CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / à corrente o uso de inspeÃÃo nÃo-destrutiva ultrassÃnica na detecÃÃo de descontinuidades nos mais diversos materiais utilizados na indÃstria Adicionalmente informaÃÃes sobre a microestrutura do material inspecionado podem ser obtidas a partir do processamento da sÃrie temporal produzida durante a inspeÃÃo A simulaÃÃo do ensaio ultrassÃnico representa uma importante ferramenta para o entendimento e previsÃo da interaÃÃo da onda mecÃnica com o meio No entanto faz-se necessÃrio primeiramente modelar o meio que reproduza as caracterÃsticas de uma amostra objeto de estudo por onde a onda propaga Cinco meios unidimensionais compostos por domÃnios (representando grÃos) com tamanho mÃdio distinto e a mesma densidade mÃdia foram definidos neste trabalho SimulaÃÃes de propagaÃÃo de ondas ultrassÃnicas nos meios modelados foram executadas para quatro diferentes frequÃncias de ondas Concomitantemente foram capturados sinais ultrassÃnicos sobre cinco amostras de aÃo contendo diferentes tamanhos mÃdios de grÃo utilizando transdutores de 2.25 5.0 10.0 e 20.0 MHz Todos os sinais obtidos foram submetidos à detrended fluctuation analysis DFA e rescaled range analysis R/S duas tÃcnicas de anÃlise de flutuaÃÃes em sÃries temporais com vista a filtrar informaÃÃes espÃrias e avaliar influÃncia das variÃveis selecionadas (tamanho de grÃo e frequÃncia do sinal) sobre os sinais ultrassÃnicos obtidos Por fim à feita uma comparaÃÃo entre os dados simulados e experimentais e avaliaÃÃo da qualidade da simulaÃÃo / It is usual the application of ultrasonic non-destructive evaluation to detect discontinuities in different materials applied in industry Furthermore information about the microstructure of the inspected material can be obtained by signal processing of time series produced during the inspection Simulation of ultrasonic testing can be an important tool to help the understanding and predicting the interaction of mechanical wave in materials First of all computational materials modeling to reproduce the characteristics of specimens through which the wave propagates is necessary Five different one-dimensional materials composed of domains (grains) with different average size and same density were designed in this work Simulations of ultrasonic wave propagation in the modeled materials were performed at four different wave frequencies Concomitantly ultrasonic signals were acquired from five steel samples containing different average grain sizes using probes with central frequency of 225 5 10 and 20 MHz Detrended fluctuation analysis DFA and rescaled range analysis R/S two techniques for analyzing fluctuations in time series were used to process the signals in order to filter out spurious information and evaluate the influence of selected variables (grain size and frequency of the signal) on the ultrasonic signals obtained Finally simulated and experimental data and compared in order to evaluate the simulation performance

In this thesis study, Detached Eddy Simulation turbulence model is studied in two dimension mainly for flow over single element airfoils in high Reynolds numbers to gain experience with model before applying it to a three dimensional simulations. For this aim, Spalart-Allmaras and standard DES ,DES97, turbulence models are implemented to parallel, viscous, hybrid grid flow solver. The flow solver ,Set2d, is written in FORTRAN language. The Navier-Stokes equations are discretized by first order accurately cell centered finite volume method and solved explicitly by using Runge-Kutta dual time integration technique. Inviscid fluxes are computed using Roe flux difference splitting method. The numerical simulations are performed in parallel environment using domain decomposition and PVM library routines for inter-process communications. To take into account the effect of unsteadyness after the convergence is ensured by local time stepping technique for four order magnitude drop in density residual, global time stepping is applied for 20000 iterations. The solution algorithm is validated aganist the numerical and experimental studies for single element airfoils in subsonic and transonic flows. It is seen that Spalart-Allmaras and DES97 turbulence models give the same results in the non-seperated flows. Grey area is investigated by changing $C_{DES}$ coefficient. Modeled Stress Depletion which cause reduction of eddy viscosity is observed.