Life underwater, Diffusion (business), Dispersion (water waves), Geology, Physics::Atmospheric and Oceanic Physics, Lagrangian
Abstract

To capture the effects of mesoscale turbulent eddies, coarse-resolution Eulerian ocean models resort to tracer diffusion parameterizations. Likewise, the effect of eddy dispersion needs to be parameterized when computing Lagrangian pathways using coarse flow fields. Dispersion in Lagrangian simulations is traditionally parameterized by random walks, equivalent to diffusion in Eulerian models. Beyond random walks, there is a hierarchy of stochastic parameterizations, where stochastic perturbations are added to Lagrangian particle velocities, accelerations, or hyper-accelerations. These parameterizations are referred to as the first, second and third order "Markov models" (Markov-N), respectively. Most previous studies investigate these parameterizations in two-dimensional setups, often restricted to the ocean surface. On the other hand, the few studies that investigated Lagrangian dispersion parameterizations in three dimensions, where dispersion is largely restricted to neutrally buoyant surfaces, have focused only on random walk (Markov-0) dispersion. Here, we present a three-dimensional isoneutral formulation of the Markov-1 model. We also implement an anisotropic, shear-dependent formulation of random walk dispersion, originally formulated as a Eulerian diffusion parameterization. Random walk dispersion and Markov-1 are compared using an idealized setup as well as more realistic coarse and coarsened (50 km) ocean model output. While random walk dispersion and Markov-1 produce similar particle distributions over time when using our ocean model output, Markov-1 yields Lagrangian trajectories that better resemble trajectories from eddy-resolving simulations. Markov-1 also yields a smaller spurious dianeutral flux.

Published
2022

35. Sediment properties in the fluvial and estuarine environments of the Mekong River

Author

Le Hoang-Anh, Gratiot Nicolas, Santini William, Ribolzi Olivier, Soares-Frazao Sandra, and Deleersnijder Eric

Subjects
Environmental sciences, GE1-350
Abstract

The Mekong river, located in Southeast Asia, is one of the largest rivers in the world. It is facing serious problems related to sediment transport, e.g. the reduction of sediment volume supply to the delta and estuary. This study focuses on the physical properties of suspended particles in the upstream fluvial section (Luang Prabang, Laos) and in the region of tidal influence (Song Hau estuary, Vietnam). These sites are respectively the upper and lower limits of the Lower Mekong River (LMR), which are experiencing contrasted transport modes. The main objective of this study is to quantify the proportion of inert sand and of cohesive particles in the water through comprehensive measurements of particle size, settling velocity and flocculation in the water column. Two field campaigns were undertaken in the summer monsoon season. The results point out the predominance of flocculi, with sizes of 18 ± 5 μm in the fluvial environment and 15 ± 5 μm in the estuary and the similarities in patterns, mixture of sand (12 ± 5 %) and mud (88 ± 5 %). They also provide a statistically representative set of suspended particle populations in the upstream and downstream regions that could be used for improving numerical models.

Published
2018
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