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This study numerically analyzes a submerged horizontal plate (SHP) device subjected to both regular and irregular waves. This device can be used either as a breakwater or a wave energy converter (WEC). The WaveMIMO methodology was applied for the numerical generation and wave propagation of the sea state of the Rio Grande coast in southern Brazil. The finite volume method was employed to solve conservation equations for mass, momentum, and volume fraction transport. The volume of fluid model was employed to handle the water-air mixture. The SHP length (Lp) effects were carried out in five cases. Results indicate that relying solely on regular waves in numerical studies is insufficient for accurately determining the real hydrodynamic behavior. The efficiency of the SHP as a breakwater and WEC varied depending on the wave approach. Specifically, the SHP demonstrates its highest breakwater efficiency in reducing wave height at 2.5Lp for regular waves and 3Lp for irregular waves. As a WEC, it achieves its highest axial velocity at 3Lp for regular waves and 2Lp for irregular waves. Since the literature lacks studies on SHP devices under the incidence of realistic irregular waves, this study significantly contributes to the state of the art. [ABSTRACT FROM AUTHOR]

This research conducts a numerical study of a wave energy converter (WEC) device with five coupled hydropneumatic chambers, operating based on the principle of an oscillating water column (OWC). A turbine was not included, only considering the tube without it. The computational domain was defined by a wave channel housing an OWC device subjected to regular incident waves. The central objective was to assess the impact of chamber geometry on maximizing the total hydropneumatic power in energy conversion. The numerical simulations consider the pressure, mass flow rate, and total hydropneumatic power, with the latter being the performance indicator. To determine the geometries to be analyzed, the Constructal Design method was employed in conjunction with the exhaustive search optimization method to maximize the performance indicator. The degrees of freedom defined were the ratios between the height (Hn) and the length (Ln) of the hydropneumatic chambers (Hn/Ln, where n varies from one to five). Based on the results of the mass flow rate and pressure, their influence on power was evaluated. It was observed that the influence of the degrees of freedom on the pressure difference, mass flow rate, and hydrodynamic power was quite similar, displaying an increase for low ratios of Hn/Ln up to a maximum magnitude and followed by a decrease in magnitude. The best performance was achieved for the geometric configuration with Hn/Ln = 0.2613 (Hn = 5.0625 m and Ln = 15.8219 m), representing an improvement of 98.6% compared to the worst case analyzed. [ABSTRACT FROM AUTHOR]

The high availability of energy within ocean waves is seen as an important and abundant alternative as a renewable energy source. This paper presents a numerical study of the submerged horizontal plate type wave energy converter, assessing its theoretical efficiency for several relative plate heights. The propagation and incidence of distinct wave periods through the device structure were simulated, and the device efficiency was evaluated disregarding the presence of the turbine under the plate. A total of six wave periods between 1.25 and 3.50 s with wave height of 0.06 m were considered for six different plate heights. The results allow to make theoretical recommendations on the converter performance. The multiphase Volume of Fluid model was used through a two-dimensional approach for air-water interaction and the conservation equations of mass, momentum and volume fraction transport were solved by the Finite Volume Method. The results of analysis allowed to observe that the highest relative plate height leads to enhanced submerged horizontal plate efficiencies among the simulated wave periods, as well as to identification of a theoretical device efficiency up to three times higher for larger wave periods than for shorter wave periods.

In the naval industry, hydrofoils are used for generating lift in low-friction vessels, minimizing drag forces between the surrounding fluid and the hull. These devices are also applied to keep stability and maneuverability for high-speed vessels. A recent technology based on Coanda effect for flows over hydrodynamic profiles has been developed for the application of this equipment to increase the flow, converting lifting forces into propelling ones, aiming to attend the industry interest for developing improved nautical propulsion mechanisms. The main purpose of the present work is to simulate the main operational principle of a hydro-propulsion device based on the Coanda effect. More precisely, a turbulent water flow in two hydrodynamic profiles is considered. The mass flow rate of water in the device is thoroughly studied in this work, solving numerically time-averaged conservation equations of mass and momentum with Computational Fluid Dynamics (CFD) code based on the Finite Volume Method (FVM). To tackle with closure modeling for turbulence it is employed the standard k - ε model. The effect of distance between two hydrodynamic profiles over the mass flow rate is also studied. Results obtained here show that the multiplying effect is noticed in water flow in the region between two hydrodynamic profiles, which is similar to previous findings of the literature for the air flow through aerodynamic profiles submitted to Coanda effect.

Given the increasing global energy demand, the present study aimed to analyze the influence of bathymetry on the generation and propagation of realistic irregular waves and to geometrically optimize a wave energy converter (WEC) device of the oscillating water column (OWC) type. In essence, the OWC WEC can be defined as a partially submerged structure that is open to the sea below the free water surface (hydropneumatic chamber) and connected to a duct that is open to the atmosphere (in which the turbine is installed); its operational principle is based on the compression and decompression of air inside the hydropneumatic chamber due to incident waves, which causes an alternating air flow that drives the turbine and enables electricity generation. The computational fluid dynamics software package Fluent was used to numerically reproduce the OWC WEC according to its operational principles, with a simplification that allowed its available power to be determined, i.e., without considering the turbine. The volume of fluid (VOF) multiphase model was employed to treat the interface between the phases. The WaveMIMO methodology was used to generate realistic irregular waves mimicking those that occur on the coast of Tramandaí, Rio Grande do Sul, Brazil. The constructal design method, along with an exhaustive search technique, was employed. The degree of freedom H1/L (the ratio between the height and length of the hydropneumatic chamber of the OWC) was varied to maximize the available power in the device. The results showed that realistic irregular waves were adequately generated within both wave channels, with and without bathymetry, and that wave propagation in both computational domains was not significantly influenced by the wave channel bathymetry. Regarding the geometric evaluation, the optimal geometry found, (H1 / L)0 = 0.1985, which maximized the available hydropneumatic power, i.e., the one that yielded a power of 25.44 W, was 2.28 times more efficient than the worst case found, which had H1/L = 2.2789. [ABSTRACT FROM AUTHOR]

This work shows an analysis of the construction of the geometric arrangement of blocks mounted on the surfaces of a channel subjected to a laminar, incompressible flow, with forced convection in a two-dimensional domain. The construction is carried out using a construction function based on the system's performance indicator, i.e., the heat transfer rate from the arrangement to the fluid flow. For the assembly of the arrangement, a methodology based on the principles of the Constructal Theory is employed. To solve the convection problem, the conservation equations for mass, momentum, and energy are solved using the Finite Volume Method, more precisely using the FLUENT software. The objective of this work is to understand how the construction of the initial blocks of the array (N = 3 blocks) occurs in an area occupied by the channel in flows with forced convection and Reynolds and Prandtl numbers of ReH = 100 and Pr = 0.71. The best and worst cases for N = 2 led to an increase of 93.21% and 28.59%, respectively, compared to the N = 1 case. The results demonstrated that the construction leading to the best thermal performance is the configuration where there is the highest momentum between the blocks (enhancing the convective heat transfer coefficient) and the lowest interaction between the thermal boundary layers, which is in agreement with the principle of optimal distribution of imperfections. [ABSTRACT FROM AUTHOR]

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Copyright of Revista Ciência e Natura is the property of Revista Ciencia e Natura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Ciência e Natura is the property of Revista Ciencia e Natura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Ciência e Natura is the property of Revista Ciencia e Natura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)