Using openfoam, numerical simulations of two-dimensional flow past a stationary and harmonically pitching wind turbine airfoil at a moderate value of Reynolds number (400000) have been carried out in the current study. Wind turbine blades are subject to different oscillating motions due to unsteady flow around them. Therefore, sinusoidal pitching motion as one of the basic motions in an unsteady oscillation is needed to be thoroughly investigated. This helps to reduce the loads on blades occurring due to dynamic stall phenomenon. The aim of this numerical study is to enhance the accuracy in prediction and analysis of unsteady phenomena around an oscillating NACA 6-series airfoil at near-and post-static stall regions. The experimental data possessed by the presenting authors are considered for validation. In most cases as the results demonstrate, the numerical simulation along with turbulence modelling using k-ω-SST with low-Re correction can accurately capture the physical phenomena related to unsteady pitching motion and hence, highly precise aerodynamic coefficients and pressure coefficients around the airfoil will be obtained at different stall-wise regions.

In order to increase the performance of a gas centrifuge used in the uranium enrichment industry, the gas flow field inside it is studied and simulated. In the present work, the full Navier-Stokes equations using the CFD method are used to simulate the gas flow inside the rotor. For the CFD method, a density-based implicit coupling solver was developed in openfoam software, which was used to simulate the gas flow inside the rotor. The separation power was improved in a sample rotor by adjusting feed flow parameters, wall pressure, wall temperature gradient, and scoop drag force. The results show that the process variable had an optimal value in which the separation power is maximum. In order to achieve the maximum separation power of 12. 87 kg UF6 SWU/year, the optimum rotor conditions were determined at a feed rate of 90 g/h, wall pressure of 44 torr, the temperature gradient of 25 K, and drag force of 1557 dyne. This study can be considered an important step in improving the performance of centrifuge separation.

In this article, rigid wedge water entry problem under different conditions is evaluated using numerical scheme Rigid wedge water entry continues to be one of the fundamental issues raised in the hydrodynamics studies and is known as a reference for the study of slamming phenomena. The exact calculation of the pressure caused by the slamming phenomenon can be used to analyze the appropriate structural analysis of the ships. In the current study, important variables such as speed and fluid pressure are investigated using computational fluid dynamics method based on the open source Open FOAM code by numerical solution of the governing equations of tow phase fluid. In order to verify the simulation results obtained from this research, Tthe values of the maximum pressure and the location and exact time of its occurrence and also pressure coefficient distribution at the impact region have been compared by experimental results of other studies. These investigations have been utilized at different impact velocities and angles. By comparing the numerical results and experimental values, an error was found in the range of 2% to 9%. In addition, variables affecting the pressure applied to the wedge such as water entry velocity and different deadrise angles have been studied.

Culvert is one of the main structures in drainage systems at crossing with railways and roads. Flood flows, along with the transport of sediments and floating debris, can cause blockages and backwater, thereby reducing flood flow capacity. The main purpose of this study was to physically model and numerically simulate the effects of different percentages of blockages on culvert hydraulic characteristics. Blockage effects investigated in 21 laboratory experiments. Complementary tests were carried out with the use of openfoam numerical tool box. Three blockage scenarios have been numerically simulated with 20, 40 and 60 percent coverage of inlet area. The numerical model was calibrated using the experimental data. The simulation results of openfoam in different culvert inlet blockages indicated that the LES turbulent model is more adaptive than RAS models. The main flow characteristics were compared with the corresponding simulation results from the trademark FLOW-3D model, and showed good agreement for verification purpose. Results for different flows (i.e. 40, 60 and 100 percent of the design discharge) showed that the increasing rate of upstream water level is not identical, and is higher for the lower discharges. Blockage also intensifies turbulence and shear stress levels in the outlet section. For design discharge, the 40 percent blockage resulted in the increase of shear stresses up to 10 times, which cause severe scour in downstream channel.

One of the coastal protection techniques is the use of breakwaters. This study aims to investigate the effect of pile breakwaters on coastal waves. These breakwaters are similar to a porous structure. They are preferred over other impenetrable coastal structures due to their increased roughness and resistance to the current, their relatively low cost, economic savings, greater environmental compatibility, and preservation of natural landscapes. Considering rigid cylindrical obstacles on the coast with constant slopes, the effect of their roughness on flow patterns and waves by numerical modeling in openfoam software was investigated. The method used in flow modeling is the RANS method and k-ω, SST model. Modeling was performed in two modes with and without barriers for three different heights of wave. The results were compared with laboratory data. The absorbed force for wave height of 6, 9, and 12 cm in the numerical model was 17.14, 4.23, and 7.86 percent, respectively, with the laboratory model, Also, the mean square root of normal error was 0.07, and the correlation coefficient was 0.99, which indicates the conformity of two numerical and laboratory models and the appropriate performance of Open FOAM software in modeling. Keywords: Coast protection, Pile breakwater, Wave energy,

Surface-piercing propellers (SPP) are known as one of the most efficient propellers in marine sciences and maritime industries. In this study, different types of simulations were performed on an SPP in various rotational speeds in open water conditions, and a numerical study was also carried out on a particular type of such propellers. In fact the main purpose of this paper is comparing the simulation results with the experimental results from past in order to derive a trustable soultion for future works. For this purpose, the surface-piercing propeller was simulated by openfoam software (an open source software with high range of capabilities)  in order to analyze the results. The performance curve was then plotted and compared with the ones from open water tests. In this case the turbulance model of K-Epsilon RNG was used which is capable of increasing Y+ to 300 which is monitored at the end of the simulation with the maximum amount of 315 and the average of 80.  Results showed that the curves followed the same pattern and trends in the numerical study, and the report pointed to similar findings. In conclusion, it was proved that the sliding mesh method was a proper way for simulating propellers, particularly SPPs. The curves for thrust and torque coefficients of the SPP were also compared with the literature and the efficiency curve was plotted.

Taylor bubbles are commonly utilized in a wide range of industrial applications involving non-Newtonian fluids, and a thorough understanding of the relevant knowledge is helpful to the design optimization of related industrial processes. This study investigated the behavior of Taylor bubbles in shear-thinning fluid using openfoam. The numerical method is verified by comparing the results with experimental data, additionally, the effects of flow index n, surface tension σ, and zero shear rate viscosity μ0 on the motion behavior of Taylor bubbles were investigated. The results show that as the flow index n and zero shear viscosity μ0 increase, the terminal velocity of the Taylor bubbles decreases. The impact of various operating parameters on the bubble nose's form is insignificant. Regarding the liquid film surrounding the bubble, when n is small, the bubble rear is broken seriously, resulting in a shorter bubble and thinner liquid film. As the flow index n increases, the bubble elongates, and the liquid film becomes thicker, the length of the wake behind the Taylor bubble decreases. The surface tension mainly affects the bubble rear but has little impact on the bubble nose and rising velocity. For high μ0, the bubble rear does not break, and the shear thinning area is small.

AbstractIntroduction: The use of numerical methods is widely used in diagnosing the performance of hydraulic systems and optimizing them. Numerical modeling is less expensive than experimental work. Numerical methods can be used to check the accuracy of the results and compare them. In this thesis, the fluid volume method is used to simulate the free surface flow of water inside the lower discharger of Kani Sib Dam. Since the flow inside the dischargers is turbulent, k-ε, k-ε RNG, k-ω SST, k-ω and also LES turbulence models have been used and compared. Also, the discharge coefficient inside the lower discharger and the aeration flow have been investigated and compared.Methods: To simulate the turbulent flow inside the lower discharger, continuity equations, momentum, energy and equation of state along with equations related to the aforementioned turbulence models have been solved using openfoam software.  The set of equations of conservation of mass, conservation of momentum and energy for turbulent flow, which are so-called Reynolds averaging equations, are the governing equations of the flow and are used to model the flow by solving them numerically.Findings: The simulation and optimization of the hydraulic parameters of the turbulent flow in the lower dischargers of the Sib Mineral Dam has been completed using openfoam. The results have been made on the parameters of the lower discharger of Sib mineral dam. And the optimization is done using genetic algorithm. In this research, it was found that with the increase of the hydraulic diameter, the discharge coefficient increases. Also, with the increase of the hydraulic diameter, the core of the water fluid jet inside the discharger undergoes a strong fluctuation, which can increase the shear stress. An excessive increase in shear stress can cause corrosion of the discharge walls. On the other hand, with a further decrease in shear stress, deposition inside the lower discharger increases. At the same time, with the increase in the length of the lower discharger, the discharge coefficient decreases. The optimal selection of the length of the lower drain depends on the height behind the dam. As the opening rate increases, the discharge coefficient also increases and the k- ε turbulence model gives more acceptable results to estimate the results. Finally, for each aeration flow rate, a set of optimal values for the discharge coefficient and the opening rate has been obtained.