Método de otimização e técnica de modelagem de interface para análise do escoamento em difusores radiais com geometrias irregulares

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Mecânica.Neste trabalho uma metodologia híbrida euleriana-lagrangeana é utilizada para simular escoamentos viscosos, incompressíveis em geometrias irregulares entre fluido e sólido. A metodologia é validada na resolução do escoamento em cavidades com topo deslizante e bases irregulares. Resultados experimentais e numéricos para difusores radiais com alimentação axial são utilizados na validação do código computacional desenvolvido no presente trabalho. Na seqüência esta metodologia é utilizada para investigar a influência no escoamento de alterações geométricas introduzidas em válvulas automáticas de compressores herméticos. A busca da geometria ótima é feita através do método de pontos interiores de Herskovits

Resolução de sistemas lineares gerados na discretização das equções de Navier-Stokes em malhas de voronoi

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoEsta dissertação descreve, analisa e implementa métodos iterativos da família do Gradiente Conjugado (GC), na solução de sistemas lineares resultantes da discretização das equações de Navier-Stokes (NS) e da equação da condução de calor em malhas não-estruturadas de Voronoi, utilizando o método dos volumes finitos. Descreve-se e adota-se três tipos de ordenações na malha computacional, avaliando o desempenho através de métodos iterativos. Apresenta-se algumas técnicas de pré-condicionamento e implementa-se três delas: diagonal, SSOR e por fatoração de Cholesky incompleta. Estas, aplicadas no método GC e analisadas de acordo com a distribuição dos autovalores. Na discretização das equações de NS são utilizadas três formas distintas de avaliação dos gradientes de pressão, validados no cálculo do escoamento laminar incompressível

NUMERICAL STUDIES OF NATURAL CONVECTION IN A SQUARE CAVITY

In the present work a numeric study of thermal and fluid dynamics behavior of natural air convection in a bi-dimensional square cavity is presented, in a laminar flow. The square cavity has two walls heated with different temperatures and two isolated walls, the Boussinesq approximation is used and a constant Prandtl number. The Finite Volume Method is used for the discretization of flow equations. The staggered load of variables is adopted and Power-Law and SIMPLE models are used. The numeric simulation is made up of several Rayleigh numbers, 104 Ra 106, and the results of average Nusselt numbers are compared to values obtained in the literature. Flow and isotherm lines are presented and analyzed. The numerical results presented here in this work agree with the ones available in the literature and can be used by researchers who work in the convection problem numeric simulation area

Natural convection in a partially open square cavity with internal heat source: An analysis of the opening mass flow

AbstractA steady buoyancy-driven flow of air in a partially open square 2D cavity with internal heat source, adiabatic bottom and top walls, and vertical walls maintained at different constant temperatures is investigated numerically in this work. A heat source with 1% of the cavity volume is present in the center of the bottom wall. The cold right wall contains a partial opening occupying 25%, 50% or 75% of the wall. The influence of the temperature gradient between the verticals walls was analyzed for Rae=103–105, while the influence of the heat source was evaluated through the relation R=Rai/Rae, investigated at between 400 and 2000. Interesting results were obtained. For a low Rayleigh number, it is found that the isotherm plots are smooth and follow a parabolic shape indicating the dominance of the heat source. But as the Rae increases, the flow slowly becomes dominated by the temperature difference between the walls. It is also observed that multiple strong secondary circulations are formed for fluids with a small Rae whereas these features are absent at higher Rae. The comprehensive analysis is concluded with horizontal air velocity and temperature plots for the opening. The numerical results show a significant influence of the opening on the heat transfer in the cavity

Aggregating Prophet and Seasonal Trend Decomposition for Time Series Forecasting of Italian Electricity Spot Prices

The cost of electricity and gas has a direct influence on the everyday routines of people who rely on these resources to keep their businesses running. However, the value of electricity is strongly related to spot market prices, and the arrival of winter and increased energy use owing to the demand for heating can lead to an increase in energy prices. Approaches to forecasting energy costs have been used in recent years; however, existing models are not yet robust enough due to competition, seasonal changes, and other variables. More effective modeling and forecasting approaches are required to assist investors in planning their bidding strategies and regulators in ensuring the security and stability of energy markets. In the literature, there is considerable interest in building better pricing modeling and forecasting frameworks to meet these difficulties. In this context, this work proposes combining seasonal and trend decomposition utilizing LOESS (locally estimated scatterplot smoothing) and Facebook Prophet methodologies to perform a more accurate and resilient time series analysis of Italian electricity spot prices. This can assist in enhancing projections and better understanding the variables driving the data, while also including additional information such as holidays and special events. The combination of approaches improves forecast accuracy while lowering the mean absolute percentage error (MAPE) performance metric by 18% compared to the baseline model

Study of ceilingdeflector application in a poultry house

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.This present work proposes to apply the Computational Fluid Dynamics (CFD) by using Ansys® CFX version 14.5 to evaluate the impact of roof deflectors on the airflow patterns inside a tunnel ventilation poultry building located at Montenegro city (Brazil). Four different cases have been considered: roof with 24° of inclination with and without deflectors, with 6° of inclination and ceiling without inclination. For each case, it has generated three meshes (coarse, intermediate and fine) by using ICEM CFD 14.5 verifying mesh quality by aspect ratio and y+, and the verification has done by comparing velocity and temperature profiles. It was used the k-ε standard turbulent model and Reynolds number at inlet is above 105, isothermal walls, null relative pressure at outlets and variation velocity at inlet according pressure drop. Results obtained show the higher pressure drop at roof with 24° of inclination with deflector.am201

Chaotic coyote algorithm applied to truss optimization problems

The optimization of truss structures is a complex computing problem with many local minima, while metaheuristics are naturally suited to deal with multimodal problems without the need of gradient information. The Coyote Optimization Algorithm (COA) is a population-based nature-inspired metaheuristic of the swarm intelligence field for global optimization that considers the social relations of the coyote proposed to single-objective optimization. Unlike most widespread algorithms, its population is subdivided in packs and the internal social influences are designed. The COA requires a few control hyperparameters including the number of packs, the population size, and the number maximum of generations. In this paper, a modified COA (MCOA) approach based on chaotic sequences generated by Tinkerbell map to scatter and association probabilities tuning and an adaptive procedure of updating parameters related to social condition is proposed. It is then validated by four benchmark problems of structures optimization including planar 52-bar truss, spatial 72-bar truss, 120-bar dome truss and planar 200 bar-truss with discrete design variables and focus in minimization of the structure weight under the required constraints. Simulation results collected in the mentioned problems demonstrate that the proposed MCOA presented competitive solutions when compared with other state-of-the-art metaheuristic algorithms in terms of results quality