Controlling eutrophication by means of water recirculation: an optimal control perspective

In this work, the artificial recirculation of water is presented and analyzed, from the perspective of the optimal control of partial differential equations, as a tool to prevent eutrophication effects in large waterbodies. A novel formulation of the environmental problem, based on the coupling of nonlinear models for hydrodynamics, water temperature and concentrations of the different species involved in the eutrophication processes, is introduced. After a complete and rigorous analysis of the existence of optimal solutions, a full numerical algorithm for their computation is proposed. Finally, some numerical results for a realistic scenario are shown, in order to prove the efficiency of our approach.Xunta de Galicia | Ref. ED431C 2019/02Agencia Estatal de Investigación | Ref. MTM2016-75140-

On existence and uniqueness of solution for a hydrodynamic problem related to water artificial circulation in a lake

In this work we introduce a well-posed mathematical model for the processes involved in the artificial circulation of water, in order to avoid eutrophication phenomena, for instance, in a lake. This novel and general formulation is based on the modified Navier–Stokes equations following the Smagorinsky model of turbulence, and presenting a suitable nonhomogeneous Dirichlet boundary condition. For the analytical study of the problem, we prove several theoretical results related to existence, uniqueness and smoothness for the solution of this recirculation model.Xunta de Galicia | Ref. ED431C 2018/50Ministerio de Economía y Competitividad | Ref. MTM2015-65570-

Mathematical analysis and numerical resolution of a heat transfer problem arising in water recirculation

This work is devoted to the analysis and resolution of a well-posed mathematical model for several processes involved in the artificial circulation of water in a large waterbody. This novel formulation couples the convective heat transfer equation with the modified Navier–Stokes system following a Smagorinsky turbulence model, completed with a suitable set of mixed, nonhomogeneous boundary conditions of diffusive, convective and radiative type. We prove several theoretical results related to existence of solution, and propose a full algorithm for its computation, illustrated with some realistic numerical examples.Ministerio de Economía y Competitividad | Ref. MTM2015-65570-PXunta de Galicia | Ref. ED431D 2017/1

A computational framework for informing decision in relation to environmental impact of wastewater discharges

Multi-objective optimization combined with numerical simulation are useful tools for environmental sciences. Using these methods, the treatment and discharge of wastewater in large waterbodies (estuaries, rivers, lakes. . . ) - one of the essential problems in environmental management - can be analyzed in order to avoid the usual controversy between economic and ecological interests. In this article we present a decision support software system referred to as Simulating Optimal Solutions (SOS). Software SOS is a Matlab toolbox (interfaced with Fortran codes for mathematical computation of hydro- dynamics and contaminant dispersion) to assess in decision making related to treatment intensity in different purifying plants. The program allows a flexible analysis both from a cooperative viewpoint (Pareto optimality) and a non-cooperative one (Nash equilibria). A realistic example posed in Arousa estuary (NW Spain) helps us to show its capabilities

Algal cultivation for bioenergy production: first mathematical modelling results in raceways

The most used algae cultivation systems are the open-channel raceway ponds for their low maintenance and energy costs. Raceways allow algal cultivation using wastewater, where algae mass can be employed as source for bioenergy production. One of the main external factors influencing algal productivity is the velocity of the liquid inside the pond, that can be easily controlled by the position and/or rotational speed of the turning paddle wheel, and by the height of water. In this work we introduce a novel methodology to automate the optimization of the design of raceway ponds based on techniques of optimal control of partial differential equations. So, we formulate the problem as a control problem where the state system is given by the coupled nonlinear equations for hydrodynamics and algae/nitrogen/phosphorus concentrations, and the objective function to be maximized represents the global concentration of algae at final time. We present here a detailed, rigorous mathematical formulation of the optimal control problem, we propose a numerical algorithm for its resolution, and we show some preliminary computational results related to the numerical modelling of the problem

Research patterns in communication (2009-2019): testing female representation and productivity differences, within the most cited authors and the field

This study compares the share of male/female as first authors, the growth of authors per paper, and the differences in publication productivity in the last decade of the most cited authors versus the field of communication (i.e., a representative sample of papers published in the field of communication). Results indicate that there are significantly more female first authors in the field than a decade ago, but their proportion among the most cited authors has not grown at a similar pace. Likewise, the number of authors per paper has significantly increased in the field, but not among the most cited authors, who, in turn, publish significantly more papers than the field, both in 2009 and 2019. And not only that, the productivity gap between the most cited authors and the field has substantially increased between the span of this decade. Theoretical implications of these findings and suggestions for future studies are also discussed.A prior version of this article was sent to 2021 AEJMC Conference. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. No funding was received for conducting this study

Optimizing the design of an estuarine water quality monitoring network by optimal control techniques

In this work, we propose a novel methodology in order to automatically optimize the location of the sampling points for a water quality monitoring network in an estuary, in such a way that any unknown pollution source can be identified (both in intensity and location) from the data supplied by those sampling points. In the central part of the article, after a rigorous mathematical formulation of the environmental problem, the full details of its numerical implementation are given. Finally, we present and analyze the results when applying the above proposed technique to study a real case in Ría of Vigo (northwestern Spain).Agencia Estatal de Investigación | Ref. TED2021-129324B-I00Universidade de Vigo/CISU