mehdi lak

Stepped spillways have received special attention today for their simultaneous operation in energy transfer and dissipation. In designing these spillways, the best way is to achieve a design with the highest amount of energy dissipation in the downstream and the lowest design cost. In this study, a multi-objective optimization model based on weed algorithms (IWO) and water cycle (WCA) is used to design stepped spillways with the aim of minimizing implementation costs and maximizing energy dissipation. The efficiency of the developed model was tested on the spillway of the down Siah Bisheh Dam. The results showed that the IWO algorithm has better accuracy and convergence speed than the WCA algorithm in solving the problem of multi-objective stepped spillway optimization. It was also found that using a multi-objective optimization approach can provide a set of answers to designers who can choose a suitable design for implementation in any situation depending on the amount of cost and energy consumption. Comparison between the responses with the lowest concreting volume provided by the IWO compared to the Spillway plan implemented, reduced the concreting volume by 20% and increased the energy dissipation by 12%. For the WCA, it also reduced the volume of concreting by 10 percent and increased energy dissipation by 4.89 percent.

Step spillways are an example of these massive hydraulic structures that, in addition to passing the excess water of the dams, also cause the consumption of flow energy downstream of the dams. Considering the complex hydraulics of the flow on these spillways and the presence of nonlinear limitations, their optimal design is a very difficult problem. In this study, a new framework based on Metaheuristic algorithms, including Harris's hawk Optimization (HHO), gray wolf Optimizer (GWO), invasive weeds Optimization (IWO) and water cycle Algorithm (WCA), considering the minimization of the amount of concrete used in spillway and the maximization of energy dissipation in Spillway toe were developed as objective functions to design these spillways. Algorithms' performance was first checked and validated on basic functions. Then, to achieve the objectives of the study, the spillway of the Siah Bisheh dam was selected as the study dam and the efficiency of the developed models based on the four mentioned algorithms was evaluated on it. The results showed that, in addition to improving the current spillway design in terms of construction costs and dissipation energy, the HHO-based model has good accuracy and convergence compared to other Metaheuristic algorithms. As the comparison of the design obtained from HHO with the current spillway design showed, in addition to a 35% reduction in the volume of concrete consumed, the amount of energy dissipation increased by 15%, which indicates the success of the design model developed in a multi-objective manner using HHO.

In this study, the ogee spillway flow pattern under the influence of the spillway curve shape and upstream slope changes was evaluated using Flow-3D numerical simulator software. Thus, two ogee spillways with elliptical crest and USBR pattern were simulated in two vertical and oblique upstream modes with a slope of 3H:3V and three different heads, and the results of changes in effective parameters such as flow, velocity and pressure in the length of each spillway was examined. Validation of the results of the numerical model with the results of the Maynord experimental model showed that the Flow-3D numerical model has a high ability to simulate the flow field on the ogee spillway. Comparison of flow rate from numerical model with experimental data showed that the average computational error was less than 3% of the numerical model. Examination of the pressure field showed that at the height of the head equal to the design head, the pressures are close to atmospheric pressure and no negative pressure is created on the spillway crest, but at the head higher than the design head, negative pressure will be created on the spillway. The amount of negative pressure created at the beginning of the USBR spillway crest is higher than the negative pressure value of the elliptical spillway crest due to the lack of continuity in the crest and further separation of the flow lines from it.  The results also showed that the ogee spillway with oval crest has a relatively better performance in the flow over the spillway and in these spillways it is possible to pass more discharge with higher safety and sloping the upstream side of the spillway causes a change in the discharge coefficient and finally the flow rate of the spillways.

Tunnel design and construction in developed and developing countries have been widely considered by government officials to maximize the use of underground space. Meanwhile, the presence of groundwater, crushed rock masses and faults are among the problems of the tunnel passage that seriously affect the underground space. If for any reason the tunnel route cannot be changed, the tunnel can be designed and implemented in the vicinity of the fault with safety solutions. The accuracy of the correct design of these tunnels is due to the passage of the fault through or near the tunnel, which are of special economic and safety importance. Therefore, in this article, the effect of the fault around the Noghre Kamar tunnel located in Markazi province with different directions and different distances on a tunnel was investigated, and these results and suggestions can have significant recommendations for designers. This analysis has been investigated using finite element numerical modeling (Plaxis) and finite difference (FLAC).The results show that with increasing the distance of the fault from the tunnel axis, the amount of displacement and damages are significantly reduced and with increasing the thickness of the fault, the opposite is true. The average maximum displacement obtained from Plexis and Falak software is 17 and 17.5 cm, respectively, in the case of a 90-degree fault with a width of 3 meters, and in the case where the fault intersects the tunnel at a 45-degree angle, it is 13 and 13.5 cm, respectively. Also, the total stress changes in the position where the fault intersects the tunnel at an angle of 45 degrees is the minimum and in this position the maximum value of the safety factor is obtained.

Ultrasonic needle penning is a modern technique that enhances the surface properties of metallic components by imposing static and dynamic loadings. The efficiency of this technique dramatically is dependent on the process parameters. In this study an experimental and numerical investigation on ultrasonic needle penning was carried out. The numerically predicted residual stress profile was verified using X-ray diffraction measurement of residual stress. A 3D finite element model of ultrasonic needle penning was simulated by ABAQUS software. Moreover, a parametric study was performed to investigate the effects of needle diameter, amplitude, device moving speed and static force on residual stress distribution. In order to design of experiments and determine the optimized process parameters of ultrasonic needle penning, Taguchi’s method was implemented. Based on the results, needle diameter had the lowest impact on maximum compressive residual stress and residual stress increases by increasing amplitude and reducing device moving speed. The maximum residual stress was achieved for the needle diameter of 4mm, the amplitude of 16µm, the device moving speed of 1.5cm/s and the static force of 10N. For the optimum case, compressive residual stress was improved 24%.