bluuebunny/crossref_metadata_2025 huggingface dataset:
AERODYNAMICS AND AEROACOUSTICS SURVEY FOR A LOW SPEED SUBSONIC JET OPERATING AT MACH 0.25
Authors: Proença A. R. , De almeida O. , Self R. H.
Published: November 2018

The purpose of this work is to study and characterize, in laboratory, the aerodynamics of a free jet operating at subsonic regime and identify its acoustic signature. This study aims to analyze the fundamental role of turbulent flow structures in the total noise produced at different Mach numbers. This work is focused at low speed subsonic jets operating at Mach number 0.25. The research is done by analyzing the data obtained in experiments using Pitot tube, hot-wire anemometer and acoustic measurements. This work also describes the experimental procedures for each step of analysis, as well as the characteristics of jet noise facility. The data from measurements with Pitot tube is used to study the mean velocity profiles. The average properties are also analyzed with anemometry system, likewise used to study the turbulent intensity of eleven axial lines, ranging from the center line to the edge of the nozzle (lipline). These results are compared with the literature and is verified the accuracy of hot-wire anemometers for turbulent intensities lower than 15%. A database with the sound pressure level as a function of frequency is constructed from experiments serving as data for further numerical analysis to solve this problem.
CONTRIBUTIONS TO THE MARINE PROPELLERS HYDRODYNAMIC DESIGN
Authors: Favacho B. I. , Vaz J. R. P. , Mesquita A. L. A.
Published: November 2018

The navigation in Amazon region is very important due to the length of navigable rivers and the lack of alternative road network, as well as being a form of transportation costless for the flow of agricultural and manufacturing production. This kind of transportation present social, economic and technological importance for this region. Thus, this work objective to develop a mathematical approach for the marine propellers design, using a formulation for chord and pitch angle optimization, taken into account the equations of mass, energy and momentum balance for the theoretical calculation of thrust and torque relationships on an annular control volume, ie, the mathematical model is based in the Blade Element Momentum (BEM) theory. The proposed hydrodynamic model present low computational cost and it is easy to implement. The results are compared with classical Glauert's theory and the experimental data of the Wageningen B3-50 propeller, presenting good agreement.
AN ANALYTICAL TEMPERATURE SOLUTION ANALYSIS FOR A MULTILAYER HEAT CONDUCTION PROBLEM
Authors: Oliveira G. C. , Fernandes A. P. , Guimarães G.
Published: November 2018

This paper presents a method of obtaining an analytic temperature solution for a two-layer heat conduction problem. Obtaining the temperature analytical solution for a multilayer heat conduction problem is not a direct method. The way to indentify the eigenvalues and to derive the Green function solution equation requires a different treatment since there are more than one domain to solve. This work presents a solution of a thermal twolayer problem based on Green’s functions.
CONSTRUCTAL DESIGN AND SIMULATED ANNEALING EMPLOYED FOR GEOMETRIC OPTIMIZATION OF A Y-SHAPED CAVITY INTRUDED INTO CONDUCTIVE WALL
Authors: Gonzales G. V. , Dos Santos E. D. , Emmendorfer L. R. , Isoldi L. A. , Estrada E. S. D. , Rocha L. A. O.
Published: November 2018

he problem study here is concerned with the geometrical evaluation of an isothermal Y-shaped cavity intruded into conducting solid wall with internal heat generation. The cavity acts as a sink of the heat generated into the solid. The main purpose here is to minimize the maximal excess of temperature (θmax) in the solid. Constructal Design, which is based on the objective and constraints principle, is employed to evaluate the geometries of Y-shaped cavity. Meanwhile, Simulated Annealing (SA) algorithm is employed as optimization method to seek for the best shapes. To validate the SA methodology, the results obtained with SA are compared with those achieved with Genetic Algorithm (GA) and Exaustive Search (ES) in recent studies of literature. The comparison between the optimization methods (SA, GA and ES) showed that Simulated Annealing is highly effective in the search for the optimal shapes of the studied case.
WAVE PROPAGATION ON A FLUME: NUMERICAL SIMULATION
Authors: Conde J. M. P. , Roberto P. T. S. , Fortes C. J. E. M.
Published: November 2018

This paper presents the numerical simulations done by using the waves2Foam, an OpenFOAM® library, to simulate the propagation of regular waves without breaking in a three-dimensional flume. The numerical code solves the unsteady Navier-Stokes equations and uses a Volume-of-Fluid (VoF) method to identify the free-surface. A regular incident wave with a 1.5s period and 0.1m wave height was considered. This is one of the conditions, from the wide range of wave flume tests conducted at the National Laboratory for Civil Engineering (LNEC), whose objective was to analyze the hydrodynamics of wave transformation and wave breaking for different incident conditions over a variable bathymetry. Comparisons are made between the numerical and the experimental results. These comparisons include time-series of wave-gauges records at several locations along the flume and the corresponding amplitude spectra; significant wave height and average period evolution along the flume; time-series of the velocity components at one section of the flume, measured at the middle of the water column; and hodograph representation of the velocity components, in the middle of the water column, in the xy, xz, and yz planes, along the flume. It was found that the numerical results obtained are close to the experimental data. The observed differences are attributable to numerical inaccuracies as well as the differences between the wave generation method in the numerical and experimental tests.
NUMERICAL STUDY OF THE INFLUENCE OF GEOMETRIC PARAMETERS ON THE AVALIABLE POWER IN A SOLAR CHIMNEY
Authors: Vieira R. S. , Garcia C. , Junior I. C. A. , Souza J. A. , Rocha L. A. O. , Isoldi L. A. , Dos Santos E. D.
Published: November 2018

In the presented work, it is made a numerical study about the main physical principle of a solar chimney (SCPP – Solar Chimney Power Plant) and the influence of some geometric parameters on the available power in the SCPP. The main objectives are to test the applicability of the studied numerical model in future studies of SCPP geometric optimization and to test the action of the collector inlet height (H1) and the chimney outlet diameter (D2) on the available power of the device. For that it is considered an incompressible, turbulent, steady flow with mixed convective heat transfer in a two-dimensional and axisymmetric domain, similar to the one found in a solar chimney. The conservation equations of mass, momentum and energy are numerically solved using the finite volume method, more specifically with the FLUENT software. The classical turbulence modeling (RANS) was used for the turbulence approach with standard model k – ε. The other geometric parameters: collector radius (R) and the inlet and outlet of the turbine section, R1 and R2, are also constant. The verification results indicated a good agreement with those presented in the literature, even using a simplified domain. It was also observed that the H1 parameter is almost insensitive in the solar chimney performance, whereas the D2 variable presented great influence in the available power. The best performance was attained for an intermediate value of D2, D2 = 0.44 m. For this value, the available power was almost 72% and 19% higher from those obtained in the inferior and superior extremes of the studied D2 variable, D2 = 0.22 m and 0.88 m, respectively. It was also observed that there is a very good possibility of optimization of the chimney geometry in future studies.
POLYMER DEGRADATION IN TURBULENT DRAG REDUCING FLOWS IN PIPES
Authors: Sandoval G. A. B. , Trevelin R. , Soares E. J. , Silveira L. , Thomaz F. , Pereira A. S.
Published: November 2018

The drag reduction by addition of high molecular additives has been investigated by a number of researchers since it was reported by Toms more than 60 years ago. One of the most significant limitations in drag reduction is the polymer degradation, which is caused by the turbulent structures. Researches have demonstrated that many parameters affect the polymer efficient, as: molecular weight, Reynolds number, concentration and temperature. In the present work we investigate this degradation phenomenon in a pipe flow apparatus device, for aqueous solutions of three different polymers: Polyethylene Oxide (PEO), Polyacrylamide (PAM) and Xanthan Gum (XG).The first two are known as flexible molecules while the last one is considered rigid. The dependence of polymer scission on molecular weight, concentration and Reynolds number is analyzed. We report how the drag reduction decreases when the flow pass repeatedly through the pipe and how the pressure loss measured in the apparatus increases, despite to the fact that the experiment was conducted at a fixed inlet pressure. It is worth noting that the mechanism of loss of efficiency for the XG solutions seems to be completely different from that observed for PEO and PAM, the flexible materials.
MATHEMATICAL MODELING OF THE DRYING CURVES OF FOXTAIL MILLET SEEDS IN SPOUTED BED
Authors: Do Nascimento L. D. , Corumbá L. G. , Rocha S. C. S. , Taranto O. P. , Costa C. M. L. , De Faria L. J. G.
Published: November 2018

In order to provide a contribution to future studies of foxtail millet (Setaria italica), the drying kinetics of the seeds was investigated at three different temperatures: 44, 65 and 86°C. The seeds of S. italica with a moisture equal to 30% in dry basis were dried in a conical-cylindrical spouted bed during an interval of 132 min. Some empirical mathematical models were selected to describe the experimental drying kinetics data (Lewis, Henderson and Pabis, Page, Diffusion approach, Midilli and Wang and Singh) and the best models were chosen according to the statistical tests results (coefficient of determination, mean relative percent deviation, mean square root error and residue distribution), using the software Statistica® 7.0 and applying the Quasi-Newton method. Only the decreasing rate period was observed in the drying kinetic curves, indicating that the removal of moisture content was preferably by the diffusion mechanism, which is a characteristic behavior of fibrous products, like the agricultural products. The models of Diffusion Aproach, Page and Midilli were the most suitable to describe the experimental drying curves.
RHEOLOGICAL ANALYSIS OF VEGETABLE OILS USED FOR BIODIESEL PRODUCTION IN BRAZIL
Authors: Silva L. E. , Santos C. A. C. , Ribeiro J. E. S. , Souza C. C. , Sant’Ana A. M. S.
Published: November 2018

Rheology attempts to define a relationship between the stress acting on a given material and the resulting deformation and/or flow that takes place. Thus, the knowledge of rheological properties of fluid materials such as vegetable oils generates auxiliary data that can be used in its storage and application. In this context, the aim of this study was to evaluate the rheological behavior of vegetable oils (cotton, canola, sunflower, corn and soybean) at different temperatures, using four rheological models (Ostwald- de-Waelle, Herschel-Bulkley, Newton and Bingham). The rheological properties were determined using a Thermo Haake rheometer with concentric cylinder geometry. Measurements were taken at 30, 45 and 60 °C by controlling the temperature using a thermostatic bath coupled to the equipment. The software Rheowin Pro Job Manager was used for process control and data record. The rheograms were obtained by measuring the values of shear stress varying the shear rate from 100 to 600 s-1 within 250 seconds. For the analysis of the apparent viscosity at different shear rates was applied simple linear regression until 2nd degree with the aid of SAS (SAS/Stat 9.2) program. The apparent viscosity data were submitted to analysis of variance and the averages were compared by Tukey test at 5% of probability. Higher temperatures of the samples were correlated to lower shear stress values, hence lower values for viscosity and consistency index were obtained, since it is known that the density and viscosity are highly sensitive to temperature and that the increase in temperature results in reduction of viscosity, benefiting the fluid flow. The models of Newton and Ostwald-de-Waelle were chosen to evaluate the rheological behavior of the samples, showing a good fit for the rheological data.
TRANSIENT MODELING OF A SMALL HYDROKINETIC TURBINE
Authors: Vaz J. R. P. , Moreira T. H. S. , Brandão D. T. , Lopes J. J. A. , Figueiredo S. W. O. , Mesquita A. L. A. , Galhardo M. A. B. , Blanco C. J. C.
Published: November 2018

In recent years, great attention has been given to the study of hydrokinetic turbines for power generation. Such importance is due to the use of clean energy technology by using renewable sources. Therefore, this work aims to present a relevant methodology for the efficient design of horizontal-axis hydrokinetic turbines with variable rotational speed. This methodology includes the Blade Element Method (BEM) for determining the turbine power coefficient, since BEM is widely used in the hydrokinetic turbine design due to its good agreement with experimental data. In addition, the dynamic equation of the driveline is used, taking into account the BEM to provide the rotor hydrodynamic torque coupled with the drive train model, including the multiplier and the electric generator. In this case, the modeling of the whole system comprises the hydrodynamic information of the rotor, the mass-moment of inertia, frictional losses and electromagnetic torque imposed by the generator. The theoretical results were obtained for the transient rotational speed and compared with field data measured from small hydrokinetic turbine installed at the Arapiranga-Açu creek, which is located in the city of Acará, Pará, Brazil.
INFLUENCE OF MODELING OF TURBULENCE IN THE FLOW PARAMETERS WITHIN A FOOD OVEN USING THE OPENFOAM®
Authors: Verdério Jr S. A. , Scalon V. L. , Padilha A.
Published: November 2018

Because of the better flexibility in warming and high production, the continuous furnace tunnel is the better option to the processing of industrialized food products. This study presents a numerical investigation of the effects of RANS turbulence modeling on the main parameters of the air flow inside a continuous oven with indirect heating - velocities, temperatures, streamlines and heat flows by convection and radiation. The geometry and operating conditions used for constructing the model, setting the mesh and initial and boundary conditions were obtained based on values of operating ovens. Modeling consider the hypothesis of air as an ideal gas, incompressible and Newtonian; the equations of continuity, momentum balance and energy in turbulent regime; closing model of two equations κ- ε and radiation model viewFactor. Utilized the free open source software OpenFOAM® for device modeling. The Rayleigh Number of the cavity was used to evaluate the treatment indicated to turbulence. Considering the results obtained, the inclusion of model κ- ε stabilized the velocity fields and temperatures around the average value. In relation to the heat exchanges involved, heat flow by convection on the mat showed negligible compared to the effects of radiation. Due to the discrepancy between the orders of magnitude of convection and radiation, it's difficult the precise evaluation of the first, because small fluctuations in temperature and velocity affect considerably and induce oscillations in their behavior. However, the radiation model attained good approximation the most relevant exchanges, showing a good chance their application in practical cases.
ANALYSIS OF THE ELECTRICAL CHARACTERISTICS IN MULTIPHASE FLOW THROUGH THE WIRE-MESH SENSOR
Authors: Cely M. M. H. , Velasco H. F. P. , Rodriguez O. M. H.
Published: November 2018

Many studies on the characterization of electrical properties of multiphase fluid are found in the literature. One of the main motivations of these efforts has been the development of instrumentation for the measurement of volumetric fraction using electrical sensors. Although one can find a variety of instruments for that purpose, relatively few works in the open literature present studies on the best range of measurement frequency and its effect on permittivity models. An experimental and theoretical study is presented, where the best frequency to measure the volumetric fraction in two and three-phase mixtures is selected. Several permittivity models are applied to measure the volumetric fraction. The fluids used in the experiments were tap water, deionized water, mineral oil, isopropyl alcohol and hexane. Known volumes of fluids were mixed until obtaining a homogeneous mixture. The data were taken by a 1×4 wire-mesh sensor (WMS) immersed in the mixture. The WMS had a gap between planes of 1.4 mm, the wires were 3 mm apart from each other and the diameter of the wires was of 0.2 mm. The experimental system consisted of a generator, an oscilloscope and conditioning circuits (formed by operational amplifiers). A frequency scan was performed between 7000 Hz and 20 MHz for each mixture. A total of 60 logarithmically spaced frequencies were applied.
APPLICATION OF THE LINEAR SPRING-DASHPOT MODEL IN THE CFD-DEM SIMULATION OF ALUMINA FLUIDIZATION
Authors: Branco Jr A. M. C. , Mesquita A. L. A. , Vaz J. R. P.
Published: November 2018

The coupling of the Computational Fluid Dynamics (CFD) to the Discrete Element Method (DEM) to simulate fluidization is computationally demanding. Although the Linear Spring-Dahspot (LSD) model can help to reduce the CFD-DEM simulation runtime due to its simplicity, its applicability is not reasonable for all sorts of problems. The objective of the present work is to show the application of the LSD model to the CFD-DEM simulation of alumina fluidization. The simulations were carried out with the software ANSYS FLUENT 14.5 and divided into two parts: (1) the reproduction with ANSYS FLUENT of simulations from the literature in which the LSD model and a representative particle approach were used. (2) the simulation of alumina fluidization and validation with experimental data. The results of three main sets of parameters were analysed to include different DEM and CFD time steps, drag models, the representation of particles with both uniform size and particle size distribution, etc. The main conclusion of this work is that the LSD model and the CFD-DEM approach can be used to model the actual behaviour of alumina fluidized beds, but the high simulation runtime and the correct setting of the strategies used to control it are still limiting factors which deserve special attention.
NUMERICAL STUDY CONCERNING THERMAL RESPONSES OF NANOFILMS UNDER THE THERMOMASS THEORY
Authors: Freitas R. S. M. , Stampa C. S. , Lobão D. C. , Alvarez G. B.
Published: November 2018

he Thermomass theory is based on the relationship mass-energy of Einstein, i.e., the heat has mass-energy duality, behaving as energy in processes where its conversion occurs in another form of energy, and behaving as mass in heat transfer processes. The mathematical model stablished by the Thermomass model falls within the class of problems called models non-Fourier heat conduction. The present work aims to analyze the thermal responses provided by Thermomass theory of nanofilms submitted to a very fast heating process using two different heat sources (laser pulses). During the process of analysis, the equations are written in conservation law, put into dimensionless form and discretized in the way that a high-order TVD scheme is used on to provide accurate and reliable numerical simulations for obtaining the thermal responses predicted by the Thermomass model. The results show that the Thermomass theory predicted a heterogeneous temperature distribution with elevated temperature peaks. The thermal responses obtained from this model may prevent the thermal damage caused by technologies of the processing and manufacturing of elements based on high-power laser applications.
WAVELET ANALYSIS CONSIDERATIONS FOR EXPERIMENTAL NONSTATIONARY FLOW PHENOMENA
Authors: Indrusiak M. L. S. , Kozakevicius A. J. , Möller S. V.
Published: November 2018

In this work, wavelet transforms are the analysis tools for studying transient and discontinuous phenomena associated to turbulent flows. The application in quest results from velocity measurements with hot wire anemometry in the transient wake considering a circular cylinder in an aerodynamic channel. Continuous and discrete wavelet transforms are applied and compared with the corresponding results given by the Fourier transform. For the continuous wavelet transform, the Morlet function was adopted as transform basis, and for the discrete case, the Daubechies orthonormal wavelet with 20 null moments. Results using the discrete wavelet packet transform are also presented and compared. A wake past a cylinder was analytically simulated and compared with the actual one, both in transient flow. The ability of the wavelet transforms in the analysis of unsteady phenomena and the potential of the wavelet approach as a complementary tool to the Fourier spectrum for the analysis of stationary phenomena is presented and discussed.
EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF HEAT SINK GEOMETRIC PARAMETERS ON NATURAL CONVECTION
Authors: Silva V. A. , Anselmo B. C. S. , Silva A. L. F. L. , Silva S. M. M. L.
Published: November 2018

In this work, the steady state heat transfer by natural convection in heat sinks with rectangular fins positioned vertically and horizontally was studied. The heat transfer by radiation was also considered. Several analyses were performed to determine the optimal number and position of the sensors used to measure the temperature on the heat sinks horizontally and vertically positioned. These analyses confirmed an almost uniform temperature distribution in the heat sink. This uniformity allowed the use of thermocouples only in the center of the heat sink. Twelve heat sinks were designed to study how their geometric parameters such as height, spacing and thickness of the fins, influence the heat transfer by free convection. In addition, in this work, two correlations using the dimensionless parameters Nusselt and Rayleigh are proposed. These correlations were obtained by using the results from the 12 heat sinks vertically and horizontally positioned considering a temperature range between 20 °C and 100 °C. Furthermore, studies were done to identify which of the 12 analyzed heat sinks managed to remove the greatest amount of heat in a given temperature range. The results were compared with those obtained from empirical correlations found in literature.
A METHODOLOGY FOR SIMULATION AND ASSESSMENT OF CONCENTRATED SOLAR POWER PLANTS
Authors: Starke A. R. , Lemos L. F. L. , Colle S. , Reinaldo R. F. , Cardemil J. M. , Escobar R.
Published: November 2018

A thermal analysis of Concentrated Solar Power plants is conducted considering parabolic trough collectors (PTC), linear Fresnel collectors using direct steam generation scheme (LFC-DSG) and central receiver system using both molten nitrate salts (CRS-MNS) direct steam generation (CRS-DSG). The plant capacities were ranged from 50 to 800 MWth and the analysis focuses on the environmental conditions of selected locations in South America. Thus, the study considers a parametric analysis of the main design parameter for different plant scales, in terms of the thermal performance indicators as solar field aperture area, power block rating capacity and plant annual efficiencies. The annual production of the plants is calculated by using the Transient System Simulation program (TRNSYS), which considers a new component library developed for that purpose. This library is based in the open access models developed by the U.S National Renewable Energy Laboratory and currently employed by the System Advisor Model (SAM) program. In addition, a new fluid properties subroutine compatible with TRNSYS codes standards was developed, which uses the freeware CoolProp library. These approaches allowed to modify and create new configurations for CSP plants, e.g. thermal storage for the DSG scheme.
A TWO-DIMENSIONAL THERMODYNAMIC MODEL TO PREDICT HEART THERMAL RESPONSE DURING OPEN CHEST PROCEDURES
Authors: Dias F. G. , Vargas J. V. C. , Brioschi M. L.
Published: November 2018

In this work, the temperature distribution of the heart in an open chest surgery scenario is studied. It is also evaluated the cardiac thermal effects of the injection of a cooling liquid in the aorta root, which is used in infrared thermography. The finite element method was used to develop a model that predicts the temperature distribution modification in a 2-dimensional slice of the heart. This thermodynamic model allows the computational simulation of the thermal cardiac response to open chest procedures, which are required by cardiac surgery. The influence of several operating parameters (e.g., coronary flow rate, temperature) on the resulting thermal distribution is analyzed. Therefore, this analysis allows the identification of parameters that could be controlled to minimize the loss of energy, and consequently, avoiding the hazardous thermal distribution that could put the heart in danger during cardiac surgery.
EVALUATION OF ALTERNATIVE CONFIGURATIONS OF A WATER-OIL HEAT EXCHANGER SYSTEM
Authors: Gonçalves A. L. V. , Francisco A. S.
Published: November 2018

The success in performance of equipment at industrial facilities is associated with its capacity of normal operation. When some equipment is subject to maintenance at large cost, the operation is uninteresting or even impracticable. The heat exchanger is an equipment widely employed, which performs transfer of heat between two fluids at different temperatures, separated by a solid wall. In this work, we evaluate alternative configurations of a system of shell-and-tube heat exchangers, aiming to improve the performance of this system in economical point of view, and to mitigate the maintenance cost. We use the effectiveness method to obtain outlet temperature values, and compare such results with values measured in situ. We conclude that alternative configurations are feasible in order to improve the thermal performance of the system of heat exchangers, reducing installation cost.
REVIEW OF CFD SIMULATION OF OXY-COAL COMBUSTION FOR ELETRICAL POWER GENERATION: OPPORTUNITIES AND CHALLENGES
Authors: Nascimento F. S. , Nascimento M. A. R. , Coronado C. J. R. , Rodrigues L. O. , Carvalho Jr J. A. , Dias F. L G.
Published: November 2018

The oxy-combustion has generated significant interested for reduction of CO2 emission when the fossil fuel is coal, due to simplification on the separation process of CO2 from the flue gas, it can be more easily stored in reservoir. The CFD numerical simulation techniques in oxy-coal combustion has the potential to contribute to designers in cost savings and reduced computational time; Furthermore, such techniques also provide a robust tool for better understanding and description of the aerothermodynamics processes involved, as well as, aiding the design of most efficient furnaces. However, to obtain representative results of the physical phenomena, the numerical models employed by CFD needs to be suitable for oxy-coal combustion. So, the aim of the paper is to carry out a review of the recent models that are being used for turbulence, combustion and pollutant emissions. Moreover, it is shown a comparison of different results obtained in the numerical simulation of oxy-coal combustion among new models, existing models and experiments. The analysis of the models and experiments shows that the challenges that are still being faced to obtain better accuracy of numerical simulation results. Improvements in the models for oxy-coal combustion can be seen like potential opportunities to investigate and optimize the process that occur in the combustion.
LAMINAR FORCED CONVECTION IN HORIZONTAL CHANNEL WITH HEAT GENERATION PLATES COOLED BY WATER
Authors: Silva M. C. da , Novelli A. D. P.
Published: November 2018

This paper describes the study of the behavior of two-dimensional and parallel horizontal flat plates with uniform internal heat generation subjected to laminar forced convection of water. The governing equations are solved numerically using the finite volume technique with Power-Law interpolating scheme and the SIMPLE algorithm. After the simulations the temperature and velocity fields were obtained for various plates spacing and fluid inlet velocities, as well as the Nusselt number values.
FLOW CHARACTERIZATION FROM A NACA AIR INTAKE ASSEMBLED IN A CANARD TYPE AIRCRAFT
Authors: Almeida O. De , Souza P. R. C.
Published: November 2018

omputational aerodynamics analyses of a NACA air intake assembled in a canard type aircraft is performed in this work. Semi-empirical calculation through the ESDU (Engineering Science Database Unit) preceded the CFD simulations to define the geometric size of the air intake as well to check its efficiency and drag estimation. The NACA air inlet was considered one of the best options available for implementing in a canard type aircraft since it reduces aerodynamic drag by avoiding protuberances in the fuselage. Numerical studies were performed with the air intake mounted in the aircraft's fuselage at operational flight conditions. These simulations were performed using Reynolds-averaged Navier-Stokes (RANS) and turbulence modeling by using the k-ω SST (Shear-Stress Transport). Data analyses were based on the air inlet efficiency, drag estimation and mainly flow characterization. The numerical results helped to characterize the flow in a canard type aircraft showing that the NACA air intake yielded satisfactory performance with low drag. The approach applied in this work was a partnership with the Brazilian Aircraft Factory (FABE) and Federal University of Uberlândia (UFU) to improve the design of a canard type aircraft. The CFD results have been corroborated by an empirical approach and with some experimental tests performed by the company, pointing towards the reliability of a very efficient design tool for application in industry.
NUMERICAL ANALYSIS OF LIQUID FRACTION AND HEAT FLUX IN THE SOLIDIFICATION PROCESS OF ERYTHRITOL IN SPHERES
Authors: Ehms J. H. N. , Bodnar F. A. , Santos I. D. R. dos , Oliveski R. D. C.
Published: November 2018

The demand for renewable energy resources and the need for the development of components which increase how it collects, transforms, stores and distributes this energy, emphasizes the importance of improving current technological systems to meet these demands. Phase change materials (PCM) offer great potential in this area. as they can increase energy efficiency in thermal systems as well as save energy by storing solar energy or waste heat from industrial processes, which is made possible by the high amount of energy stored per mass and volume unit, with low temperature variation. Therefore, it is of high importance that the suggested mathematical and numerical models are capable of analyzing its energy performance. The present work uses a mathematical and numerical model of Computational Fluid Dynamics (CFD), capable of reproducing the solidification process of erythritol in spheres of 10, 20, 30 and 40 mm diameters, with temperature differences of 10, 15, 20, 25, 30 and 40 K between the sphere wall and the phase change temperature of the material. The problem is considered two- dimensional and transient. The model consists of mass, energy, momentum and volume fraction equations. The mathematical and numerical model is validated with experimental results from the literature, presenting good agreement between them. After space and time discretization tests, we analyze liquid fraction over time and heat flux at the sphere wall. The results show that liquid fraction suffers a strong reduction in the beginning of the solidification process due to the high heat flux in the early stages. As the solid layer near the wall increases, it causes an increase in thermal resistance, causing a significant reduction in heat flux.
ESTIMATING SURFACE VELOCITIES IN THE SOUTHERN BRAZILIAN AND URUGUAYAN CONTINENTAL SHELVES USING THE MAXIMUM CROSS-CORRELATION METHOD
Authors: Costi J. , Kirinus E. P. , Marques W. C. , Garcia C. A. E. , Fujita C.
Published: November 2018

The present study investigates the viability of using the maximum cross- correlation method on ocean color imagery to estimate surface velocities on the Southern Brazilian and Uruguayan continental shelf. The method searches for maximum correlation areas in two sequential images, determining the displacement of oceanographic features within the time interval of the images acquisition. We use the NWL550 parameter of MODIS-Aqua imagery, once it is well correlated with the total suspended matter in the water and provides relatively well-defined optical features on the Southern Brazilian and Uruguayan continental shelves. The estimated velocity fields showed a preferential direction northward, with average intensities between 0.06 m/s and 0.11 m/s. The frequent cloud coverage and the diffusive processes restrict the number of image pairs suitable for the analysis. Nevertheless, the method showed potential for investigating the current velocity fields on the study area, as the estimates are in agreement with the wind fields and the velocities' intensities are well within the values previously described in the literature for the region.
OPTIMIZATION TO INCREASE ENERGY EFFICIENCY OF A SIROCCO CENTRIFUGAL FAN USING COMPUTATIONAL FLUID DYNAMICS (CFD)
Authors: Kothe L. B. , Petry A. P. , Vecina T. D. J. , Luz J. L. R.
Published: November 2018

This paper presents a numerical and experimental study on the aerodynamic performance of Sirocco centrifugal fans seeking an increase in energy efficiency. Numerical simulations are performed by the Finite-Volume Method commercial code ANSYS Fluent. Characteristics such as flow rate at the outlet, consumed power and sound pressure levels emitted by centrifugal fans with the original model of 16 blades and the optimized models of 16 and 14 blades are compared. Numerical calculations are performed by the continuity equation, the Reynolds Averaged Navier- Stokes (RANS) equations and the k-ω SST turbulence model. The quality of the mesh is evaluated for three different mesh densities. Results demonstrate that it was possible to obtain an increase of flow rate up to 22.7%, and reductions in the noise levels without increasing the consumption of the electric motor.
NUMERICAL STUDY OF A TRIANGULAR FIN INSERTED IN A SQUARE CAVITY WITH UPPER SLIDING SURFACE SUBJECTED TO A MIXED CONVECTION EFFECT
Authors: Razera A. L. , Fagundes T. M. , Fonseca R. J. C. , Lessa L. Z. , Schmidt A. , Furtado G. M. , Santos E. D. , Isoldi L. A. , Rocha L. A.
Published: November 2018

This article investigates numerically, using the Constructal Design method, a system that combines a square cavity with upper sliding wall and a triangular fin subjected to the mixed convection effect. The objectives are to evaluate the influence of the fin aspect ratio (H1/L1) on the average Nusselt number on the fin surface and to analyze the effect of the fraction of the area of the triangular fin relative to the square cavity (φ). The proposed problem is assumed two-dimensional, laminar, incompressible and steady flows. For the buoyancy forces it is considered the Boussinesq approximation. In order to generalize the results, the problem is solved in dimensionless form. The fluid flowing through the cavity presents the thermophysical properties defined by the Prandtl number (Pr = 0.71). The buoyancy force in the flow is defined by the Rayleigh number (RaH = 104), while the flow regime is governed by the Reynolds number (ReH = 102). The optimum fin geometry that maximizes the heat transfer between the finned cavity and the surrounding fluid is obtained through the Constructal Design method. The numerical solution of the conservation equations of mass, momentum and energy is calculated with the finite volume method, using the commercial fluid dynamics software FLUENT®. The geometry and mesh computational domain were developed in GAMBIT® package. As results, it was found that the optimal configurations of H1/L1 presented a gain in the thermal performance of up to 15% in relation to the other geometries. In addition, the heat transfer has great dependence on the variation of the fraction of area (φ).
GEOMETRIC EVALUATION OF T AND H-SHAPED CAVITIES INSERTED IN A SOLID WITH HEAT GENERATION APPLYING CONSTRUCTAL DESIGN
Authors: Teixeira F. B. , Pereira M. S. , Feijó B. C. , Rocha L. A. O. , Isoldi L. A. , Santos E. D.
Published: November 2018

In this work, the influence of geometry on the behavior of the temperature field in a square plate with T and H-shaped cavities is studied. The ratio between the cavity area and the plate area will be kept constant and its geometry will be varied in order to find the optimum geometry (the one that results in the temperature field with the lowest maximum temperature). The cavity will occupy 10% of the area of the plate and will be varied from the T-shaped configuration to the H-shaped one. According to the Constructal Design principles, the degrees of freedom of the problem and its restrictions will be defined. The height of the initial T was selected as H1, where H1/L1 is one of the degrees of freedom for the problem. The second degree of freedom is the ratio H2/L2, the ratio of height by the width of the first bifurcation, and the other geometric ratio (H3/L3) is the ratio of height by the width of the second bifurcation and is a function of H1. For the simulations, a code based on the Finite Element Method (FEM) was used to solve the energy conservation equation. The results showed that it is possible to minimize the maximum excess temperature by 54.4% when an H-shaped geometry with irregular legs is used compared with the T-shaped cavity. In order to reach the optimum geometry, H1/L1 was reduced by 68.37%, and H2/L2 was increased in 64.71% when compared to the initially proposed T-shaped cavity.
NUMERICAL ANALYSES OF OPENFOAM'S OVERTOPPING DEVICE SOLUTION
Authors: Barbosa D. V . E. , Souza J. A. , Santos E. D. dos , Isoldi L. A. , Martins J. C.
Published: November 2018

Studies related to ocean energy are getting more important lately, once world claims for renewable energy usage. The Overtopping Device is a kind of Ocean Waves Energy Converter (OWEC), which main concept is storing water provided by incident waves above sea level to feed a set of low head turbines. In order to obtain the desired effect, this device contains a ramp which elevates the incident waves toward the reservoir. Present study aims to perform a numerical model of a 2D Overtopping Device by means of OpenFOAM simulations. OpenFOAM is a free open source code which has shown applicability in many areas of engineering. The adopted solver (InterFOAM) is Volume of Fluid based (VOF) according to Finite Volume Method (FVM), these methodologies has been largely used among researchers in propagating waves field. FLUENT (commercial code) is used to verify OpenFOAM's results. Once, the main point of this paper is to present OpenFOAM as a considerable tool for propagating waves studies, it firstly presents a numerical wave verification with analytical solutions (second order Stokes theory). The second section of results presents overtopping time series peaks in 100 s of simulation. Also, by mass flow rate integration, it presents total mas of water climbed to the reservoir. The integration of mass flow rate takes 94 s of simulation (not 100 s) because it is noticeable a pause between two peaks of overtopping at that time. Results show agreement between wave elevation and wave velocity profiles with straight convergence of periods between analytical and numerical waves. Most important differences are found near air/water interface, owed to faster air flow at that region. Generally OpenFOAM and FLUENT results are similar, with converged overtopping time series peaks and their magnitudes too. Similarly, the amount of water marked by both software are close with very similar trend lines.
ANALYSIS OF A COMBINED BRAYTON/RANKINE CYCLE WITH TWO REGENERATORS IN PARALLEL
Authors: Santos J. T. dos , Fagundes T. M. , Santos E. D. dos , Isoldi L. A. , Rocha L. A. O.
Published: November 2018

This work presents a configuration of two regenerators in parallel for a power generation Brayton/Rankine cycle where the output power is 10 MW. The working fluids considered for the Brayton and Rankine cycles are air and water, respectively. The addition of a regenerator with the previous existing cycle of this kind resulted in the addition of a second-stage turbine in the Rankine cycle of reheat. The objective of this modification is to increase the thermal efficiency of the combined cycle. In order to examine the efficiency of the new configuration, it is performed a thermodynamic modelling and numerical simulations for both cases: a regular Brayton/Rankine cycle and the one with the proposed changes. At the end of the simulations, the two cycles are compared, and it is seen that the new configuration reaches a 0.9% higher efficiency. In addition, the vapor quality at the exit of the higher turbine is higher, reducing the required mass flow rate in 14%.
WARNING SYSTEM FOR NAVIGATION AND MOORED SHIPS IN PORTS
Authors: Pinheiro L. V. , Fortes C. J. , Lopes P. , Poseiro P. , Santos J. A.
Published: November 2018

This paper describes the SWAMS ALERT system; a forecast and warning system based on the assessment of risks associated with navigation and moored ships in port areas. This system is based on HIDRALERTA, a previously developed system for overtopping and flooding in coastal and port areas. The basic idea is to use 72-hour sea waves’ forecasts and simulate their effect on ships, either in port approach maneuvers or when they are moored inside.This modular system consists of four modules: I – Sea waves characteristics; II - Navigation and mooring in port areas; III - Risk assessment and IV - Warning System. The system is implemented on a fully interactive user-friendly web platform.The system prototype was tested in the Azorean island of Terceira. A generic container ship and a specific berth in the container terminal of the Praia da Vitória port were chosen, as well as a generic mooring layout with six mooring cables and two fenders. This test case illustrates some of the system’s capabilities, namely its ability to forecast, not only wave characteristics on the specific site of the moored vessel, but also forces on mooring lines and fenders and the risk of pre-set thresholds being surpassed.
STOCHASTIC OPTIMIZATION OF MULTIPLEX CHARGES BASED ON INTERIOR BALLISTICS SIMULATIONS
Authors: Caldeira A. B. , Cury T. L. B. , Rezende A. L. T. , Gomes A. V.
Published: November 2018

Multiplex charges combine propellant grains with regressive, neutral and progressive burning behaviors in a single propellant charge to improve the interior ballistics. This work optimizes the mass and the web thickness of each type of propellant grain used in a multiplex charge. Two optimization problems are studied: the maximization of the muzzle velocity and the minimization of the maximum pressure inside the gun. Particle Swarm Optimization (PSO) and Differential Evolution (DE) were used to solve the optimization problems. The interior ballistics of a 155 mm howitzer was simulated by using a lumped parameters model. In this model, the lost energy and the resistance pressure are defined by spline functions based on reference data. The results show that optimized multiplex charges can be used to increase the weapon’s utility range and to reduce the weapon’s weight.
FORECAST STRUCTURE DEVELOPMENT FOR MODELLING THE SOUTHERN BRAZILIAN CONTINENTAL SHELF HYDRODYNAMIC
Authors: Stringari C. E. , Kirinus E. P. , Costi J. , Oleinik P. H. , Marques W. C.
Published: November 2018

Global forecast models have been widely used worldwide; however, they lack ability to prescribe high quality local data. In this paper, an assembly of oceanographic (RTOFS) and atmospheric (GFS) global data base are used to set up a nested forecast system. The approach proposed relies on the  sage of python and FORTRAN scripts to download and assemble global metocean data, in addition to interpolate it towards the study area numerical grid as boundary conditions. Therefore, the TELEMAC-3D hydrodynamic model is automatically initiated in order to provide the regional forecast for the Southern Brazilian Continental Shelf. Results shows that the methodology proposed represent properly the flow dynamics inside the Patos Lagoon and also in the Tramandaí beach, with low/high frequency dynamic effects and influences being reported.
A LOCAL DIFFERENTIAL QUADRATURE METHOD WITH VARIABLE SHAPE MULTIQUADRICS: TESTS ON POISSON EQUATION AND FLUID DYNAMICS USING CONSISTENT CLOUD REFINEMENTS
Authors: Silva J. R. da , Santos L. G. C. , Manzanares Filho N.
Published: November 2018

A meshless Local Differential Quadrature Method for solving partial differential equations is presented in this paper. It is based in a point cloud discretization and local supports. A basis set of Multiquadric functions is employed for determining the weight coefficients in derivative approximations. Tests with the Poisson equation are presented for verifying the converge behavior of the method in Clouds with Unstructured Generation (CUG’s). A consistent refinement procedure for varying the multiquadric shape parameter between local supports is proposed. The method is finally applied for solving the classical benchmark problem of natural convection in a square cavity. Satisfactory results were obtained in comparison with the reference literature.
PERFORMANCE ANALYSIS OF ALTERNATIVE COVERINGS FOR COOLING TOWERS IN BRAZILIAN CAPITALS THROUGH NUMERICAL MODELING
Authors: Tomás A. C. C. , Souza P. H. , Primo A. R. M.
Published: November 2018

A cooling tower is a heat removal device used to transfer waste heat to the atmosphere process. Today, commercial cooling towers use plastic coverings, specially developed for this application. It is known that alternative coverings have been an increasingly viable solution thanks to its performance and cost. The purpose of this study was to evaluate, through numerical simulation, the performance of different alternative coverings under different climatic conditions. Therefore, we used, as reference, the climate of the state capitals and their respective geographic regions. The performance of these coverings was evaluated through observation of three parameters: effectiveness, approach and cooling. The main input data used by the software EES (Engineering Equation Solver) for the calculation of evaluation parameters were: experimental NUT of each covering, average local temperature, local air pressure and relative humidity. The flow of water and air were set at 0.33 L / s and 170 L / s, respectively. We concluded that the air inlet temperature and relative humidity at each location greatly influence the performance of the coverings. The alternative covering that showed the best results was the "cross-fiber and neck", with an efficiency about 35% lower than the industrial covering. The Brazilian capital city with the best performances for alternative coverings was Palmas (TO). This is due to the very low relative humidity found in the city in the summer. Air humidity is also responsible for the poor performance of coverings in the capitals of the North. In general, the region with the best performance was the South, due to the characteristics of the sub-tropical climate. Regions that had the worst results were North / Northeast because of the weather that combines high temperatures with high / moderate humidity, respectively. Thus, the study of climate conditions is indispensable for the operation prevision of a cooling tower. Alternative coverings will be viable depending on the location.