Introduction: One of the main factors in the collapse of the bridge piers in rivers is local scouring. By placing the piers in the direction of the streams, a complex three-dimensional flow is formed around the pier that has been the popular subject of research by many researchers. Methods of reducing the depth of local scouring are divided into two systems: 1. increasing the strength of bed materials around the piers by using more resistant materials, such as riprap, collar and gabion in the riverbed. 2. Reducing the strength of the main factors such as downward flow and horseshoe vortex by the deflector, blade and submerged Vane or changing the geometric shape. In the present study, the effect of the deflector shapes such as triangles and curved surface on the maximum scour depth around the pier under clear water conditions were considered. General factors of bridge pier scour include down-flows, horseshoe vortex, and wake vortex. In general, the flow impact on the pier and its separation is the main factors that form scour holes around piers. Methodology: The experiments were done in the laboratory of Khuzestan water and power authority laboratory (KWPA), equipped with a flume with a length of 10 meters and a height of 500 mm and a width of 310 mm. The flume is equipped with an electromagnetic flowmeter with an accuracy of ± 0. 1 liters per second and a weir downstream of the flume to adjust the water level. In this study, natural river sand with uniform grain size (δ g = 1. 36), relative density Gs = 2. 64 and the average particle diameter of 0. 95 mm. In all experiments, water depth was considered 100 mm. In this research, three different models of PVC deflector surface (the deflector surface shapes such as triangles, curved and simple surface) with angle's face (θ = 15, 30 and 45-degrees) were adopted. It should be noted that the angle of flow with the deflector head is calculated as α = 90-θ , which used to describe and analyze. The unprotected pier scouring studied to represent a basis for controlling and comparing with the other scour and bed change conditions. A 12-hour control experiment was also conducted on the control pier to determine the experiment time (equilibrium time), and scour depth changes were recorded in the time unit during experiments. Results and Discussion: The horseshoe vortex around the scour hole accelerates digging and transfers the sediments separated from the bed downstream with the main flow. The flow's separation from around the pier also creates perpendicular vortexes on the sedimentary bed known as wake vortexes. These vortexes are active behind the pier, separate the bed particles like a tornado, expose them to the flow, and help move sedimentary particles from the front and sides of piers downstream. The scour hole digging by the horseshoe vortex continues until the water volume inside the scour hole increases and exhausts the vortex energy. In this state, the scour depth changes negligibly over time and reaches equilibrium. The results showed that by reducing the head slope from 40 to 15 degrees, scouring depth decreases. For all deflectors with 15 degrees in the parameter (U/Uc=0. 70), the percentage of the scouring depth reduction is close to 83 to 89 percent. In the parameter U / Uc=0. 96 near inception motion that is the most critical state and the value most comparable to the particle incipient motion, the deflector with triangle surface shows a decrease of 85%, curved surface 77%, and simple 75%. By reducing the angle of the deflector, part of the flow lines didn't deviate towards the bed, which reduced the potential of the high-pressure zone created at the pier. This reduction in compressive potential reduced the flow velocity of the back vortices and, ultimately, reduces their ability to transport sediment downstream. Based on the results, the deflector with a triangle surface shape in all flow conditions had a better and lower scour hole depth than the carved and simple shape. Conclusion: This study used a deflector structure to reduce and control the scour depth around bridge piers. The flow effect was analyzed by implementing these protections and their impact in various relative velocities (𝑈 /𝑈 𝑐 = 0. 97, 0. 83, 0. 70). The scouring pattern and sediment point bar created around the pier with the deflectors protection compared with the control pier (without protection) had less scouring depth due to minor deviation of flow streamlines and reduced disturbances around the pier. Finally, the deflector with a triangle surface shape had a better response to reduce the scouring hole. The results stated that the deflector at the 15-degree angle significantly affects the flow deflection near the bed, corrects the flow pattern around the pier, and reduces scouring depth.

Introduction: Formation of air-entraining vortices in an intake leads to unsteady flow and cause problems such as vibration in hydro mechanical equipment, abnormal noises, severe fluctuations in local pressures and exacerbated cavitation conditions (Chen & Chen, 2015). As stated by (Sarkardeh, 2017) the stronger vortex the greater will be its negative effects on intake performance. There have been many studies on the critical submerged depth and vortex formation in intakes. (Kocabas & Yildirim, 2002) investigated the effect of rotational flow on the critical submerged depth in intakes and found that the vortex formation with the air-core vortex and the critical submerged depth was significantly dependent on the approach flow conditions and the inlet geometry. Therefore, a separate case study should be undertaken to address any structure with a particular geometry. In this paper, the effect of flow rate deviation due to the use of a deflector on a vertical intake was investigated. In this paper, also the variation of submerged depth, Froude number, vortex type, and critical submerged depth was discussed...

Accumulation of debris along with water flow in waterways causes irreparable problems every year. Structural methods are one of the most effective ways to reduce the risks of debris flow. In this study, the efficiency of the debris structure was investigated using flow pattern deflectors to increase the deposition retention efficiency and its effect on backwater and rapid collection of wood debris after the flood. To do this research, three different geometries of the rack, a debris mixture and three flow deflector sizes were used in the laboratory. According to the results, the best performance of the rack, despite the flow deflectors was related to the regular linear descaler with 97% efficiency and backwater was completely affected by the flow Froude Number. The V-shaped reverse rack had the lowest backwater rate of 2. 55%, that is not significant. In this study, the length of the debris carpet and the maximum height of the middle mound produced for the rack geometry were investigated. The results showed that the deflector installation led to a change in the geometry of the deposited accumulation which also accelerates the debris collection operation after the flood.

Installation of inflatable dams where previously small concrete dams used to be constructed is among the environmental solutions adhered to in recent years. An inflatable dam is a thick synthetic tube, which is usually installed across a river, and confronts the flow by being filled or emptied with air or water, to an arbitrary height. Inflatable dams may contain a deflector or lack it. As the foundation invert elevation affects the dam’s performance, it may be placed at different elevations relative to the streambed. A stilling basin is formed when the invert is lower than the streambed; otherwise, the invert basin, maybe flush with the streambed. Hydraulic parameters such as the flow rate, the depth of water on the upstream and the downstream of a dam, and the depth before and after hydraulic jump were measured and the flow energy loss over the dam was computed. A decreasing trend in the relative energy loss with an increase in the drop number was observed.

One of the most important sources of renewable energy is wind energy. We can harness the kinetic energy of the wind by using wind turbines. One of the fundamental problems with Savonius wind turbines is their low efficiency due to direct wind impact on the returning blade and applying negative torque to it. One new and cost-effective method to increase the efficiency of these turbines is to use a deflector upstream of the flow to prevent wind from hitting the returning blade and producing negative torque. Due to the cylindrical geometry of the deflector, it cannot guide the flow at an arbitrary angle. Additionally, a relatively large vortex region will form downstream of the deflector and near the turbine, which will have undesirable effects on turbine performance. These vortices can be controlled by installing flow splitter blades on the deflector. This study used computational fluid dynamics techniques in a two-dimensional simulation with Ansys Fluent software. Initially, a cylindrical deflector without flow splitter blades was designed and its simulation results were validated with previous experimental research. Then, as an innovation, a splitter blade was installed at a desired angle and directed flow towards the advancing blade of the turbine. The simulation results show that using a deflector with splitter blades at an angle of 5 degrees increases the turbine power coefficient by 23.4% compared to its state without a deflector at a tip speed ratio of 0.6.

Introduction: A spillway is an important hydraulic structure usually used to transport the controlled release of water of a dam or covey river water over its crest to the river bed downstream. Because of high bed slope, the velocity increases throughout the spillways and it reaches its maximum at the downstream which an energy dissipator structure should be designed to reduce the kinetic energy before it transported to the river bed. A flip-bucket and a Ski-jump structure are among the most common energy dissipator which dissipate the extra energy by throwing the incoming jet into the air and as a result, the air interferes with the water and then penetrate in the downstream pool. Energy dissipation control has always been one of the most significant and vital matter and concern of hydraulic scientists and researchers especially in high dams. One of the most common method to dissipate energy is to discharge flow away from the hydraulic structures and downstream by using Flip bucket spill way. During the past decades, many studies are conducted to develop a design criterion to increase the efficiency of the structure or increase of energy dissipation. The length of the projectile or the horizontal distance of the jet which passes to attach the downstream water, also has been important issue which investigators have tried to reduce as long as possible. The use of deflector installed at the edge of the upstream of the jump is among measures which was first studied by Joun and Hager (2006). Many other studies also showed that the deflector can increase the energy dissipation and reduce the projectile length. However, most of these studies focus on the geometry of the deflector. As the effect of the position of deflector have not been studied, this study was conducted. Methodology: To investigate the effects of deflector installation position on energy dissipation and the length of the projectile jet a new experimental study was conducted in the Hydraulic laboratory of Shahid Chamran university of Ahvaz. Three wedged-shape structures with height of 10 cm, length of 6 cm and angle of 47 degree were installed at four different positions upstream of the jump. Total of. 40 experiments were performed using 10 different flow discharges. It is worth mentioning that all experiments including the none-deflector case, were performed at 8 dimensionless parameter Yc/H. At each experiment the flow discharge, the water surface profile, the jet projectile length and the depth of tailwater was recorded. Photographs also was taken which were used to extract necessary data by using image processing software. In the end relative energy dissipation was calculated by measuring the total energy in the upstream and downstream. In addition to the energy dissipation, Jet projectile length (for each experiment) was determined by using Get data software and the photos taken during the study. Results and discussion: In general, data analysis demonstrated that the waged-shape structures resulted in a remarkable increase in the amount of energy dissipation and a major decrease in jet projectile length, due to the increase of water and air mixture compare to the case of no deflectors. Indeed, deflectors divide the incoming jet to two small different jets, therefore the combination of these two small jets leads to the increase in water and air mixture and consequently the increase of relative energy dissipation. Moreover, it has been shown that the energy dissipation increased directly with the linear distance from the bucket. Furthermore, the experimental study on the jet length indicated a remarkable decrease in the jet length by the increasing of the linear distance. In other words, the different installation position of deflector increases the height of jet trajectory. It directly increases the contact surface of jet and air and leads to increase in energy dissipation and consequently decrease of jet length. Conclusion: In general, the increase of horizontal distance of the installed deflector from the edge of the bucket resulted in the increase in energy dissipation and the decrease in jet projectile length. The maximum relative energy dissipation was observed 65. 9% which occurred where the Yc/H = 0. 027 and Lx/L = 7. 3 and the minimum observed relative energy dissipation was 57. 5%, which occurred for the Yc/H = 0. 061 and Lx/L = 4. 3. Furthermore, the maximum observed jet length was105 cm, which occurred in Yc/H = 0. 061 and its minimum was 35 cm, which occurred in Yc/H = 0. 027. Therefore, according to the results of the all experiments using deflector in proper possessions can significantly reduce the jet projectile length and also cause to increasing the energy dissipation. More studies in larger scale model required before the result of this study can be applied in prototype.

In the present study, using computational fluid dynamics, the effects of the use of deflector plates on the power characteristics of a three-bladed Darrieus turbine with straight blades are investigated. To this, 10 flat deflectors with inner and outer diameter ratios of 1. 6 and 8. 8 around the considered turbine are used. Computations have been carried out at a wind speed of 6 m/s and tip speed ratios (TSR) of 0. 5, 1. 5, and 2. 5. The applied code for the Darrieus turbine is validated against the available numerical and experimental data for the case without deflectors and reasonable agreement has been achieved. The obtained results reveal that the deflector plates have considerable impacts on the power characteristics of a three-bladed Darrieus turbine. Application of deflector plates around the wind turbine increases the injected flow into the rotor and hence, the velocity field inside the rotor improves. The obtained results demonstrate that the existence of deflectors enhances the mean power coefficient by 326. 3%, 70. 2%, and 201% at TSR=0. 5, 1. 5, and 2. 5, respectively.

Background and Objective: With the increment of population, the need for sustainable energy development has been raised. By increasing greenhouse gas emissions and decreasing the fossil energy reserves have also shifted research centers around the world to renewable energy sources. Among renewable energies, wind energy is one of the most important types of renewable energy. In this study, the efficiency of the Savonius wind turbine is significantly increased by using an airfoil-shaped deflector. This increase in efficiency is carried out by upgrading the self-starting performance capability of the Savonius wind turbine and reducing the negative torque generated by the returning blade. Material and Methodology: Different configurations of the proposed deflector system are considered numerically using the CFD solver. A three-dimensional incompressible unsteady Reynolds-Averaged Navier-Stokes simulation in conjunction with the SST k-ω,turbulence model is done and validated with the available experimental data. Findings: The predicted results indicated that the performance of the Savonius rotor is highly dependent on the position and angle of the deflector. Thus, there was an appropriate position and angle values to obtain the highest torque and power coefficients. It was concluded that using the favorable airfoil-shaped deflector significantly enhanced the static torque coefficient values in all angular ranges especially in the rotation angles between 0°,to 30°,and 150°,to 180°, . By properly covering the returning blade using the airfoil-shaped deflector, the static torque coefficient values increased up to 2 times higher than that generated by without deflector case. Discussion and Conclusion: The Savonius turbine suffers from poor efficiency. Hence, the present work dealt with proposing an improved deflector system led to generate higher power and torque coefficients which resulted in capturing a higher efficiency and better self-starting capability.

Flip buckets are commonly used to discharge flow from a hydraulic structure to the downstream as ski jump when flow velocity is large. One way to increase energy dissipation in flip bucket spillways is the deflector application. In this study deflector is a wedge-shaped structure which creates changes in part of flow trajectory. In this study, the deflector was continuously used across the channel, and energy dissipation caused by the mentioned deflector was measured. For the purpose of this study, after making the physical model, experiments were conducted by using four Froude’s numbers 5.55, 4.72, 3.93 and 3.13 by using deflectors with 3, 6, 9 cm lengths, and angles equal to 12˚, 17˚, 22˚, 27˚, 32˚, 37˚ and 42˚. Data analysis showed that deflectors with different anglescause an increase in energy dissipation. Also when the Froude’s number increases, the amount ofenergy dissipation will increase. The greatest difference of energy dissipation with state without deflector which occurs in Froude’s number of 3.93 was equal to 22.7% and was belong to deflector with 6cm length and 27 degree. In average the deflector with angles of 27 degrees has the greatest energy dissipation. This amount of energy dissipation for deflectors with 3, 6, 9 cm in lengths were equals to 68.2%, 72.5%, 51.6%respenctively and which occur in Froude’s number equal to 5.55.