Hydrodynamics of Biomimetic Marine Propulsion and Trends in Computational Simulations

[Abstract] The aim of the present paper is to provide the state of the works in the field of hydrodynamics and computational simulations to analyze biomimetic marine propulsors. Over the last years, many researchers postulated that some fish movements are more efficient and maneuverable than traditional rotary propellers, and the most relevant marine propulsors which mimic fishes are shown in the present work. Taking into account the complexity and cost of some experimental setups, numerical models offer an efficient, cheap, and fast alternative tool to analyze biomimetic marine propulsors. Besides, numerical models provide information that cannot be obtained using experimental techniques. Since the literature about trends in computational simulations is still scarce, this paper also recalls the hydrodynamics of the swimming modes occurring in fish and summarizes the more relevant lines of investigation of computational models

Application of the level set method to model the premixed combustion process in an otto two stroke engine

En este artículo se ha utilizado el método numérico conocido como level set para modelar el proceso de combustión en un motor Otto de dos tiempos. Se ha implementado el level set en un software libre de mecánica de fluidos computacional (CFD) basado en volúmenes finitos, el cual ha proporcionado los campos de presión y temperatura, así como la propagación del frente de llama. Con el fin de validar el modelo, los resultados obtenidos numéricamente se han comparado con datos experimentales, obteniendo una concordancia bastante satisfactoria. Asimismo, se ha comparado el método de level set con otro procedimiento numérico muy utilizado, mostrando la diferencia entre ambos resultados.In this paper, the numerical method level set has been used to model the combustion process in an Otto two-stroke engine. The level set has been implemented in a CFD (Computational Fluid Dynamics) software based in finite volumes. The pressure and temperature fields have been obtained, such as the propagation of the flame front. In order to validate this model, the numerically obtained results have been compared with experimental data, verifying a satisfactory concordance between both of them. Besides, the level set method has been compared with other numerical procedure, showing the difference between both results.Peer Reviewe

Analysis of the Pre-Injection System of a Marine Diesel Engine Through Multiple-Criteria Decision-Making and Artificial Neural Networks

[Abstract] The present work proposes several pre-injection patterns to reduce nitrogen oxides in the Wärtsilä 6L 46 marine engine. A numerical model was carried out to characterise the emissions and consumption of the engine. Several pre-injection quantities, durations, and starting instants were analysed. It was found that oxides of nitrogen can be noticeably reduced but at the expense of increasing consumption as well as other emissions such as carbon monoxide and hydrocarbons. According to this, a multiple-criteria decision-making (MCDM) model was established to select the most appropriate parameters. Besides, an artificial neural network (ANN) was developed to complement the results and analyse a huge quantity of alternatives. This hybrid MCDM-ANN methodology proposed in the present work constitutes a useful tool to design new marine engines

Numerical Model of SO2 Scrubbing with Seawater Applied to Marine Engines

[Abstract]: The present paper proposes a CFD model to study sulphur dioxide (SO2) absorption in seawater. The focus is on the treatment of marine diesel engine exhaust gas. Both seawater and distilled water were compared to analyze the effect of seawater alkalinity. The results indicate that seawater is more appropriate than distilled water due to its alkalinity, obtaining almost 100% cleaning efficiency for the conditions analyzed. This SO2 reduction meets the limits of SOx emission control areas (SECA) when operating on heavy fuel oil. These numerical simulations were satisfactory validated with experimental tests. Such data are essential in designing seawater scrubbers and judging the operating cost of seawater scrubbing compared to alternative fuels

Numerical Analysis of NOₓ Reduction Using Ammonia Injection and Comparison With Water Injection

[Abstract] This work analyzes NOₓ reduction in a marine diesel engine using ammonia injection directly into the cylinder and compares this procedure with water injection. A numerical model based on the so-called inert species method was applied. It was verified that ammonia injection can provide almost 80% NOₓ reduction for the conditions analyzed. Furthermore, it was found that the effectiveness of the chemical effect using ammonia is extremely dependent on the injection timing. The optimum NOₓ reduction was obtained when ammonia is injected during the expansion stroke, while the optimum injection timing using water is near top dead center. Chemical, thermal, and dilution effects of both ammonia and water injection were compared. The chemical effect was dominant in the case of ammonia injection. On the other hand, water injection reduces NOₓ through dilution and, more significantly, through a thermal effect

Heterogeneous catalysis for the synthesis of carbon dots (CDs) from biomass source

It has been evaluated the capacity of several phosphate-based acid catalysts of transition metals such as vanadium and niobium in the synthesis of carbon dots (CDs) via a hydrothermal process. For this purpose, two sources of carbohydrates have been used: commercial xylose and liqueur of xylose obtained from the treatment of olive pits. Catalysts were characterized by means of NH3-TPD, DTA/TG, XRD and XPS. The reaction was carried out at 180 °C and reaction time was varied between 2 and 4h. The properties and characteristics of CDs nanoparticles were analysed confirming the existence of such nanoparticles irrespective the carbohydrate source. In terms of CDs quality, both syntheses produced comparable results. At the same time, N doped CDs with enhanced fluorescence were also synthesized following a kindred hydrothermal process and the photocatalytic activity was studied. With the aim of evaluating the environmental impact of the synthesis from commercial xylose versus the synthesis from biomass, a Life Cycle Assessment (LCA) analysis was carried out for both syntheses. It showed that the most sustainable synthesis route is the one that uses commercial xylose as carbonaceous feedstock. Furthermore, while electricity is the main contributor to all impact categories in both synthesis routes, the main differences that determine their relative sustainability are associated with the identity of the carbon precursor.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

For an environmental ethnography in human and physical geography : re-envisioning the impacts and opportunities of El Niño in Peru

Funding: This work was supported by the Royal Society under Grant RG120575; the Natural and Environmental Research Council under Grant NE/R004528/1; the Scottish Funding Council under Grant SGS0-XFC090; and The Arts and Humanities Research Council under Grant AH/T004444/1AH.In 2017 El Niño Costero devastated the northern coast of Peru. This article seeks to learn from this experience for future large central and eastern Pacific-driven El Niño events. It directs attention away from dominant disaster narratives to reflect on the opportunities that El Niño rains have generated for desert livelihoods over time. We make a call for and set out the key elements of a historical geographical ethnography approach in environmental geography, which, as well as examining climate dimensions (paleoclimatology, dendrochronological, and atmospheric changes) of El Niño, also aims to consider its impacts on the livelihoods and management strategies of desert communities over time. We take as a starting point the responses of people who themselves come directly into contact with environmental change, yet whose agency and experiences are often marginal in knowledge production about El Niño. Responding to recent calls for qualitative geography researchers to be more explicit about how data are collected and analyzed, we explain how and why it is important to compare stakeholder interviews and climate records with newspaper archives and community memories of the 1983 and 1998 El Niño events. We illustrate that for desert populations in northern Peru, El Niño can represent abundance as well as disaster and make visible their role in managing change after El Niño flooding.Peer reviewe

Commented checklist of marine fishes from the Galicia Bank seamount (NW Spain)

A commented checklist containing 139 species of marine fishes recorded at the Galician Bank seamount is presented. The list is based on nine prospecting and research surveys carried out from 1980 to 2011 with different fishing gears. The ichthyofauna list is diversified in 2 superclasses, 3 classes, 20 orders, 62 families and 113 genera. The largest family is Macrouridae, with 9 species, followed by Moridae, Stomiidae and Sternoptychidae with 7 species each. The trachichthyd Hoplostethus mediterraneus and the morid Lepidion lepidion were the most abundant species. Biogeographically, the Atlantic group, with 113 species (81.3%) is the best represented, followed by the Lusitanian one with 17 species (12.2%). Data on species abundance, as number of individuals caught, size and depth are reported. Habitat, distribution and vulnerability status are commented. Moreover, biometric data and meristic counts are also reported for several species. The results obtained showing a high fish biodiversity and a sensible number of threatened species, strongly support the future declaration of the Galicia Bank as a Marine Protected Area.En prensa0,974