In this research, in order to investigate the effect of the piezoelectric patch which is used as a sensor or actuator in rotating flexible structures such as a helicopter blade, the free vibrations of the rotating Rectangular sheet with and without the piezoelectric patch have been presented. First-order shear deformation theory is considered for plate displacement and piezoelectric field. Considering the effect of Coriolis acceleration, centrifugal acceleration and centrifugal in-plane forces, the equations of motion are derived from Hamilton's principle and the electromechanical couple equation is obtained from Maxwell's equation. For piezoelectric, two electrical conditions, open circuit and closed circuit, which are used in sensors and actuators, respectively, have been considered. The equations are discretized with the help of the numerical method of generalized differential squares and the matrices of inertia mass, eccentricity, Coriolis and stiffness matrix are obtained. Natural frequency values for beam and rotating plate have been compared in Abaqus software. Also, the values obtained from the numerical solution in MATLAB have been verified with articles and ABAQUS, which have high accuracy. The effect of parameters such as hub radius, rotation speed, sheet thickness, aspect ratio, piezoelectric patch thickness and applied voltage on the natural frequency of the system has also been investigated.

One of the common ways of dissipating the excess kinetic energy downstream of dam spillways is the use of flip-bucket. Usually a scour hole is created on the river bed at the point of jet impingement which may cause damage to the structures. Riprap can be used to stabilize the river bed. It is the main purpose of this study to develop design criteria for riprap size. To reach such a goal, first general relations were developed at the point of the incipient motion and failure condition for riprap. These relations were developed based on the stability criteria of riprap particles using dimensional analysis. Then extensive experimental tests were conducted in a physical flume. Five different sizes of riprap materials were tested under different flow conditions. Analyzing many linear and none-linear equations, the best fit relations were developed and presented. Other tests also were conducted to establish the filter criteria which must be placed beneath the riprap materials to prevent escaping of the fine materials.

In this study, the flow dynamics of a high aspect ratio Rectangular liquid jet issued into parallel airflow was experimentally investigated using a proof of concept setup, a more appropriate setup will be designed for a complete study later. The liquid flow was emanated from a Rectangular injector with a thickness of 0.64 mm and an aspect ratio of 21. The injector was set in the center of the test section and the effects of airflow on the liquid flow were evaluated. A particular holding mechanism was designed and built to minimize the induced perturbations on the liquid flow. To identify the physics of the liquid flow shadowgraphy technique and high-speed imaging were implemented. In order to provide a comprehensive study of the problem, the experiments were performed for a wide range of flow conditions, and flow visualizations were presented. jet Weber number and Gas Weber number were varied from 3 to 120 and 0.2 to 12, respectively Also, five regimes of the liquid flow including column, column/gravity, arcade, bag, and multimode were recognized. A mapping with gas Weber number and momentum ratio as the determining variables was suggested to distinguish these regimes from each other. The breakup length of the liquid jet was also measured. It was found that with the increase of jet Weber number the breakup length was increased at constant gas speed. Moreover, it was revealed that the breakup length was elongated with the increase of gas Weber number.

The present study was conducted to simultaneously investigate the effect of Rectangular free jet and semicylindrical roughness on hydraulic jump characteristics. This study was performed inside a flume in the form of a Rectangular channel 10 meters long and 30 centimeters wide. Then the jet with flows of 3/2, 2, 2/5 Liters per second with the maximum displacement effect of the beginning of the jump and the angle without changing the beginning of the jump to the end of the hydraulic jump. Take this angle as The angle was named ineffective and with the increase of the jet angle, the jump moves upwards and from one angle onwards, the jump does not move upwards. This angle was named as the maximum displacement angle. Decrease or increase, jump length, The secondary depth of the relative energy drop and shear stress force of the bed is used. The secondary was smoothed to a jetless state. Deployment The jet with an angle of 127 (inertial angle) degree, maximum landing number (9. 64) flow and semi-cylindrical roughness reduces to 0. 12% compared to the state without jet and smooth bed. The highest reduction in jump length (34. 7%) occurs when the maximum flow angle from the jet and the flow rate is 3. 2 liters per second and in the conditions of the lowest landing number (6. 64) and the maximum increase in the 70 degree angle mode, the maximum jet flow And the maximum landing number in a flat bed is 8. 16%.

The aim of this study was to investigate the effect of jet and reverse slope on the characteristics of hydraulic jump. This study was performed inside a flume in the form of a Rectangular channel 10 meters long and 30 cm wide. free jet with flows of 2, 2. 5 and 3. 2 liters per second with the maximum displacement angle of the beginning of the jump and the angle without changing the beginning of the jump to the end of the hydraulic jump. The results showed that changes in the angle and flow rate of the jet reduce or increase the secondary depth, jump length, relative energy loss and shear stress force of the bed. Using a jet with a maximum angle and flow rate of 3. 2 liters per second with the lowest landing number Reverse flow and slope reduced the secondary depth ratio by about 56. 2% compared to the no-jet mode and smooth bed. Using a jet with a minimum angle and flow rate of 3. 2 liters per second and the maximum flow rate increased the secondary depth ratio relative to jetless mode was smoothed. The results of this study show that at a certain angle from the jet to the hydraulic jump, there is no displacement in the jump, which was named as the inert angle, and by increasing the angle of the jet jump upwards, the hand jumps to It moves upstream and from one angle onwards the jump does not move upwards. This angle was named as the maximum displacement angle. Changes in the angle and flow rate of the jet reduce or increase the secondary depth, jump length, relative energy drop and stress force. The use of a jet with a maximum angle (138 degrees) and a flow rate of 3. 2 liters per second, the minimum number of landings (6. 64) and reverse slope reduces the ratio of the secondary depth to about 56. 2% relative to the state without jet and bed was smoothed. Using the jet with the minimum angle (78 degrees) and the flow rate of 3. 2 liters per second and the maximum number of landings (9. 62) flow increased the ratio of secondary depth by 15. 3 percent compared to the state without jet and smooth bed.

The flow from the dam is a tremendous amount of energy in the absence of energy dissipation, the flow through the irreversible damage to structures downstream of the dam. A one way of dissipating the excess energy is falling jet in the plunge pool. Flow jets in special distance have a dense core which formed of water particles. Much of the pressure on the bed and pool wall is caused by that dense core. After passing some distance, air Intrusion from border and flow turbulence causes to shrinking core and finally it will be vanished. This study examines the failure of the jet length and the parameters affecting it are discussed. Percent from the second to the third experiment the Froude number, approximately 15 % decrease and finally tests the third quarter increased 17 percent compared to 6 percent of the Froude number increases. So we can conclude that the changes failed to increase the jet flow (Froude number) is not constant after reaching a minimum point of the process increases. Further statistical analysis was determined according to the coefficient of expansion jets in turmoil with the failure probability 0. 1 is significant.

The energy available in the terminal of dam structures causes erosion of the river bed. Different parameters such as discharge, difference between upstream and downstream, radius of jet, mean diameter of bed materials, velocity of the jet and the tail water are recognized on the score hole and its geometry. The cognizance of these parameters aids the designers to provide a suitable layout for the scoring pool...

The dynamic behavior of a very large Rectangular floating structure is considered. The structure is modelled as a plate with free edges. Two different thicknesses are considered for the model. The Mindlin plate theory is used to formulate the structure behavior. Natural frequencies, mode shapes, and stress resultants of the structure are predicted by using finite element method. For this purpose, a MATLAB code is written. The same analysis is performed by using the ANSYS software. The results of these two analysis are compared with each other and with the available results in the literature, where close agreement is observed. Therefore, the written finite element code is found to be acceptable for prediction of the dynamic behavior of very large Rectangular floating structures in early stages of design.

Introduction: Prediction of scour and characteristics of scour hole due to out flow from hydraulic structures is important in the hydraulic engineering. The dimensions of scour hole are influenced by different parameters including: flow discharge, drop height of flow, tailwater depth, sediment size, sediment load and time of scouring. Almost all the previous studies have focused on the scour hole characteristics downstream of free over fall clear water jets. Water jets are not always clear and may carry sediment, especially during flood condition, and the effect of sediment load on the scour characteristics are not well studied. Therefore, in this study, scour downstream of a free over fall clear and sediment-carrying water jets are studied experimentally. The main purposes of this study are to analyze the effects of important parameters including sediment load, sediment size and discharge of the free falling jet on the scour depth and the longitudinal scour length. The temporal variation of the sour depth and longitudinal scour length were also addressed. New dimensionless equations for scour depth and longitudinal scour length were obtained. Methodology: Experiments were conducted in a Rectangular channel of 0. 6 m width, 12 m length. The water was pumped from a sump to the channel. A Rectangular free-overfall jet of 0. 21 m width was established at the last 1 m length of the channel. Scour was simulated in a Rectangular box of 1. 5 m width and 2. 51 m length, which is located downstream of channel. Measurement of discharge was done by using a calibrated sharp crested triangular weir with 90 degree apex angle. The depths of flow and longitudinal bed profiles were measured by using a digital point gauge with ± 0. 01 mm theoretical accuracy. Temporal measurement of longitudinal bed profiles were also done by using the same digital point gauge. The Rectangular box was covered by uniform sand layer with 0. 45 mm thickness. Experiments were performed for four different discharges (4. 27, 7. 48, 11. 78 and 17. 3 L/s) and two sediment sizes (d50 = 0. 6 mm and 1. 2 mm). Experiments were conducted with clear water free falling water jet and sediment caring free falling water jet. In experiments with sediment caring free falling jet, the dry sediment with constant rate was added to the water jet by using a sediment fidder. Four values of sediment load: 0. 25, 0. 5, 1 and 2 kg/min were used. The added sediment to the jet was of the same size as the downstream bed material size (d50 = 0. 6 mm and 1. 2 mm). Time variations of the scour depth and length of scour hole were also studied. Results: Based on the result, by increasing the sediment load, the values of maximum depth of scour and length of scour hole decreased. The rate of scour reduction depends on the amount of sediment load in the water jet, water discharge and duration of scour. By increasing the duration of experiments, the increasing effects of densimetric Froude number and jet discharge in the longitudinal bed profiles reduces. The decreasing trend of sediment load on the maximum scour depth is more pronounced in experiments with lower duration. In higher discharges, the reducing effect of the sediment load on the maximum depth of scour reduces. The reducing effect of sediment load on the longitudinal scour length is reduced for higher water discharge. The reducing effect of sediment load on longitudinal scour length is enhanced in experiments with lower duration. Effects of dimensionless parameters on the scour depth and scour length were addressed. By increasing the densimetric Froude number, the relative depth of scour and relative longitudinal length of scour hole increases. The dimensionless equations for estimation of the longitudinal scour profile, scour depth and scour length are obtained. Conclusion: In this experimental study, the scour depths and the longitudinal scour lengths were compared in the clear water and sediment caring free falling water jets. It was found that by increasing the sediment load, the values of maximum depth of scour and length of scour hole decreases. The rate of scour reduction depends on the amount of sediment load in the water jet, water discharge and scouring time. New equations for estimation of the longitudinal scour profile, scour depth and scour length are also developed.

Bucket spillways are used at the end of high dam spillways due to low cost compare to other types of energy dissipater structures. Impingement of falling jet on the river bed can create scour hole which can cause damage to the spillways, dams body or nearby structures. Accumulation of sediment downstream of scour hole can increase the tailwater and reduce the hydropower generation. Therefore it is important to predict the scour depth when using flip bucket as energy dissipater. The purpose of this study is to conduct experimental tests to understand the mechanism of this phenomenon and to develop relationships for predicting the scour holes dimensions. To reach these goals, at first by dimensional analysis, general relation was developed. The maximum depth of scour holes was found as a function of variable containing discharge, jet thickness, height of falling, particle size and densimetric froude number (SN), which is the ratio of the total active force to the total resistance force acting on a single particle. Then an extensive experimental program was conducted under different size materials and flow conditions. Using the experimental data, different models were examined and the best models were selected. The best models for predicting the maximum scour hole were achieved with variables of discharge, height of falling and particle size. No accurate models were achieved to predict the height of point bar upstream and downstream of scour hole. Finally, these models were tested by applying experimental data from other investigators and it was found that the models presented in this paper can predict the scour depth accurately.