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Three-dimensional cfd analysis to study the thrust and efficiency of a biologically-inspired marine propulsor

Three-dimensional cfd analysis to study the thrust and efficiency of a biologically-inspired marine propulsor

Aquatic animals, which are the result of many millions of years of evolutionary optimization, are very quick, efficient, robust, and versatile. Accordingly, biologically-inspired mechanisms which emulate the movement of animals have recently become very popular. For the efficient design of a propulsion system it is very important to analyze the fluid flow in detail. CFD (Computational Fluid Dynamics) has become a powerful technique to understand the phenomena because it gives extensive information about the fluid flow characteristics.

In the present work, a propulsion system consisting of an undulating fin which emulates the fish swimming was built. In order to optimize the mechanism, several undulating configurations were studied using a 3D turbulent CFD model. The thrust, drag, efficiency and hydrodynamic characteristics were analyzed. Furthermore, it was shown that the efficiency and thrust depend strongly on the oscillation frequency, amplitude and wavelength.

In order to validate this CFD model, the numerically obtained thrust was successfully compared with experimental results from the laboratory mechanism.

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Effect of hydraulic loading rate and vegetation on phytoremediation with artificial wetlands associated to natural swimming pools

Abstract

The treatment of pool water, whether for recreational or sporting purposes, by phytoremediation is widely applied. This work evaluates two artificial vertical flow wetlands, one on a real scale and the other on a laboratory scale, which have been planted with Typha domingensis, for the treatment of pool water in the climatic conditions of the city of Santiago de Cuba. When the hydraulic load applied to the real scale wetland was less than 0.25 m3∙m–2∙d–1, the levels of organic and microbiological contamination in the pool were below the maximum limits allowed by Cuban standards. At a laboratory scale, the presence of vegetation favoured the elimination of nitrogen compounds (nitrates and ammonium) and organic materials (BOD and COD). This behaviour is explained by the presence of processes of assimilation of organic compounds, or by the action of microorganisms associated with the rhizome of plants, which establish a symbiotic mechanism favourable to phytodepuration. The minimum concentration of ammonium obtained in outflow from the laboratory-scale reactor without vegetation reached a value of 2.15 mg∙m–3, which is within the limits allowed by the sanitary regulations.

Open access