In the present study, the hydraulic characteristics of vertical drops with screens and the gradual wall expanding downstream using FLOW-3D software are investigated. For this purpose, two porosity ratios of the screens of 40 and 50%, 5 Gradually expanding with 3 vertical drop heights in the specified discharge range were used. It was found that the numerical results are closer to the experimental results with the RNG turbulence model than k-ε, . By increasing the drop height, the Δ, E/E0 due to the jet floor impact intensity increased and yp/P value decreased. The maximum Δ, E/E0 for 25 cm height was 51. 60% and the lowest for 15 cm was 44. 25%. For a constant drop height with increasing discharge, the Δ, E/E0 decreased and yp/P increased. The Gradually wall expanding causes turbulence on the edges and a non-uniform distribution of yd/P and by increasing yp/P and yd/P, it caused a 25% increase in Δ, E/E0. The presence of screens increased yp/P, yd/P, and Δ, E/E0 by 44%. The simultaneous use of Gradually walls expanding and screens caused a 46% increase in Δ, E/E0 and a decrease in yp/P and yd/P values. It was shown that the contribution of screens is greater than the Gradually wall expanding, with their simultaneous application increasing Δ, E/E0 up to 33. 5%.

In this research an Artificial Neural Network (ANN), with multilayer perception structure, was adapted to model conjugate depth and Gradually expanding jump length, which are especial but complex cases of hydraulic jumps. More than 3000 interpolated and experimental data on conjugate depths and jump lengths for both normal and Gradually expanding jumps were used. The data was due to rectangular and trapezoidal sections, for a wide range of divergent angles and side wall slope. In developing the ANN models, seventeen configurations, each having a different number of hidden layers and/or neurons, were investigated. The optimal models were capable of predicting conjugate depth and jump length for a wide range of conditions. In each case, the configuration attained highest R2 value was selected as the optimal model. For rectangular sections, the simplest ANN model had a 2-2-1 configuration, with one neuron in each of the two hidden layers, and R2=0.97 (for normal x section), and had a 4-1-1 configuration, with nine neurons in the hidden layer and R2=0.91 (for Gradually expanding x-section), respectively. The best ANN model for predicting respective jump lengths had 3-2-1 and 4-1-1 configurations with one and three neurons) in hidden layer(s), and R2= 0.99 and 0.94, respectively. For trapezoidal sections, the simplest ANN model had a 4-2-1 configuration, with nine neurons in each of the hidden layers and R2=0.99 (for normal x-section), and had a 5-2-1 configuration, with six neurons in each of the two hidden layers and R2=0.94 (for Gradually expanding x-section), respectively. The best ANN model for respective jump lengths had 42-1 and 5-2-1 configurations, with nine and six neurons in each of the two hidden layers, and R2=0.90 and 0.85, respectively. The high values obtained for R2 in all of the eight cases, suggest a close agreement between the Ann's output variable and the experimental data. The developed ANN models in this paper are, therefore, suitable for predicting Gradually expanding hydraulic jump characteristics, which require a large amount of repetitive computations, for both rectangular and trapezoidal sections often encountered in the design of stilling basins.

In the present study, the effect of vertical drop, Gradually expanding and vertical screens are investigated to increase the efficiency of the energy dissipation of the flow. The experiments were carried out in a horizontal laboratory flume with a rectangular cross section, two vertical drop heights, and the wall expanding ratios of 0. 5 to 1, the porosity ratio of the screens of 40% and 50%, and The range of Froude number of 0. 86-0. 92. The results showed that the use of screens and expansion of the walls would increase energy dissipation and decrease the pool depth and the downstream depth. The application of expanding wall, screen and the effect of simultaneous use of screens and expanding walls increases the efficiency of energy dissipation by 25, 44 and 48 percent, respectively. The porosity ratio of the screen is not much efficient in energy dissipation, but it reduces the pool depth and increases the downstream depth. In the same hydraulic conditions, energy dissipation is increased and the depth of the pool decreases by increasing the height of the drops due to the increased jet severity over the drop striking the downstream bed. By increasing the discharge, the hydraulic jump formed in the upstream of the screens with a porosity ratio of 40% is submerged and moves upwards. However, in screens 50% of the jump is free and moves downward.

expanding stilling basins not only are effective energy dissipators, but also appropriate translations between hydraulic structures. Hence, the present study aims at numerical simulation of the effect of end-sill location on the energy dissipation. Doing so, Fluent software was employed and hydraulic jump under two divergence angels and four end-sill locations in the range of 4 to 8 Froude number was examined. According to the results, for larger expansion angles, the sequent depth and jump length are lower and energy dissipation is much more. Moreover, as the end-sill closes to the basin’ s entrance, the lower sequent depth, shorter jump, and less energy dissipation are observed. For very close locations more instability in the flow surface are seen. Results showed that for a given expansion angel, improving the location of the end-sill can decease 20% the conjugate depth, enhance 90% the amount of energy dissipation, and reduce 26% the jump length.

Great difference of flow depth and Manning's roughness coefficients in main channels and floodplains, generate a strong gradient of lateral velocity and hence, a lateral shear stress in the interface of the main channel and floodplain. This phenomenon increases the head loss in river system. Mathematical models which are currently used for water surface profile computations in rivers, e.g. HEC-RAS and MIKE11, neglect this mechanism. For taking into account this mechanism, the energy slope and energy correction factor should be modified in Gradually varied flow computations. In this paper, using exchange discharge method, the current procedure of Gradually varied flow computations were modified for compound channels. Comparison of this method and HEC-RAS results in an experimental flume with heterogeneous compound section in case of drawdown profile, M2, showed that the accuracy of these methods are 95 and 84.5%, respectively.

In a control structures, it is often preferred to minimize the gate width while utilizing the canal width in full for a stilling basin. Therefore, to reach this, a Gradually diverging stilling basin may be used. In this study, the effect of broad-crested sill on the expanding hydraulic jump in a rectangular channel was investigated. A total number of 79 tests were carried out for the range of initial Froude number from 3.1 to 10.3. Sills with various heights and of different locations, relative to the jump toe, were installed in the basins with divergence angles of 3 and 5 degrees. In all the tests, the main characteristics of hydraulic jump including sequent depth ratio, relative length of jump and longitudinal surface profile were recorded. The results indicate that installing broad-crested sills exert an insignificant effect on the sequent depth ratio but may considerably decrease the length of jump. In addition, observations indicate that the increase in divergence angle of stilling basin will increase the effect of sill in decreasing the jump length.

Toreducetheconstructioncostsofstilling basinsofhydraulic~umptype is sometimes,novelgeometriesaresometimes usedto adoptthe basinto the upstreamand downstreamsectionswithout any transition structures.Otherwise,any changesin thegeometryofthe basinwould causechangesin theconditionsandcharacteristicsofthe hydraulicjump. In this study,the effectsof variationin boththe sideslopesandthe divergingangleof a Graduallyexpandingstillingbasin with trapezoidal section on the jump condition were experimentally investigated. The experimental tests were conductedin a speciallydesignedmodelfora widerangeof sideslopesandlongitudinaldivergencesof the basinwalls. The important parameters of the jump, such as the length, sequent depth and the rate of energy loss were computed and compared to those in the normal jumps. Tests were conducted for three different side slopes (0.5: 1, I: 1, 1.5:1) and four diverging angle (3", 5", 7; 9") with the straight jump in the rectangular section and in the wide scope of decsent numbers (trom3 to 9). The results indicate that any decrease in the side wall slQPesfor a particular angle of divergence would cause a reduction in the sequent depth and an increase in the jump length and energy loss compared to the rectangular section on the same angle of divergence. It is also found that the longitudinal divergence of the side walls for a particular side slope will increase the stability of the jump within the stilling basin. It will also cause a reduction in the sequent depth and the jump length as well as an increase in energy loss of the jump, when compared to the straight jumps in either rectangular or trapezoidal sections.

In this study, the effects of sharp-crested sill on the characteristics of hydraulic jump formed in a Gradually expanding stilling basin of rectangular cross section was investigated. The expansion of the basin is accomplished by increasing the bed width in the stream-wise direction. A total number of 228 tests were carried out for the range of initial Froude number from 3.1 to 10.3. Sills with various heights and different locations, relative to the jump toe, were installed in the basins with the diverging angles of 3, 5, and 9 degree. In all tests, the main characteristics of hydraulic jump including sequent depth ratio, relative length of jump and the relative energy loss were measured. The results indicate that installing sharp-crested sills have insignificant effect on the sequent depth ratio but may considerably decrease the length of jump. In addition, observations indicate that sills may improve general conditions and features of Gradually expanding hydraulic jump in a rectangular channel.

This study was carried out to identify the best required time for stratification along with the optimum time and generation power test of seeds. The treatments include 22 different periods of stratification from 10 to 32 days. The experiment was done as completely random design blocks with four replicate with 30 seeds within each block. The Ending time of stratification period was the same for all treatments. The percentage of rotten seeds, seed germination and rootlet length were measured, and then the obtained data were analyzed statistically. The results indicated that Chilgoza seeds incubated in temperature of 4°C for 33 days could germinate 38%. While the seeds with less than 16 days has no germination power. In general, this study suggests the period of 23-30 days as the best time for stratifying Chilgoza seeds.