A novel parallel block-based anisotropic adaptive mesh refinement (AMR) technique for multi-block body-fitted grids is proposed and described. Rather than adopting the more usual isotropic approach to mesh refinement, an anisotropic refinement procedure is proposed which allows refinement of grid blocks in each coordinate direction in an independent fashion. This allows for more efficient and accurate treatment of narrow layers and/or discontinuities which occur, for example, in the boundary and mixing layers of viscous flows, and in regions of strong non-linear wave interactions with shocks. The anisotropic AMR technique is implemented within an existing finite-volume framework, which encompasses both explicit and implicit solution methods, and is capable of performing calculations with second- and higher-order spatial accuracy. To clearly demonstrate the feasibility of the proposed technique, it is applied to the unsteady and steady-state solutions of both the advection diffusion equation, as well as the Euler equations, in two space dimensions.

A novel parallel block-based anisotropic adaptive mesh refinement (AMR) technique for multi-block body-fitted grids is proposed and described. Rather than adopting the more usual isotropic approach to mesh refinement, an anisotropic refinement procedure is proposed which allows refinement of grid blocks in each coordinate direction in an independent fashion. This allows for more efficient and accurate treatment of narrow layers and/or discontinuities which occur, for example, in the boundary and mixing layers of viscous flows, and in regions of strong non-linear wave interactions with shocks. The anisotropic AMR technique is implemented within an existing finite-volume framework, which encompasses both explicit and implicit solution methods, and is capable of performing calculations with second- and higher-order spatial accuracy. To clearly demonstrate the feasibility of the proposed technique, it is applied to the unsteady and steady-state solutions of both the advection diffusion equation, as well as the Euler equations, in two space dimensions.

Forging is a manufacturing process which is preferred among the others in that, the final product shows more enhanced properties. The properties of the final product are directly related with the material used in the forging process. Main parameters such as forging temperature, number of stages, preform design, dimensions of the billet, etc. may be affected by the forging material. Alloys are one of the main areas of interest in the forging industry. The use of alloy steels may bring superior properties, especially in terms of strength and forgeability. In this study, three different alloy steels, which are hot forged in industry have been examined. The flow of the material, stress distribution, die filling and the effects of the process parameters on the forging have been investigated. Three industrial forging parts / M20 and M30 eye bolts and a runner block have been studied. Finite Volume Analysis of the forging process has been performed for carbon steels / C45 and C60 and alloy steels / a stainless steel X20Cr13, a heattreatable alloy steel, 42CrMo4 and a bearing steel, 100Cr6. The results of the simulations have been compared with the findings of the experiments carried out in a forging company. It has been observed that numerical and experimental results are in good agreement.

The performance prediction of solid propellant rocket motor depends on the calculation of internal aerodynamics of the motor through its operational life. In order to obtain the control volume, in which the solutions will be carried out, a process called &ldquo / grain burnback calculation&rdquo / is required. During the operation of the motor, as the interface between the solid and gas phases moves towards the solid propellant in a direction normal to the surface, the combustion products are generated and added into the control volume. This phenomenon requires handling of moving boundaries as the solution proceeds. In this thesis, Fast Marching Method is implemented to the problem of grain burnback. This method uses the upwinding nature of the propellant interface motion and solves the Eikonal type equations on a fixed three-dimensional tetrahedron mesh. The control volume is coupled to a one-dimensional and a three-dimensional Euler aerodynamic solver in order to obtain the performance of the engine. The speed by which the interface moves depends on the static pressure on the surface of the propellant and comes from the solver. Therefore an iterative method has been proposed between the interface capturing algorithms and the flow solver. Both of the calculation results, which are obtained from one-dimensional and three-dimensional solvers are compared with actual rocket firing data and validated.

WEAR ANALYSIS OF HOT FORGING DIES ABACHI, Siamak M. S., Department of Mechanical Engineering Supervisor: Prof. Dr. Metin AKK&Ouml / K Co-Supervisor: Prof. Dr. Mustafa lhan G&Ouml / KLER December 2004, 94 pages The service lives of dies in forging processes are to a large extent limited by wear, fatigue fracture and plastic deformation, etc. In hot forging processes, wear is the predominant factor in the operating lives of dies. In this study, the wear analysis of a closed die at the final stage of a hot forging process has been realized. The preform geometry of the part to be forged was measured by Coordinate Measuring Machine (CMM), and the CAD model of the die and the worn die were provided by the particular forging company. The hot forging operation was carried out at a workpiece temperature of 1100&deg / C and die temperature of 300&deg / C for a batch of 678 on a 1600-ton mechanical press. The die and the workpiece materials were AISI L6 tool steel and DIN 1.4021, respectively. The simulation of forging process for the die and the workpiece was carried out by Finite Volume Method using MSC.SuperForge. The flow of the material in the die, die filling, contact pressure distribution, sliding velocities and temperature distribution of the die have been investigated. In a single stroke, the depth of wear was evaluated using Archard&rsquo / s wear equation with a constant wear coefficient of 1&yen / 10-12 Pa-1 as an initial value. The depth of wear on the die surface in every step has been evaluated using the Finite Volume simulation results and then the total depth of wear was determined. To be able to compare the wear analysis results with the experimental worn die, the surface measurement of the worn die has been done on CMM. By comparing the numerical results of the die wear analysis with the worn die measurement, the dimensional wear coefficient has been evaluated for different points of the die surface and finally a value of dimensional wear coefficient is suggested. As a result, the wear coefficient was evaluated as 6.5&yen / 10-13 Pa-1 and considered as a good approximation to obtain the wear depth and the die life in hot forging processes under similar conditions.

An unstructured explicit, Reynolds averaged Navier-Stokes solver is developed to operate on inviscid flows, laminar flows and turbulent flows and one equation Spalart-Allmaras turbulence modeling is implemented to the solver. A finite volume formulation, which is cell-center based, is used for numerical discretization of Navier-Stokes equations in conservative form. This formulation is combined with one-step, explicit time marching upwind numerical scheme that is the first order accurate in space. Turbulent viscosity is calculated by using one equation Spalart-Allmaras turbulence transport equation. In order to increase the convergence of the solver local time stepping technique is applied. Eight test cases are used to validate the developed solver,for inviscid flows, laminar flows and turbulent flows. All flow regimes are tested on NACA-0012 airfoil. The results of NACA-0012 are compared with the numerical and experimental data.

The aim of this study is to simulate the unsteady flow around rotating or oscillating airfoils. This will help to understand the rotor aerodynamics, which is essential in turbines and propellers. In this study, a pre-existing Euler solver with finite volume method that is developed in the Mechanical Engineering Department of Middle East Technical University (METU) is improved. This structured pre-existing code was developed for 2-D internal flows with Lax-Wendroff scheme. The improvement consist of firstly, the generalization of the code to external flow / secondly, implementation of first order Roe&rsquo / s flux splitting scheme and lastly, the implementation of rotation with the help of Arbitrary Lagrangian Eulerian (ALE) method. For the verification of steady and unsteady results of the code, the experimental and computational results from literature are utilized. For steady conditions, subsonic and transonic cases are investigated with different angle of attacks. For the verification of unsteady results of the code, oscillating airfoil case is used. The flow is assumed as inviscid, unsteady, adiabatic and two dimensional. The gravity is neglected and the air is taken as ideal gas. The developed code is run on computers housed in METU Mechanical Engineering Department Computational Fluid Dynamics High Performance Computing (CFD-HPC) Laboratory.

Forging is a metal forming process commonly used in industry. Forging process is strongly affected by the process temperature. In hot forging process, a wide range of materials can be used and even complex geometries can be formed. However in cold forging, only low carbon steels as ferrous material with simple geometries can be forged and high capacity forging machinery is required. Warm forging compromise the advantages and disadvantages of hot and cold forging processes. In warm forging process, a product having better tolerances can be produced compared to hot forging process and a large range of materials can be forged compared to cold forging process. In this study, forging of a particular part which is being produced by hot forging at 1200&deg / C for automotive industry and have been made of 1020 carbon steel, is analyzed by the finite volume analysis software for a temperature range of 850-1200&deg / C. Experimental study has been conducted for the same temperature range in a forging company. A good agreement for the results has been observed.

Submitted by Josirene Barbosa (josirene.henrique@ufcg.edu.br) on 2018-01-22T14:06:12Z No. of bitstreams: 1 BRAUNER GONÇALVES COUTINHO - TESE PPGEP 2013.pdf: 5662839 bytes, checksum: 38e4233d72065d1a5e3baa86c6f3f108 (MD5) / Made available in DSpace on 2018-01-22T14:06:12Z (GMT). No. of bitstreams: 1 BRAUNER GONÇALVES COUTINHO - TESE PPGEP 2013.pdf: 5662839 bytes, checksum: 38e4233d72065d1a5e3baa86c6f3f108 (MD5) Previous issue date: 2013-08-29 / CNPq / O processo RTM é amplamente utilizado para a produção de materiais compósitos de alta qualidade. As simulações computacionais podem desempenhar um importante papel na otimização deste processo, reduzindo custos e tornando-o mais eficiente. Neste trabalho, foi desenvolvida uma modelagem matemática bidimensional transiente para a etapa de preenchimento do molde em processos RTM que prediz o escoamento de duas fases (ar-resina) em meios porosos. O conjunto de equações diferenciais parciais, escritas em coordenadas generalizadas, é discretizado utilizando o método de volumes finitos e resolvido por meio de uma abordagem totalmente implícita via método de Newton com um esquema de passo de tempo variável. Foi desenvolvido um simulador computacional com ferramentas de pré e pós-processamento para ajudar na definição de parâmetros de simulações e na visualização dos resultados obtidos. Para validar a metodologia matemática proposta, resultados numéricos de tempo de preenchimento, posição da frente de fluxo, pressão e vazão de injeção para escoamentos radiais e retilíneos foram comparados com resultados analíticos conhecidos. Como aplicação, o modelo foi usado para descrever o escoamento de óleo vegetal em uma pré-forma de fibra de vidro no interior de uma cavidade retangular e os resultados comparados com dados oriundos de estudos experimentais. Também foram simulados casos envolvendo fronteiras irregulares arbitrárias. O modelo proposto e o simulador mostraram-se consistentes produzindo resultados fisicamente coerentes para as variáveis do processo. / The RTM process is widely used for the production of high quality composite materials. Computer simulations can play an important role in the optimization of this process, reducing costs and increasing efficiency. In this work, it was developed a 2D transient mathematical model for the mold filling stage in RTM process which predicts the twophase flow (air-resin) through porous media. The set of partial differential equations, written in boundary fitted coordinates, is discretized using the finite volume method in a fully implicit approach and solved by using the Newton’s method. It was developed a computational simulator with pre- and post-processing tools to help the definition of simulations parameters and the visualization of the results. To validate the mathematical methodology, numerical results for filling time, flow front position, injection pressure and injection flow rate for rectilinear and radial flows were compared to analytical results from known models. The model was employed to describe the fluid flow of a vegetable oil in a glass fiber preform within a rectangular cavity and the results were compared to experimental data. Some cases involving arbitrary irregular boundaries were also simulated. The proposed model and the simulator generated physically consistent results of the process variables.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Uma análise utilizando a série de Taylor é apresentada para se estimar a priori os erros envolvidos na solução numérica da equação de advecção unidimensional com termo fonte, através do Método dos Volumes Finitos em uma malha do tipo uniforme e uma malha não uniforme. Também faz-se um estudo a posteriori para verificar a magnitude do erro de discretização e corroborar os resultados obtidos através da análise a priori. Por meio da técnica de solução manufaturada tem-se uma solução analítica para o problema, a qual facilita a análise dos resultados numéricos encontrados, e estuda-se ainda a influência das funções de interpolação UDS e CDS e do parâmetro u na solução numérica. / An analysis based on Taylor series is presented for estimating a priori the errors involved in the numerical solution of advection equation one-dimensional with source term, using the Finite Volume Method in a mesh uniform and a nonuniform mesh. Also is accomplished a study to determine the magnitude of discretization error and corroborate the results obtained on analyzing a priori. By using the technique of solution manufactured is produced an analytical solution for the problem, which facilitates analysis of the numeric results, and was also studied the influence functions of interpolation UDS and CDS and of parameter u in the numerical solution.