Background: Since three decade ago, the application of the concept of finite element analysis (EEA) have received a keen interest among dental investigators. In practice the FEA provides detailed stress information regarding to a non-homogenious body such as craniofocal skeletal growth, tooth post ceramo-metal crowns and etc. The aim of this study was the determination of the influence of stress distribution at the cement interface of metal ceramic restoration-dentin. Materials and Methods: An idealized metal-ceramic crown model was developed. The model was divided into very small segments. Various loading conditions was applied to the model. A super sap software was used for analyzing the stress distribution. Results & Conclusion: The results of this study suggest that the higher shear stress was developed in the cervical region by two dimensional methods.

Compound channels are consisting of two hydraulic sections namely main channel and floodplain. In meandering rivers, with the passage of time and lateral movement of the meanders, the external bending progression and the sinusoidal or curvature is increased. The curvature of meandering sections can be defined by a dimensionless parameter as the sinusoidal number which is the ratio of meandering length of main channel to the floodplain length. In this research work, the hydraulic characteristics of flow including the velocity magnitude, boundary shear stress, turbulence intensity and turbulence energy of the main channel along the meandering compound channel have been investigated numerically, regarding changes in the sinusoidal ratio for six types of channels with different sinusoidal ratios. In order to investigate the effect of sinusoidal ratio in meandering compound channels on the hydraulic characteristics of the flow, the FLOW3D software is applied. Numerical simulation results show that by increasing the channel sinusoidal number from 1 to 1. 641, the velocity and bed shear stress decrease and the turbulence intensity and energy increases. So that the maximum value of the above parameters occurs in the inner arc.

In this work, the asymptotic equilibrium behaviour of dimensionless parameters in stably stratified turbulence submitted to a horizontal shear is studied using two different methods. The first one is an analytic method and is based on linear solutions obtained when non linear effects of pressure and viscosity are neglected. The Laplace Transform is used for integrating differential system. The principal result of this first part of our work is the existence of asymptotic equilibrium states at high shear for all non dimensionless parameters. The second method is a numerical one and is based on a second-order modeling of equations. The Speziale Sarkar and Gatski (SSG) model is retained for pressure-strain correlation and dissipation time evolution equation, whereas, three of the most known second-order models are retained for the scalar field. The principal result of this second part is the big contribution of the SSG models for predicting asymptotic equilibrium states of non dimensional parameters.

In this paper, the effects of the atmospheric boundary layer as well as the inflow turbulence on the performance of a large-scale wind turbine are investigated. The reference wind turbine is the NREL 5 megawatts with a rotor diameter of 126 meters. Wind shear modeling is carried out using the mixing length theory. Due to the importance of turbulence analysis, the Sandia method is applied. According to the reference level, the roughness coefficients of 0. 01, 0. 2 and 0. 5 and disturbances in the roughness of 0. 5 with the intensity of 1, 5 and 15 percent are studied. The aerodynamic forces of the rotor are calculated based on the modified blade element momentum theory. The results show that in the case of maximum roughness the averaged output power is reduced to 160 kW. Moreover, at 15% turbulence intensity, 50 kN and 25 kN are added to the maximum/minimum thrust force value, respectively.

Acoustic Doppler velocimetry (ADV) is one of the most suitable devices for measuring flow characteristics. Determination of measurement frequency and duration, in a way that the results are calculated with the lowest error, is very important. The goal of this study was to determine the optimum measurement frequency and duration to save money and time. 3D instantaneous subcritical flocharacteristicsts are measured at 200, 100, 25, and 5Hz frequencies for a duration of 3 minutes, in a laboratory flume with an aspect ratio of less than 5. Then, 3D averaged velocities, shear velocity, turbulence intensity, and Reynolds shear stress are calculated. Results show that the reduction of error is independent of the number of measured data and its dependence is on the data collection duration and frequency. For measurements of 3D averaged velocity components, the appropriate measurement frequency and duration are 1Hz and 50 seconds, respectively. To determine the shear velocity, using logarithmic law, reducing the frequency and duration, results in a maximum error of 13%. For calculation of turbulence flow characteristics, like turbulence intensity and Reynolds shear stress, the measurement frequency, and duration of up to 25Hz and 50-70sec, respectively, results in an error of less than 10%.

In this paper, linear accelerated turbulent pipe flow has been simulated at various Reynolds numbers using five common turbulence models. The models considered are the Baldwin-Lomax algebraic model, the Spalart-Allmaras one-equation model, theκ-e model with wall correction of Lam and Bremhorst, theκ-ω model and the κ-ε-ν2 model. The goal is to evaluate the performance and precision of these models for prediction of the wall shear stress, Reynolds stress, turbulence viscosity, delay time in response and mean velocity. Factors such as changes in pipe diameter, fluid type, initial Reynolds number of acceleration and rate of acceleration and its effect on the above parameters has examined carefully. In order to verify the results, the experimental and numerical results (turbulence modeling and Large Eddy Simulation) of other researchers have been compared with the present results. The results show the desired accuracy of the one-dimensional modeling of accelerated turbulent pipe flow in comparison with Large Eddy Simulation results (three-dimensional). The response of delay time, simulated by the models (except BL model) shows relatively good agreement with experimental data. Comparing the distribution of mean velocity, turbulent kinetic energy and turbulent viscosity shows  k-e-ν2 model leads to a better accuracy compared with the other models.

The present investigation is carried out to reveal Richardson number (Ri) effects on an homogeneous and stratified turbulence under horizontal shear. The problem is simulated via Lagrangian Stochastic model (LSM). Hence, the method of Runge Kutta with fourth order is adopted for the numerical integration of three differential systems under non linear initial conditions of Jacobitz (2002) and Jacobitz et al. (1998). This study is performed for Ri ranging from 0. 2 to 3. 0. It has been found that computational results by the adopted model (LSM) gave same findings than that of preceding works. It has been shown a global tendency of different parameters governing the problem to equilibrium asymptotic states for various values of Ri. The comparative study between the computations of the present LSM and direct numerical simulation of Jacobitz demonstrates a good agreement for both methods for the ratios of; potential energy Kθ /E and kinetic energy K/E toward the total energy E and the principal component of anisotropy b12 It has been found that Ri is the most important parameter affecting the thermal and dynamic fields of the flow. Hence, increase Ri conduct to increase the uniform stable stratification and decrease for the uniform mean shear S. It can be concluded that Ri is a main non-dimensional parameter which enable us to understand physical phenomenons produced inside stratified shear flows.