ناهید پورعبدالله

One of the ways to improve the characteristics of the hydraulic jump in the stilling basin is to use natural and artificial roughness. Recently, due to the advantages of immersed plates compared to other non-continuous artificial roughness, such as the smaller number of these and the vanes' ability to design their geometry and arrangement, it has been approached more. In this article, the effect of submerged vanes with three contact angles of 45°, 75°, and 90° has been investigated on the improvement of the characteristics of a hydraulic jump and its effect on parameters such as the depth ratio, relative length, energy loss rate, and bed shear force coefficient has been evaluated. The results of this research showed that the average effect of submerged vanes on reducing the depth ratio, jump length, and roller length compared to the classical mode is 9.4%, 24.6%, and 28.4%, respectively and the average relative energy loss is 5.5% compared to the classical state and maximum relative energy loss at the angle of 90 degrees of submerged vanes is 6.5%. Considering these results and other conditions such as ease of construction and use, stabilization, and reduction of economic costs among the available choices of sunken vanes, the angle of incidence of 75° is a suitable option for the optimal design of the stilling basin.

Hydraulic jump is a type of rapid variable currents, which has surface turbulence and twisting of water from the beginning to the end, and is known as an energy-wasting phenomenon. In this research, the numerical simulation of hydraulic jump was done in the case of initial negative step of 3 and 6 cm, bed roughness of 2 cm and reverse slope of 1.5 and 3%. RNG and k-ε disturbance models were used in this research. Also, two types of uniform and non-uniform grids were used. According to the numerical modeling results, the RNG turbulence model calculated the turbulence of the flow field more accurately compared to the K-ε turbulence model. The statistical indices of NRMSE, R2 and d for the numerical simulation results of the water surface profile were obtained as 10.1, 0.993 and 0.994 respectively. Also, the values of these indices were calculated for the speed profile simulation results, respectively 16.36, 0.944 and 0.97. The error of the numerical model in calculating the values of the velocity profile was higher compared to the water level profile, which can be attributed to the severe flow turbulence and instantaneous velocity fluctuations in any vertical direction within the range of occurrence of hydraulic jump and intensification of air-water mixing. Comparison of the simulation results with the laboratory results of water surface profile, velocity profile, conjugate depth ratio, rolling length and hydraulic jump length and energy loss ratio shows the capability of the numerical model in the three-dimensional simulation of the free hydraulic jump flow field.

In addition to soil water content, soil matric potential is also important for plant growth. Soil water characteristic curve (SWCC) or soil moisture characteristic curve describes soil water content and soil matric potential relationship. Many models have been developed to describe the SWCCs and their fitting to the experimental data. However, their fitting accuracies in different soil textures, have been rarely investigated. In this study, matric potential-moisture data of 16 soil sample of forest station in Finland use to fit SWCC models. Nine well known and frequently applied SWCC models were fitted to the measured data. The most accurate models of total soil samples, each textural group and each textural class were estimated using root mean square error (RMSE), coefficient of determination (R2) and mean error (ME). Result showed that van Genuchten-Mualem, van Genuchten, Gardner and Brutsaert models had most accurate and Brooks and Corey model had least accurate to predict SWCC.

Hydraulic jump is used for dissipation of kinetic energy downstream of hydraulic structures such as spillways, chutes, and gates. In the present study, the experimental measurements and numerical simulation of the free hydraulic jump by applying Flow-3D software in six different conditions of adverse slope, roughness, and positive step were compared. It should be noted that two turbulence models including k-ε and RNG were used for numerical simulation. Based on the results, simulation accuracy using the RNG model was more than the k-ε model. The statistical indices of NRMSE, ME, NS, and R2 for comparing the water surface profile were obtained at 34.3, 0.0052, 0.995, and 983 for the application of the RNG model, respectively. Also, using the RNG model, the values of these indices for the velocity profile were obtained at 14.92, 0.127, 0.9982, and 962, respectively. In general, the error of the simulated water surface and velocity profile were obtained at 5.31 and 12.4 percent, respectively. Moreover, the maximum error of the numerical simulation results of D2/D1, Lj/D2, and Lr/D1 was ±12, ±12, and 16%, respectively. Therefore, the use of Flow-3D software with the application of the RNG turbulence model is recommended for numerical simulation of the hydraulic jump in different situations.

In this study accuracy of the ANFIS and ANFIS-PSO models to estimate hydraulic jump characteristics including sequence depth ratio, the jump length, the roller length ratio, and relative energy loss was evaluated in stilling basin versus laboratory results. The mentioned characteristics were measured in the stilling basin with a rectangular cross-section with four different adverse slopes, four diameters of bed roughness, four heights of positive step, three Froude numbers, and four discharges. The average statistical parameters of NRMSE, CRM, and R2 for estimating hydraulic jump characteristics with the ANFIS model were 0.059, -0.001, and 0.989, respectively. While, the mean values of these parameters for the ANFIS-PSO model were 0.185, 0.002, and 0.957, respectively. The results indicated that these models were capable of estimating hydraulic jump parameters with high accuracy. However, the ANFIS model was moderately more accurate than the ANFIS-PSO model to estimate the sequence depth ratio, the jump length, the roller length ratio, and relative energy loss.

The control of speed and pressure oscillations along the stream, as two critical parameters in designing hydraulic systems, is vital since they have to be set within an acceptable range in order to prevent damages to hydraulic structures. Ead and Rajaratnam (2002) studied the hydraulic jump characteristics on the corrugated bed and calculated the thickness of dimensionless boundary layer to be 0.45. Pourabdollah et al. (2015) investigated the effect of roughness and adverse slope of the bed on the velocity profile and determined the mean shear force coefficient to be 11.5 times more than that of the classical condition. Fiorotto and Rinaldo (1992) stated that in hydraulic jump the pressure is oscillating around the mean pressure value, which is almost equal to piezometric head at each point. Also Lopardo and Solari (1980) determined the pressure oscillations equal to 0.084 for hydraulic jump at downstream of valve. Accordingly, although various studies have been carried out on hydraulic jump characteristics under different conditions, the simultaneous effect of end positive step, bed roughness and adverse slope on hydraulic jump characteristics have not yet been explored. Therefore, the aim of this study was to investigate the velocity profiles, flow surface and pressure oscillations in hydraulic jump within the stilling basin at defined conditions.

Water after passing over weirs or through gates often has a lot of energy. If the water enters to the river with the same energy, it will damage downstream structures. Creation hydraulic jump is one of the approaches to reduce this energy. Therefore, it is important to study hydraulic jump. In this study, the characteristics of hydraulic jump on bed with vertical trapezoidal roughness with heights of 0.5, 1 and 2 cm and bed slope of 0, -1.5 and -3% were investigated. Based on the results, sequent depth ratio, in Froude number range of 4-9, was decreased by 18.8% more than the classic jump. The energy loss was increased by 9.6% compared to the classic jump. The maximum decrease in sequence depth was related to roughness with 2 cm height and bed slope of -3%. Moreover, the rough bed with adverse slope affected the jump length and caused to decrease it compared to the classic jump.

Control of hydraulic jump to reduce damage to the structures of downstream is one of the issues of interest to researchers. Although several researches have been conducted on the application of rough bed to control submerged jump but, any study has not been published on the simultaneous application of the adverse slope, bed roughness and the positive step. In this research, the effect of different adverse slopes, bed roughness and positive step height were simultaneously investigated on characteristics of submerged hydraulic jump in Froude numbers from 4 to 10 and submerge ratio from 0.1 to 1.5. The results showed that in each special Froude number, the length of submerged jump and its relative energy loss are more and less than these specifications for free hydraulic jump; respectively. In addition to, with increasing the submerge ratio, the average energy loss and the submerged jump length decreased 10 and 33%; respectively as compare to the classical state. Also, the thickness of the dimensionless boundary layer of submerged jump was 0.37. On the other hand, the shear force coefficient (ε) was calculated 4.44 times more than the classic condition.

Study on the reduction of flow energy intensity in order to reduce damage of the downstream hydraulic structures, always has been one of the potential interesting issues. One of the most important topics in this field is the study on hydraulic jump and its control method. Like other structures, in energy dissipaters considering economic and ease of construction is an essential issue. Therefore, in this study, the effects of the roughness and negative bed slope on water level and velocity profiles of hydraulic jumps for upstream flow in Froude numbers ranges of 4.9-7.8, with three different bed roughnesses and slopes of 0%, 3.1%, 60%, and % 2 were studied. The results indicated some similarities between the measured velocity profiles and some differences between the profiles of water jets as compared with those on smooth beds. Also, the thickness of the dimensionless boundary layer was calculated to be 0.66, which was significantly different in comparison with its value for the flat bed (0.16). Moreover, the bed shear stress on the rough negative sloping bed was at least 10 times greater than the shear stress on the smooth flat bed. Also, the energy and momentum correction coefficients were higher relative to the classic mode.

Hydraulic jump is a kind of the rapidly varied flow that during this phenomenon the flow profile changes from supercritical to subcritical and causes substantial energy dissipation. In this research, hydraulic jump characteristics, including length of jump and roller length of jump within the stilling basin with different adverse slope (0, -0.6, -1.3 and -2%) and three different roughness (1, 4 and 10 mm) were investigated. Results showed that these characteristics on stilling basins with adverse slope and the rough bed were reduced respect to the classic jump situations. The experiments were performed on rough beds in different conditions where the Froude number varied between 4.9 and 7.8. In this research, the total length and the length of roller part of the hydraulic jump were decreased about 39.6 and 32.3 percent, respectively.

Most of researches related to hydraulic jump have been done on horizontal and rough beds, and little attempt has been made on rough beds with adverse slopes. The aim of this study was to investigate the influence of rough beds with adverse slope on hydraulic jump characteristics. The variations of energy loss in stilling basins with three adverse slopes and three different roughnesses were studied. Results showed that increase of roughness caused that relative depth of jump in stilling basins with rough bed and adverse slope decreased as compared to horizontal smooth beds. The experiments were performed on rough beds in different conditions where Froude number ranging between 4.9 and 7.8. Result showed that reduction of relative depth was about 31.15%. Results also showed that in such cases the relative energy losses are more than that for classic conditions.