Projecte llegit
Títol: Modelling the exchange of small plastics between the inner surf zone and the open sea under different beach configurations
Estudiants que han llegit aquest projecte:
- BALBOA MATO, DAVID (data lectura: 30-11-2020)
- Cerca aquest projecte a Bibliotècnica
Director/a: RIBAS PRATS, FRANCESCA
Departament: FIS
Títol: Modelling the exchange of small plastics between the inner surf zone and the open sea under different beach configurations
Data inici oferta: 01-11-2019 Data finalització oferta: 31-05-2020
Estudis d'assignació del projecte:
- GR ENG SIST AEROESP
Tipus: Individual | |
Lloc de realització: EETAC | |
Nom del segon director/a (UPC): Albert Falqués Serra | |
Departament 2n director/a: | |
Paraules clau: | |
Fluid mechanics, Numerical methods, Marine plastic debris | |
Descripció del contingut i pla d'activitats: | |
The leakage of plastic debris
into the ocean is a major environmental problem because the amount of plastic in the marine ecosystems is exponentially growing and it could become dangerous for animals and people (Koelmans et al., 2017). However, the present understanding of the marine plastic budget and of plastic motion through the ocean is inadequate, prompting the EU to make this issue a top science priority and funding research projects like TOPIOS (http://topios.org/). About 60% of the plastic emitted to the ocean initially floats (it has a density lower than sea water). Also, plastic size is variable and it is classified as macroplastic (d > 5 mm), microplastic (5 mm > d > 0.335 mm) and nanoplastic (d < 0.335 mm) (Koelmans et al., 2017). One of the present open problems is the exchange of plastic between land and ocean through sandy coasts, which are about 25% of the coasts on a global scale. The swash and surf zones of sandy beaches, where breaking waves, currents and sediment interact in a complex nonlinear way, are highly variable and its internal dynamics can strongly affect the motion of plastics (Castelle and Coco, 2013). This internal dynamics include the common formation of alongshore- rhythmic sandy patterns like mega-cusps, transverse bars and crescentic bars (Garnier, 2006), which are coupled to the presence of seaward directed rip-currents that can enhance the flushing of floating material towards the ocean (Castelle and Coco, 2013). The focus of this study is to quantify how the morphological beach configuration affects the exchange of small plastics between the swash zone and the open sea. For this, an existing nonlinear model called morfo55, which describes the dynamics of waves, currents, sediment and sea bed level (Garnier, 2006), will be run to create several study cases with different beach conditions. Using the wave and water velocity fields obtained with morfo55, an advection/diffusion equation for the concentration of plastics will be applied to quantify its evolution. Planned activities: Task 1: Get acquainted with: i) the problem of marine plastic debris, ii) the fundamentals of beach morphodynamics and morfo55 model, iii) numerical methods based on finite differences. About 2 weeks. Task 2: Construct a Matlab code that solves numerically the advection/diffusion equation for the plastic concentration and test it against an analytical case. About 2 weeks. Task 3: Use the Morfo 55 code to generate the steady wave and water velocity fields for different study cases: e.g., with a shore-parallel bar (and different wave height, period and angle) and with a crescentic bar (and different wave height, period and angle). About 4 weeks. Task 4: Read the steady wave and velocity field of morfo55 in the Matlab code and solve the concentration equation for the different study cases. Quantify the exchange of plastic between the swash zone and the open sea. About 6 weeks. Task 5: Introduce the advection/diffusion equation for the concentration in Morfo55 and solve it under unsteady conditions (for example, under the occurrence of shear instabilities of the longshore current). About 6 weeks. Task 6: Write the TFG thesis. About 3 weeks. References: Castelle, B., and Coco, G. (2013). Surf zone flushing on embayed beaches, Geophys. Res. Lett., vol. 40, 2206-2210, doi:10.1002/grl.50485. Garnier, R. (2006). Nonlinear modelling of surf zone morphodynamical instabilities, PhD thesis, ed. by Universitat Politecnica de Catalunya, December 2006. Koelmans, A.A., Kooi, M., Lavender Law, K., and van Sebille, E. (2017). All is not lost: deriving a top-down mass budget of plastic at sea, Environ. Res. Lett., vol. 12, 114028, doi: https://doi.org/10.1088/1748- 9326/aa9500 |
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Overview (resum en anglès): | |
This document shows the procedure carried out to model the Exchange of small plastics between the inland surfing area and the open sea under different beach configurations. The damage caused by plastics to the ocean and the fauna it has contained for years is an emerging and increasingly studied problem. To fully understand the dynamics that a plastic can have on the surface of the water you must know the morphodynamics of the beaches, where many events occur simultaneously at different scales that continuously deform the beach, is a complex and difficult to predict place. Using a model called MORFO55 developed by the Group of Nonlinear Fluid Dynamics of the UPC we managed to obtain reliable data from this morphodynamics and with this data and using Matlab software we developed an algorithm capable of showing the dynamics of a plastic under different configurations. The main objective of this project is to observe how the formation of a rhythmic sand pattern along the coast called crescent bar or crescent bar influences and therefore the formation of a system of deep currents influences the dynamics. of these plastics on the surface of the water.
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