In this study, flow behind rectangular vane type vortex generators mounted on a flat plate, is numerically simulated using the immersed boundary (IB) method. In the present work, the direct forcing IB method is employed because of its simplicity and high efficiency. Vortex generators of two different heights are numerically investigated. The height of vanes in the first case is close to the definition of submerged/lowprofile vortex generators while the other case is closer to the definition of a conventional vortex generator. The resultant highly three-dimensional flow and its transition to turbulence have been studied. Counterrotating vortices generated by these passive rectangular vortex generators are characterized. Streamwise evolution of non-dimensionalised maximum values of vorticity, vortex strength, streamwise velocity and wall-normal velocity are studied. The simulations show that the IB method in conjunction with DNS effectively simulates the time-dependent flow behind an array of passive vortex generators placed in an initially laminar boundary layer.

Sharp-Crested weirs as measuring devices are widely used in hydraulic laboratories. They are also useful as water surface or flow controlling structures at many irrigation networks. In this paper, an attempt was made to simulate flow over rectangular and triangular sharp-crested weirs with flow under slide gates. Based on the continuity equation, an empirical equation for the coefficient of contraction, and also discharge coefficient of the rectangular slide gates, flow discharge over rectangular and triangular sharp-crested weirs are proposed. A comparison was made between the proposed theory and few experiments conducted at Isfahan University of Technology. The proposed empirical equation was also compared with those of other researchers. The results showed that the proposed method could predict flow discharge over the weirs with high accuracy.

This work deals with a numerical study on forward-facing steps situated in a supersonic flow. The primary aim of this paper is to examine the sensitivity of the velocity, density, pressure and temperature due to the step-height variations of such forward-facing steps. Effects on the flowfield structure due to variations on the step height have been investigated by employing the Direct Simulation Monte Carlo (DSMC) method. The studied parameter contours for various values of step heights and profiles in three different sections of the channel are obtained. The results indicate that the fluid flow and temperature characteristics considerably depend on the step heights. The results were also compared with the previously published works which approved outstanding validation.

A new turbulent model based on Delayed Detached Eddy Simulation (DDES) with non-linear eddy viscosity model (NLEVM) was developed to predict the complex turbulent flow. The numerical simulation of the triangular cylinder and the centrifugal pump was carried out to investigate the ability and applicability of the DDES model based on NLEVM (DDES_NL). Compared to the turbulent model based on the eddy viscosity model, the computational results of the triangular cylinder showed the advantage of the non-linear eddy viscosity modification in the DDES_NL model which can improve the accuracy of the prediction in the flow phenomenon with a relatively simple turbulence structure. Regrettably, some small-scale turbulent structures among those still cannot be captured accurately. The numerical simulation of the centrifugal pump predicted by the DDES_NL model shows more abundant flow structures and gets close to the realistic statistical characteristics. It also proves the good applicability of the DDES_NL model in complex flow. This study aims to contribute to the growing area of turbulence modeling by exploring it.

The present study is devoted to an approximate modeling for numerical simulation of flows past oscillating airfoils. In this study, it is shown that the harmonic oscillating objects can be studied by simple numerical codes that are unable to solve moving grids. Instead of using moving grids for the simulation of the flowfield around an oscillating airfoil, this unsteady flow is solved on a fixed grid having oscillated its free stream velocity vector on the boundaries. It is shown that, with a time shift, resulting airfoil forces have a good agreement with moving grid results. This time shift, which is not noted by others, is the time that takes for the flow to move from upstream boundary and pass the airfoil completely. Resulting Cl - α ellipse diameter using this approximate modeling, is only a little bigger than the experimental results. This modeling is applicable in simple codes that are not able to model moving grids.

Introduction: Bridges are certainly one of the most important structures but costly service elements in a transport system. The bridges are very required to access the damaged areas in emergency situations such as floods and earthquakes. Scour around the foundations of bridge piers exposed to the flowing water than can destroy the bridge itself is a subject of major concern. Flow pattern is known as responsible for all changes in stream bed. Any obstacle in the channel can form new flow patterns causing additional shear stress exerted on the bed than the equilibrium condition of the absence of the obstacle. Appropriate shaping of flow pattern and proper selecting of pier geometry and the location of bridge piers can be one of the proper methods in reduction of scour amount which is the main subject of the present study.Materials and Methods: Inclined bridge group pier is a type of bridges with modern geometry based on development in building technology of structures. Many of these bridges have been built all around the world and the 8th bridge built crossing the Karun River in Ahvaz is a sample of the Iranian ones considered in this research. Hydrodynamic behavior of flow is investigated around the inclined bridge group pier settled on foundation using the FLOW-3D numerical model. Inclined bridge group pier investigated in this study, includes two rectangular piers which are 2.5 cm long and 3.5 cm wide and set in an angle of 28 degree on rectangular foundation which is 16 cm long and 10 cm wide and installed in three different foundation levels namely at, above and below the bed levels. The physical model of prototype pier considered in this study was constructed to the scale of 1: 190 of the Ahvaz 8th bridge. In order to verify the accuracy of the numerical model, velocity data obtained from image processing technique were used.