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Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy converter (OWC-WEC). This study shows a numerical analysis of the diameter determination of two types of turbines, Wells and Impulse, installed in an onshore OWC device subjected to a hypothetical sea state. Commercial software FLUENT®, which is based on RANS-VoF (Reynolds-Averaged Navier-Stokes equations and Volume of Fluid technique), is employed. A methodology that imposes air pressure on the chamber, considering the air compressibility effect, is used. The mathematical domain consists of a 10 m deep flume with a 10 m long and 10 m wide OWC chamber at its end (geometry is similar to that of the Pico’s plant installed in Azores islands, Portugal). On the top of the chamber, a turbine works with air exhalation and inhalation induced by the water free surface which oscillates due to the incident wave. The hypothetical sea state, represented by a group of regular waves with periods from 6 to 12 s and heights from 1.00 to 2.00 m (each wave with an occurrence frequency), is considered to show the potential of the presented methodology. Maximum efficiency (relation between the average output and incident wave powers) of 46% was obtained by using a Wells turbine with the diameter of 2.25 m, whereas the efficiency was 44% by an Impulse turbine with the diameter of 1.70 m.

The most studied device used for extracting wave energy is the Oscillating Water Column (OWC). In general, numerical simulations of these cases by means of models based on Reynolds Averaged Navier-Stokes equations adopt the Volume of Fluid method to deal with the free surface flow which is considered incompressible in both water and air. The aim of this study is to investigate the influence of the compressibility effect on the air inside the OWC chamber by the FLUENT® numerical model. A methodology is implemented, taking into account both water and air flows incompressible, but, at every instant, a pressure condition is imposed on the top boundary of the chamber to consider the compressibility effect. This pressure condition is based on an analytical equation that considers the isentropic transformation of the air and effects of Wells and impulse turbines. Results of compressible and incompressible numerical models are compared. The amplification factor, the root mean square of air pressure inside the chamber and OWC efficiency in relation to incident wave period, wave height and turbine characteristic relation are analyzed. Results show that air compressibility effects can diminish the predicted OWC efficiency up to about 20% in both Wells and impulse turbines.

Knowledge of forces due to the action of waves on submarine outfalls composed by a pipe and stabilizing concrete weights, considering the wave propagation direction to the outfalls, is essential to their design. 3D numerical models based on RANS-VoF (Reynolds-Average-Navier-Stokes Volume-of-Fluid) are able to estimate forces on the pipe and weights. The present study aims to simulate a submarine outfall with stabilizing concrete weights at 1:15 scale which was previously tested in the 3D Shallow Water Basin at the Danish Hydraulics Institute (DHI) to analyse the influence of the direction of the incident wave and the distance from the pipe to the bottom on the outfall forces. In this study, numerical results are compared with experimental ones for waves with four different amplitudes and with wave incidence perpendicular to the outfall. The use of k-ω SST turbulence model led to good agreement between numerical drag and lift forces and experimental ones, with a mean difference of 8.9 and 7.6%, respectively.

Although studies show high wave energy potential in several coastal regions around the world, its evaluation and detailed characterization are necessary to optimize its harvest. This study aims at numerically evaluating the power output of an Oscillating Water Column (OWC) wave energy converter installed in the southern Brazilian coast. The FLUENT® numerical model, based on the Reynolds Averaged Navier-Stokes (RANS) equations and the Volume of Fluid (VoF) technique, is used. The turbine diameter optimization (TDO) model, which considers the motion of the water surface inside the OWC chamber as a piston movement in response to the hydrodynamic forces from the incoming waves, is also employed. The OWC is equipped with a Wells turbine, with pressure control (relief valve) and regulation of the turbine rotational speed. The turbine diameter is chosen by taking into account the wave characteristics in the region where the device is installed. An OWC device 10 m wide, 10 m long, 16 m high (10 m submerged) with a front wall 2.5 m submerged reaches its optimum performance with an annual-averaged power output of 36.48 kW (efficiency of 54.6%), by using a turbine with 2.25 m diameter.

This paper describes a methodology to determine the optimal size of a Wells turbine to be used in an OWC device taking into account hydro-aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The proposed model, named turbine diameter optimization (TDO) model, considers the movement of the water surface inside the OWC chamber as a piston movement in response to the hydrodynamic forces from the incoming waves. The aerodynamic is based on the first law of thermodynamics applied to the air column of the chamber. The power-pressure curve of the turbine and the air pressure control by relief valve are implemented in the model to determine the turbine power output for several regular incident waves. The TDO model is initially calibrated by a numerical model based on Reynolds-Average-Navier-Stokes (RANS) equations for each wave component of an expected sea state distribution. Thereafter, the power output generated by turbines of several sizes is calculated with lower computational cost (few minutes) in comparison with RANS based models (thousands of hours) in a personal computer. This developed methodology is an important support to the process of turbine sizing for an OWC device for an expected sea state distribution.

This paper describes the preliminary developments of an innovative integrated tool for the numerical modelling of oscillating water column (OWC) wave energy converters (WEC) integrated in vertical breakwaters. The main purpose of the tool is the numerical modelling of wave propagation from offshore to nearshore, wave-structure interaction, and the complex nonlinear hydrodynamic and aerodynamic phenomena that occur in OWC-WECs. The tool development and validation were supported by experimental data from physical model tests carried out in a wave flume at the Portuguese National Laboratory for Civil Engineering (LNEC). Prototype data were also available for the Pico OWC-WEC in the Azores, Portugal, monitored by the Portuguese Wave Energy Centre since 2005. Application of the tool for sea-wave characterization at the Azores archipelago and calculation of the corresponding wave power for a period of 10 years at various points around each island show that, in winter, there is good availability of wave energy in most quadrants of each island. In summer, the resource exploitation is only worthwhile on the north-west coasts of the islands. Physical and numerical modelling results for an OWC with a fully open chamber show good agreement between experimental data and numerical values for several incident wave conditions. The analysed results include the time series of the free-surface elevation at different locations, the time series of the mean free surface inside the water chamber, the amplification factors, the phase angles and the velocity vectors at the highest and the lowest positions of the mean free surface inside the chamber. The tool showed its potential to be useful in supporting ocean and coastal engineering projects due to its capacity to effectively reproduce the main phenomena involved in these types of studies.

This paper presents the validation of active and passive, made by a dissipation beach, numerical absorbing methods implemented in RANS-VOF FLUENT® code for modelling long time series of wave propagation interacting with coastal structures. Verification of both numerical techniques was performed in 2D – wave flume, and 3D – wave tank, this one using a multiple active absorption wave makers. The active absorption wave maker allows maintaining the incident wave generation and the mean water level along the time. Good results were obtained for 2D and 3D applications for active absorption wave maker at the generation boundary and both numerical beach and active absorption at the end of the flume/tank.

This paper describes the analysis of the propagation of regular and irregular waves in a flume by using Fluent® model, which is based on the Navier-Stokes (NS) equations and employs the finite volume method and the Volume of Fluid (VoF) technique to deal with two-phase flows (air and water). At the end of the flume, a numerical beach is used to suppress wave reflections. The methodology consists of adding a damping sink term to the momentum equation. In this study, this term is calibrated for three cases of regular incident waves (H = 1 m, T = 5, 7.5, and 12 s) by varying the linear and quadratic damping coefficients of the formulation. In general, while lower values of damping coefficients cause residuals on the free surface elevation due to wave interactions with the outlet boundary, reflection occurs on the numerical beach when higher values are used. A range of optimal damping coefficients are found considering one of them null. In one of these cases, temporal series of free surface elevation are compared with theoretical ones and very good agreement is reached. Afterwards, an irregular wave propagation, characterized by a JONSWAP spectrum, is investigated. Several gauges along the flume are evaluated and good agreement between the spectrum obtained numerically and the ones imposed at beginning of the flume is verified. This study shows the capacity of NS models, such as Fluent®, to simulate adequately regular and irregular wave propagations in a flume with numerical beach to avoid reflections.

Wave energy extraction in coastal regions may be an excellent alternative due to the increase in global demand for renewable energy. The viability study of this extraction depends on the evaluation of the wave energy potential that is higher in regions located in high latitudes. Therefore, this study shows evaluation and characterization of wave energy in the south of Brazil. Numerical simulations were carried out by the Mike 21 SW spectral model which was calibrated and validated in the region measurement campaigns. Annual, seasonal and monthly means and the temporal variability of the wave energy potential in a 10-year wave hindcast were analyzed offshore and nearshore. Annual mean fluxes in three points nearshore had similar values; the highest one was 6.7 kW/m, while the wave energy flux offshore was 22.3 kW/m. The refraction and the bottom friction dissipation were responsible for the wave attenuation from offshore to nearshore and, consequently, for the decrease in wave energy. The annual, seasonal and monthly variabilities of wave energy fluxes were moderate offshore and high nearshore. A directional analysis showed that the dominant wave directions were S and NE offshore whereas they were SSE and E nearshore.

Fluid-dynamic interference among cylindrical structures in arrays, frequently used in engineering, is of fundamental and practical interests since it may considerably change fluid–structure interactions and produce large fluctuating forces on structures that cause vibrations, lock-in and important motions. This paper aims to study the mutual interference between two circular cylinders in tandem arrangement, which is considered the simplest configuration of one array cylinders, elastically mounted in transversal direction and subject to a bi-dimensional uniform laminar flow at low Reynolds numbers. Both cylinders have the same diameter D, and the center-to-center spacing is equal to L = 5.25D which corresponds to co-shedding regime. The academic numerical model Ifeinco, which is based on the finite element method and uses a partitioned scheme that considers two-way interaction of fluid flow and structure, has been employed to the analysis. Combinations of upstream and downstream stationary and elastically mounted cylinders are investigated for Reynolds number range from 90 to 140. Differences of flow behaviors drag and lift forces and resonance between single cylinder and cylinders in tandem arrangement were found. Mutual and respective influences of upstream cylinder motion on the downstream cylinder and vice versa are analyzed. Results show that, in some engineering studies, the consideration of the flexibility of cylindrical structures in arrays is fundamental since it influences significantly the interference between cylinders, mainly the magnitude and direction of forces and characteristics of the resonance range, and, consequently, structural and dynamical behaviors.

The main objective of this study is to investigate differences of random incident waves from regular ones in performance of wave energy converters (WEC). A numerical analysis of an onshore oscillating water column (OWC) WEC is carried out by means of the FLUENT® software, which is based on Reynolds-Averaged Navier-Stokes equations. Analyses of the efficiency of an onshore OWC device with similar characteristics of the Pico’s plant and equipped with a Wells-type turbine, located at a 10 m deep flume, subjected to random waves with TMA spectrum and regular waves are shown. The resonance occurs at an energy period T = 8.6 s with an efficiency of 62% for a root mean square wave height Hrms = 1 m in random waves, while it is observed at T = 7.1 s with 84% of efficiency for H = 1.00 m in regular waves. Differences between efficiencies of regular and random waves are significant up to around the resonant period. This study showed that the use of random incident waves is fundamental to obtain more real results of analyses of onshore OWC device performance, even considering their requirement of high simulation time.

Despite the simplicity of the geometry of the circular cylinders, the uniform flow around them is complex, since it may induce unsteady forces on structures associated with vortex shedding. This paper describes the study of two circular cylinders (the downstream one is elastically mounted in transversal direction) in tandem arrangement subject to bi-dimensional uniform laminar flows at low Reynolds numbers. The academic numerical model Ifeinco, which is based on the finite element method and uses a partitioned scheme that considers two-way interaction of fluid flow and structure, has been employed to the analysis. Firstly, both stationary cylinders in tandem arrangement for Re = 100 are analysed for center to center distance between the cylinders, L/D, from 1.5 to 6.0. Results of lift and drag coefficients and Strouhal number are compared with other numerical results and good agreement is found. Secondly, numerical results for L/D = 5.25, considering downstream elastically mounted cylinder, are analysed for Reynolds numbers ranging from 100 to 140. It shows that the resonance occurs for Reynolds numbers between 115 and 120 and the maximum dimensionless amplitude of oscillation is 0.721 for Re = 118.

The availability of clean energy of wind waves is enough to meet current demand of the world, attracting researches to find devices with good performance to extract this type of energy. The oscillating water column converter is a type of device that has been extensively studied for this purpose. This paper describes a numerical analysis of an onshore oscillating water column device taking into account hydrodynamic and aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The numerical analyses are carried out by the Fluinco model, based on slightly compressible flow method to solve the Navier–Stokes equations, and employing the two-step semi-implicit Taylor–Galerkin method. The aerodynamic model is based on the first law of thermodynamics applied to the air column inside the chamber and on turbines similar to Pico's. The turbine power output with air pressure control inside the chamber due to a relief valve is compared to the one without control. A significant increase in the power output by using the pressure control in comparison with that without control is observed. The analysis of the turbine power output considers different turbine diameters and ranges of rotational speeds.

This paper presents the application and the validation of the SPH numerical model SPHyCE, based on a standard Smoothed Particle Hydrodynamics formulation, for modeling an onshore oscillating water chamber, comparing results of amplification factor and phase lag with those obtained by a mesh-based RANS model. Firstly, an analysis of the results for different resolutions (i.e. particle dimension) showed the independence of results with refinement. Secondly, the amplification factor of mean free surface elevation inside the oscillating water chamber and the phase lag between time series of free surface elevation outside and inside the water chamber were analysed. A good agreement was achieved between the mesh free SPHyCE model and the mesh-based RANS model. SPHyCE model was finally applied to analyse the hydrodynamic fluid flow inside and outside the water chamber and to quantify the forces on the vertical wall and the amplification factor for different incident wave heights for a rough sea state with complex wave breaking, impact loads and overtopping, contributing to the future applications of SPH models for development and studies of OWC devices.

Welding processes on plates involve complex physical and chemical phenomena which make mathematical modeling difficult. Although coupled thermal-mechanical-metallurgical effects are important, good results can usually be found when numerical models based on heat transfer equation and governing equations of the structural behavior are used. In this paper, a numerical analysis of multi-pass single V-groove weld in butt joint (three passes) of AISI 304L stainless steel, using the conventional MIG/MAG process is presented. The plates are 9.6 mm thick, 200 mm long and 50 mm wide. The numerical simulations were performed by ANSYS® Multiphysics software, considering a moving heat source with Gaussian type distribution, convection and radiation heat transfer on the surfaces and temperature-dependent material properties, for both mechanical and thermal simulations. The von Mises yield criterion and associated flow rule are used together with kinematic hardening and a bilinear representation of the stress–strain curve. The element birth and death technique is employed to consider an appropriate analysis of the welding processes with material deposition. The fusion zone shape, thermal cycles and final distortion of the plates obtained from the experiments developed in the laboratory of research in welding engineering (LAPES–FURG), located in Rio Grande, RS, Brazil, are compared with numerical results. In general, both thermal and mechanical results obtained by numerical simulation are in good agreement with experimental ones. Analysis of the influence of each pass on the plate distortion is discussed.

In this study, a numerical analysis of the performance of two Oscillating Water Column (OWC) wave energy converters, at different front and back wall slopes, was carried out. The first device had vertical front and back walls and the second one had its wall slopes of 40° in relation to the horizontal plane. The FLUENT® numerical model, which is based on the Reynolds-Averaged Navier-Stokes (RANS) equations, was used. The Volume of Fluid (VoF) method was employed to take into account free surface flows. The case study comprised a 10 m deep flume with an onshore OWC at its end, equipped with a Wells turbine. A 2D hydrodynamic mathematical model was employed and a 3D air pressure effect inside the OWC air-chamber was considered. Analyses of the hydrodynamics behavior, fluid-structure interaction outside (run-up/down, reflected waves) and inside the chamber (free surface elevation, sloshing) and energy distribution (pneumatic extracted energy, reflected wave energy and energy losses) were conducted. Results showed that the device with inclined walls had the best efficiency in comparison with the other one. However, the latter showed lower variation in efficiency in the wave period range than the former.

The technique of weaving by magnetic arc deflection was developed a few years ago to enable the oscillation of the weld pool, thus, causing grain refinement and improving the properties on the welded joint. This paper aims to propose two heat source models that include effects of magnetic arc deflection on a bead-on-plate GTAW process in numerical simulations by using the finite element method. Two cases are studied. In the first case, non-deflected arc and straigth magnectic deflected arc along the torch movement are carried out and compared to numerical simulations. Temperatures at three different points on the backside of the plates (two away from the welding center line and one in its center) and weld pools of SAE 1020 3.2 mm and 6 mm thick steel plates are analyzed. Results obtained by numerical simulations are close to the experimental ones. In the second case, welding with weaving (frequency of 1Hz) on 3 mm thick steel plates is analyzed. The bead width and its visual presentation are compared to experimental results, which show good agreement with both proposed models. Resumo A técnica de tecimento por deflexão magnética do arco foi desenvolvida há alguns anos para permitir a oscilação da poça fundida, causando o refinamento de grão e melhorando as propriedades da junta soldada. Este artigo tem como objetivo propor dois modelos de fontes de calor que inclui os efeitos de deflexão magnética do arco em um processo GTAW sobre chapa nas simulações numéricas pelo uso do método dos elementos finitos. Dois casos são estudados. No primeiro, são comparadas as simulações numéricas para o arco sem deflexão e para o arco com deflexão magnética fixa ao longo do movimento da tocha. São analisadas as temperaturas em três pontos na parte inferior da chapa (dois afastados da linha de centro de soldagem e outro no centro) e poças de fusão para chapas de aço SAE 1020 e espessuras de 3,2 e 6 mm. Os resultados obtidos pelas simulações numéricas estão muito próximos aos experimentais. No segundo caso, é analisada a soldagem com tecimento (frequência de 1Hz) em chapas de aço de 3 mm de espessura. São comparadas as larguras do cordão e sua forma geométrica com os resultados experimentais, que mostram a boa concordância obtida pelos dois modelos propostos.

Welding processes are considered a thermal-mechanical-metallurgical coupled issue. The most important boundary condition in the numerical thermal analysis is the heat source model. Although many studies have been carried out to propose different types of heat source models, the limitations of each model application have not been clearly specified. The Gaussian heat source is a model in which heat is generated over a surface; therefore, it may not be suitable to be applied to thick plates. In this study, the accuracy of the Gaussian heat source model is investigated in bead-on-plate welding by the TIG process. Analyses are performed by the ANSYS® software, considering the convection and the radiation phenomena. Several cases with different parameters of heat distribution, heat input and plate thickness have had their weld pool geometries analysed and compared with those obtained experimentally. Analyses of the influence of the radial distance from the center of the Gaussian heat source and the thickness of the plate on the bead width and the penetrated depth of the fusion zone boundary are presented. Results have shown the adequacy and the limitations of the Gaussian heat source model in the welding simulation. Keywords: welding process, numerical simulation, heat source model, ANSYS® software. RESUMO Os processos de soldagem sao considerados problemas termo-mecânico-metalurgicos acoplados. A condicao de contorno mais importante na analise termica numerica e o modelo de fonte de calor. Embora muitos estudos tenham sido realizados com o objetivo de propor diferentes tipos de modelos de fontes de calor, a limitacao da aplicacao de cada modelo nao e claramente conhecida. A fonte de calor Gaussiana e um modelo no qual o calor e gerado sobre uma superficie; por esta razao, ela nao e adequada para aplicacoes em chapas espessas. Neste estudo, e investigada a acuracia do modelo de fonte de calor Gaussiana em uma soldagem do tipo cordao sobre chapa pelo uso do processo TIG. As analises foram realizadas por meio do programa computacional ANSYS®, considerando os fenomenos de conveccao e de radiacao. Para diversos casos com diferentes parâmetros de distribuicao de calor, intensidades de fluxos de calor e espessuras de chapa, sao analisadas as geometrias transversais do cordao de solda e estas sao comparadas com aquelas obtidas experimentalmente. Sao apresentadas as analises das influencias da distância radial do centro da fonte de calor Gaussiana e das espessuras das chapas na largura e na penetracao do cordao de solda. Os resultados mostram a aplicabilidade e as limitacoes do modelo de fonte de calor Gaussiana na simulacao da soldagem. Palavras-chave: processo de soldagem, simulacao numerica, modelo de fonte de calor, programa computacional ANSYS®.

The growing search for clean and renewable energy sources has given rise to the studies of exploring sea wave energy. This paper is concerned with the numerical evaluation of the main operational principle of a submerged plate employed for the conversion of wave energy into electrical one. The numerical model used to solve the conservation equations of mass, momentum and transport of volume fraction is based on the finite volume method (FVM). In order to tackle with the flow of mixture of air-water and its interaction with the device, the multiphase model volume of fluid (VOF) is employed. The purpose of this study is the evaluation of a numerical model for improvement of the knowledge about the submerged plate wave energy converter, as well as the investigation of the effect of the distance from the plate to the bottom of the sea (H P) on the performance of the converter. The simulations for several distances of the plate from the seabed show that the optimal efficiency is 64%, which is obtained for H P=0.53 m (88% of the depth). This efficiency is 17% larger than that found in the worst case (H P=0.46 m, 77% of the depth).

The study of ways of converting ocean wave energy into a useful one and the improvement of the existing equipment are complex engineering problems and very important issues in today's society. In this paper, the onshore oscillating water column device, in a 10 m deep channel subjected to 1 m high incident wave and wave periods from 4 s to 15 s, is investigated. The numerical analyses are carried out using Fluinco model that deals with incompressible flow problems based on the Navier–Stokes equations and employs the two-step semi-implicit Taylor–Galerkin method. An aerodynamic model is implemented in the algorithm to determine the air pressure that is imposed on the free surface. Analyses are divided into two sections. In the first section, the flow variables obtained by Fluinco and the commercial model Fluent are compared and similar results are obtained. In the second section, an investigation of the chamber geometry and turbine characteristic relation that provide the best device performance is carried out. In this case, variations in the front wall depth, the chamber length, the turbine characteristic relation and the chamber height, are made.

This case study analyses the structural behavior of a supporting system for modularized process plants used in ship shaped floating oil production units, through the monitoring of strain and relative displacements on the support structures of the modules on the deck, called stools. The target of this study is the platform P-53 from PETROBRAS. It is a 346 m long converted unit, turret-moored, and its oil production capacity is 180,000 bpd. Each module of its process plant is supported by four stools, two sliding ones and two fixed ones. A system for data acquisition was implemented to carry out this monitoring; 75 sensors such as strain gauges, displacement transducers and accelerometers were installed on the platform. Measurements were carried out during the installation of the modules upon the hull in the shipyard and in its final location, under the operational and environmental conditions of the Campos Basin (Rio de Janeiro, Brazil). No relative displacement between the sliding stools and the module pads was recorded throughout the monitoring period. This paper aims at contributing to the structural design of the modules and their supports on the deck. Besides, this paper can contribute to reviewing future projects.

The parabolic mild-slope model Refdif_S simulates the propagation and deformation of irregular waves in coastal regions with variable water depth. PY_Refdif_S software tool is an extension of the model, using a multi-grid approach in order to achieve a more efficient and applicable model to large areas and a large set of different wave conditions. The tool is made up of several Python routines that automatically build multiple grids, prepare data files and execute Refdif_S for several sea states. The model was applied to the study of irregular wave propagation from offshore to nearshore in the region of Torres-Mostardas, Brazil. For a range of irregular incident sea states, several calculations with the tool were performed. The wave field and local sea states were characterised in that area. Based on this application, advantages and limitations of the tool are analysed.

An algorithm to simulate 3D fluid–structure interaction problems using the finite element technique is presented in this work. A two-step Taylor–Galerkin scheme and linear tetrahedra elements are employed to analyze the fluid flow, which may be high or slightly compressible. An arbitrary Lagrangean–Eulerian (ALE) formulation is adopted, which must be compatible with the motion of the fluid–structure interface. A fractional method with velocity correction is used for incompressible fluids. The structure is analyzed using triangular elements with three nodes and six degrees of freedom in each node (three displacement components and three rotation components). Geometrically non-linear effects are included. The Newmark method is employed to integrate in time the dynamic equilibrium equations using an updated Lagrangean description. The algebraic system of equations is solved using the conjugated gradient method and an incremental-iterative scheme is used to solve the non-linear system resulting from finite displacements and rotations. The code is optimized to take advantages of vector processors. Some cases studies have been considered for validation of the computational algorithm. A two-dimensional supersonic flow over a clamped flat plate is analyzed in order to study the aeroelastic behavior of this plate. Vibrations due to wind action of an inflated membrane as well as vortex inducing vibrations in a panel immersed in a slightly compressible fluid are also studied.

The shoreface and the inner shelf along the northern and the central coast of Rio Grande do Sul (RS) state, Brazil, between Torres and Mostardas, although displaying a homogeneous bottom relief show variations in slope and width. In the northern sector, between Torres and Pinhal, the inner shelf is wide, while the shoreface is narrow. Towards the south, these patterns are just the opposite. In this study, a model based on the parabolic approximation of the mild slope equation, REF/DIF.1, is used to simulate the wave propagation in this region. Wave refraction diagrams based on the predominant wave climate show a dominant and invariable divergent pattern for wave incidence from 90° to 135°. Numerical analyses of changes in wave energy, regarding differences in width and slope using a bottom friction coefficient fw = 0.01 in the different coastal sectors, show little influence of the bottom friction over the wave transformation processes. In general, a friction coefficient fw = 0.2 shows that wave energy reduction due to bottom friction over the wider shoreface south of Pinhal by comparison with the sector to the north is compensated by its shorter inner shelf width. The analyses show that lateral gradients of wave energy along the 10 m isobaths regarding the morphological differences between the two sectors are negligible., A plataforma continental interna e a antepraia ao longo do litoral norte e médio do estado do Rio Grande do Sul (RS), Brasil, entre Torres e Mostardas, têm o relevo do fundo homogêneo, mas apresentam variações de inclinação e largura. No setor norte, entre Torres e Pinhal, a plataforma interna é mais larga, enquanto a largura de antepraia é mais estreita. Por outro lado, o oposto ocorre ao Sul de Pinhal. Este trabalho analisa numericamente a propagação de ondas nesta região através do REF/DIF 1, modelo que adota a aproximação parabólica da equação de declive suave. Os diagramas de refração de ondas, baseados em um clima de onda predominante, indicam que o padrão dominante é o divergente para ondas incidentes de 90° a 135°. Análises numéricas das variações de energia de ondas, investigando a influência das variações da largura da plataforma interna e da largura de antepraia, e da fricção com o fundo considerando um coeficiente de atrito fw = 0,01, revelam a pouca influência do atrito com o fundo sobre a transformação das ondas. Adotando-se um coeficiente de atrito fw = 0,2, constata-se, de forma geral, que a influência do aumento da largura da antepraia do sul de Pinhal para o norte no atrito com o fundo é compensada pela influência da diminuição da largura da plataforma continental interna. As análises mostram que os gradientes laterais da energia da onda ao longo da isobatimétrica de 10 m, mesmo considerando as diferenças morfológicas entre os dois setores, são desprezíveis.

An algorithm to simulate three-dimensional high compressible flows using the finite element method and a multi-time-step integration technique with subcycles is presented in this work. An explicit two-step Taylor–Galerkin scheme is adopted to integrate in time the continuum equations. When explicit schemes are used, the time-steps must satisfy the CFL stability conditions. If the smallest critical time-step is adopted uniformly for the whole domain, the integration scheme may consume a large amount of CPU time. Multi-time-step integration techniques are very suitable in these cases because elements and nodes are separated into several groups and a different time-step is assigned to each group. In this way, each group of elements is integrated with a time interval which is much closer to the critical time-steps of the elements in the group. This results in great computational savings, mainly when element sizes and properties are very different, leading to significant differences in the local critical time-step values. Multi-time-steps integration techniques are also very useful in transient problems, taking into account that at the end of each subcycle, values of the unknowns at the same time level are obtained. The multi-time-step algorithm is applied to analyze the supersonic flow (Mach=8.5) past a sphere immersed in a non-viscous flow, and the results and computational performance are compared with those obtained when a uniform time-step is used over the whole domain.

The vortex-induced vibration (VIV) phenomenon has drawn the attention of researchers in Engineering for several decades. An example is the riser used for petroleum exploration, in which it is subjected to marine flows that may cause oscillations due to vortex shedding. In this paper, numerical analyses of the phenomena that occur in the interaction among flows at low Reynolds numbers and elastically mounted cylinders are presented. The simulation is carried out by using the numerical model Ifeinco that uses a semi-implicit two-step Taylor-Galerkin method to discretize the Navier-Stokes equations and the arbitrary Lagrangean-Eulerian formulation to follow the cylinder motion. The rigid body motion description is calculated by using the Newmark method. Firstly, the characteristics of the vortex generation process for the fixed cylinder are analyzed. In this case, the Strouhal number, the mean drag and the RMS lift coefficients for Reynolds numbers ranging from 90 to 140 are shown. Afterwards, an analysis of a flexible supported cylinder (with a spring and a damper) in transverse direction subject to flows with Reynolds numbers ranging from 90 to 140 is carried out. The cylinder displacement and the vibration frequencies are studied; the synchronization between the vortex shedding and the vibration frequency (lock-in) is analyzed. Similar results to the experimental ones developed by Anagnostopoulos and Bearman (1992) were obtained in this study. 10 0 61-67pp Vol. 11 • No. 1-2 DHA/NPE Engenharia Térmica (Thermal Engineering)

The augmentation of energy demand and the Kyoto agreement to reduce the greenhouse gas emissions have increased the interest for the study of renewable energy [1]. The growth and interest in expanding the wave energy sector are based on its potential estimated to be up to 10 TW. Depending on what is considered to be exploitable, this covers from 15 to 66 % of the total world energy consumption referred to 2006 [2–4]. According to ref. [5] the wave energy level is usually expressed as power per unit length (along the wave crest or along the shoreline direction). Typical values for “good” offshore locations (annual average) range between 20 and 70 kW/m and occur mostly in moderate to high latitudes. In this sense, the southern coasts of South America, Africa, and Australia are particularly attractive for wave energy exploitation.

A numerical simulation of the interaction between a regular wave and an immersed horizontal cylinder, whose axis is 3-radius deep, perpendicular to the direction of the wave propagation, is presented in this paper. The numerical model uses the semi-implicit two-step Taylor- Galerkin method to integrate Navier-Stokes equations in time and space. Arbitrary lagrangean-eulerian formulation is employed to describe the free surface movement. The free surface elevations near the cylinder and in some gauges along the channel, as well the spectrum distribution, are compared with experimental ones, and good agreement is obtained. The analysis shows that the viscous effects only affect the area that is very close to the cylinder.

Geometrically nonlinear static and dynamic behaviour of laminate composite shells are analyzed in this work using the Finite Element Method (FEM). Triangular elements with three nodes and six degrees of freedom per node (three displacement and three rotation components) are used. For static analysis the nonlinear equilibrium equations are solved using the Generalized Displacement Control Method (GDCM) while the dynamic solution is performed using the classical Newmark Method with an Updated Lagrangean Formulation (ULF). The system of equations is solved using the Gradient Cojugate Method (GCM) and in nonlinear cases with finite rotations and displacements an iterative-incremental scheme is employed. Numerical examples are presented and compared with results obtained by other authors with different kind of elements and different schemes.

O objetivo deste trabalho é avaliar o processo de adesão microbiana que ocorre sobre superfícies de aços austeníticos AISI 304 usados na fabricação de tanques e trocadores de calor em laticínios que beneficiam o leite em natura e/ou na fabricação de queijo. A própria natureza do material tratado (leite cru) favorece o crescimento de microrganismos formadores de biofilmes. O processo de adesão foi verificado in loco em trocadores e em tanques de recebimento e resfriamento do produto. Para avaliar a formação do biofilme e correlacionar com o processo de soldagem, foram depositados cordões sobre chapa de aço inoxidável 304, utilizando-se o processo MIG/MAG. Após as soldagens, as placas de teste foram imersas em tanques de recebimento do leite cru, permanecendo expostas durante 06h. As chapas foram submetidas aos processos de CIP (clean in place), da mesma maneira que os tanques de contenção e recebimento. Avaliações microbiológicas foram realizadas, bem como a coleta de Swabnas áreas da ZAC (zona afetada pelo calor) e reforço de raiz, jápré-determinadas visando identificar a adesão microbiológica. Estabeleceu-se o conceito de coeficiente de partição para a interface superfície soldada, biofilme e fluxo de leite. Criou-se o conceito de ADPS (Adesão Preferencial na Solda) visando estabelecer uma correlação entre a posição de adesão microbiana, com a respectiva formação do biofilme versus a área de soldagem, como ZAC, reforço de raiz ou material de base. A partir dos resultados obtidos identificou-se a área preferencial de adesão e quais as variáveis responsáveis por tal efeito. The objective of this work is to evaluate the microbial adhesion process that occurs on surfaces of AISI 304 austenitic steels used in the manufacture of tanks and heat exchangers in dairy products that benefit the milk in nature and / or cheese production. The very nature of the treated material (raw milk) favors the growth of biofilm-forming microorganisms. The adhesion process was verified in loco in exchangers and in receiving and cooling tanks of the product. To evaluate the formation of the biofilm and to correlate with the welding process, strands were deposited on 304 stainless steel sheet using the MIG / MAG process. After the welds, the test plates were immersed in receiving tanks of the raw milk, remaining exposed for 06 hours. The plates were subjected to CIP (clean in place) processes, in the same way as containment and receiving tanks. Microbiological evaluations were performed, as well as the collection of Swab in the zones of the ZAC (zone affected by heat) and root reinforcement, already predetermined in order to identify the microbiological adhesion. The concept of partition coefficient for the welded surface interface, biofilm and milk flow was established. The concept of ADPS (Preferential Adhesion in Welding) was created in order to establish a correlation between the position of microbial adhesion, with the respective formation of the biofilm versus the area of welding, as ZAC, root reinforcement or base material. From the obtained results the preferential adhesion area was identified and the variables responsible for such effect. Tese (Doutorado) 2018-01-10