Showing 17 results for Channel
S. Kouchakzadeh,
Volume 5, Issue 1 (4-2001)
Abstract
Bridge abutments are usually located in the floodplain zone of rivers where velocity and shear stress are not uniformly distributed. The influence of channel geometry and lateral momentum transfer in compound flow field on the scouring phenomenon has not been fully investigated and understood yet. The impact of lateral momentum transfer on the local scour at abutments terminating in the floodplain of a compound channel is presented in this paper.
It is shown that, by accounting for lateral momentum transfer at small floodplain/main channel depth ratios (λa/H<0.3), estimates of maximum local scour depth are increased by up to 30%. Therefore, ignoring the influence of the lateral momentum transfer, in such circumstances, might result in unrealistic estimation of the scour depth. To draw a more general conclusion, more data are required to assess the influence of different parameters affecting the phenomenon in compound flow conditions.
H. Afzalimehr,
Volume 5, Issue 3 (10-2001)
Abstract
Over the past decades, numerous regime formulations, describing channel width, average flow depth and channel slope, have been proposed for gravel-bed rivers. Using the downstream hydraulic geometry measurements from 280 field channels, nine gravel-bed predictive formulations were compared. They are attributed to Bray, Chang, Hey and Thorne, Kellerhals, Neil, Parker and Simons, and Albertson. The comparison showed that the dominant discharge and the median grain size are not sufficient hydraulic variables to predict the channel geometry (width, depth, and especially channel slope). Seeking more complex formulations with the measured parameters, it was not possible to improve the existing formulations significantly without spurious influences of common variables.
A second database is thus gathered from 19 laboratory-based boundary-layer measurements published in Kironoto and Graf (13) and Song et al. (19). In fact, the boundary-layer theory will respond to a fundamental question: are the existing available variables in literature not sufficient or the methods of their estimations are not appropriate? Based on the present study, the methods of their estimations should be changed. The second database allows proving the usefulness of the Shields parameter for the prediction of average flow depth and channel slope. Hence, using boundary-layer theory for prediction of Shields parameter and stable channel parameters is recommended.
S. Kouchakzadeh,
Volume 6, Issue 3 (10-2002)
Abstract
Side channel spillways have a common usage in conveyance and distribution networks, high dams, water and wastewater treatment plants, and surface drainage networks. A side channel carries spatially varied flow with increasing discharge and their water surface profiles is a main feature in the design process. Usually, the bottom width of the channel is flared in the flow direction and an end sill is also installed at the downstream end to provide a control section and to generate an even water surface profile. In this study, the impact of installing an end sill on the flow characteristics in a non-prismatic side channel is presented. Six distinct longitudinal profiles were clearly observed in each run and the difference between the mid points of the maximum and the minimum profiles of each run was used to evaluate the sill effects on the water surface profile and the energy dissipation.
The results indicated that the maximum and the minimum differences are, respectively, equal to critical depth and half of it generated at the channel downstream end. Also, based on an envelope of the data, a method was proposed to determine the maximum potential impact of an end sill that might have on the flow depth, which could also be considered as a guideline in the design process.
T. Honar, M. Javan, A. Keshavarzi,
Volume 6, Issue 3 (10-2002)
Abstract
Side weirs as flow diversion devices are widely used in irrigation, land drainage and urban sewage systems. In the present study, the effects of the length and height of inclined side weir crest on discharge coefficient were investigated in prismatic and nonprismatic rectangular channels.. In this study, 675 laboratory tests were conducted.
Analysis of experimental tests showed that the discharge coefficient is strongly correlated with uptream Froude number, height of weir to depth ratio at upstream of weir, ratio of water depth on weir to length of weir, and with prismatic factor. Based on experimental results, a model is proposed. The model is capable of estimating the discharge coefficient under subcritical flow conditions. Finally, the data from the proposed model was compared with those obtained by other researchers under different side and bed slopes. There was a good agreement with a relative error of less than ten percent.
A. Rezvanfar, H. Vaisy,
Volume 6, Issue 4 (1-2003)
Abstract
To improve livestock production and to modernize dairy husbandry in Iran, it is essential to disseminate the most recent information on dairy husbandry technologies and management practices through various means among farmers. An understanding of farmers’ communication behaviour is essential in formulating effective communication strategies for livestock development. For the purposes of this study, East Azarbaijan Province was selected. The study will examine how farmers obtain information on dairy husbandry technologies and management practices and how they communicate with agents of technology transfer (extensionists). The major channels and sources used in obtaining information and inter-system communication by farmers are discussed. To study the farmers’ communication behaviour, a sample of 154 farmers from a total of eight villages (four villages from high level plain areas and four villages from low level plain areas) were selected using “Stratified two-stage random sampling” method. Data were gathered by filling out questionnaires that had been tested before. The criteria like frequencies in terms of number and percentage, mean and product moment correlation were calculated. In addition, multiple regression analysis was used for the analysis of the data.
According to the findings of this study, most farmers in the two groups (98%) had low information input score. The independent variables such as information output, farmer inter-system communication, farmer-researcher communication, farmer-extensionist communication, education, family education status and availability of input facilities had positive and highly significant relationships (P<0.01) with information input.
D. Zare, A. Zomorodian, H. Ghasemkhani,
Volume 9, Issue 1 (4-2005)
Abstract
The application of solar energy for drying cereals and other agricultural commodities has been increasing lately. This is due to the fact that solar energy is free, renewable, inexhaustible and environmentally friendly. This research is a new approach for employing solar energy as the main energy source for drying purposes. The drying test rig was designed, fabricated and evaluated. The grain solar dryer is an active mixed mode type with a semi-continuous discharge system. The rig consists of six solar air collectors, a heating channel, a drying chamber and an air distributing system. Rough rice was selected as cereal grain to be dried in the dryer to evaluate the system of the drying rig. In this research the effect of mass flow rate and time of crop discharge, on the rate of crop drying were evaluated. The experiment was conducted as a factorial experiment on the basis of a completely randomized design with three replications. The first factor was mass flow rate at three levels of 0.011, 0.0066 and 0.0048 kg/m2s and the second factor was the time of crop discharge at two levels of 15 and 30 min. The dryer capacity, the amount of energy consumed (electrical and solar) during drying process, and the efficiency of collectors were also evaluated. According to Duncan's multiples range test, the effects of mass flow rate of drying air, and the interval time of discharge, were highly significant on the moisture content of discharged rough rice. The maximum efficiency of the collectors was 37.13% and the fraction of energy consumed by heating channel during the drying process, compared with solar energy, was 6-8 percent. The maximum capacity of the dryer was about 132 kg of rough rice from 11 AM to 2 PM reducing the initial moisture content from 27% to 13%. On the whole, the evaluation results indicated that the dryer could reduce the moisture content of the crop to the storage safe moisture content during appropriate time with highenergy efficiency.
S. M. A. Zomorodian, M. R. Bagheri Sabzevari,
Volume 9, Issue 4 (1-2006)
Abstract
The vertical pipe intake is an economical structure relative to the other alternatives. VPI usually installed near the water surface and prevents from the coarse sediment entrance to the system. The strong vortex in VPI entrance is a major problem which may reduce the system efficiency. Recognizing the vortex affected parameters, helping engineers to design anti vortex structures. In this study an experimental model is built to study the effect of tangential velocity, flow direction at approach channel outlet on the discharge coefficient of vertical pipe intake. By dimensional analysis it is indicated that the vortex in VPI could be defined by the dimensionless numbers (Reynolds, Weber, Froude, Circulation and Submergence). The relationship between the Froude, Circulation and Submergence numbers are presented. By using this relation one can determine the Submergence number and then calculate the discharge coefficient of vertical pipe intake.
H. Afzalimehr, M. Heidarpour, S. H. Farshi,
Volume 10, Issue 1 (4-2006)
Abstract
Suitable stable channel design and optimization of river geometry can reduce cost of projects. The regime theory provides the possibility of empirical and semi-empirical investigations of stable channel design in which erosion and sediment transport are in equilibrium. The objective of this research is an investigation and a comparison of the influence of uniform and non-uniform flows on the prediction of stable channel characteristics. The following empirical and semi-empirical (extremal hypothesis) equations were selected to study the effect of uniform flow: Lacey, Chital, Kondap and Garde, and Chang. Using 24 regime channels in USA, the statistical and graphical approaches were applied to compare and to evaluate the power of prediction of the selected equations. In order to investigate the effect of non-uniform flow structure on the stable channel characteristics, 21 measured velocity profiles in Gamasiab River were applied. Using the boundary-layer theory, shear velocity was computed for each profile. Accordingly, the estimated Shields parameter using the boundary-layer approach is the most effective parameter on the regime channel prediction. Simultaneous application of the non-uniform flow effect and the boundary-layer theory not only remove the risk of spurious correlation but also improve the estimation of stable channel characteristics.
A. A. Montazar, S. Kouchakzadeh, M. H. Omid,
Volume 10, Issue 3 (10-2006)
Abstract
The sensitivity analysis approach should be regarded as a new means which has recently been proposed for assessing flow of the irrigation networks. This approach uses the flow steady state equations and the physical conditions of irrigation channels to evaluate the response of the system to input perturbations. In this paper, some structural hydraulic sensitivity indicators were developed and utilized in studying the flow of an irrigation channel. For evaluating the efficiency of indicators and proposed analysis method, a real case was simulated by SOBEK model. Using the simulation results and introduced indicators, the flow regulation and distribution process within channel was studied. The results indicated a successful application of sensitivity indicators in evaluating system's potential in relation to alternative operational scenarios. With the calculation of these indicators, a comprehensive information system could be provided and applied in the analysis of the response potential of channel to structural perturbations, estimation of structure setting accuracy, and in the choice of suitable operation frequency there of.
M. Karami Moghaddam, M. Shafai Bajestan, H. Sedghi,
Volume 15, Issue 57 (10-2011)
Abstract
In diversion flows, a portion of stream flow which enters the intake is diverted from upstream of the intake denoted by a surface and is called dividing stream surface (DSS). The amount of flow and sediment discharge entering the intake as well as design of submerged vanes to control sediment depends on determination of dividing stream width. In this study, the experimental tests were carried out at a 30 degree water intake from a trapezoidal section. Three components of velocity data were obtained for different flow conditions. Then numerical SSIIM2 model was calibrated and verified using tests data. More flow conditions such as the main channel with rectangular section were run using SSIIM2 model to get enough hydraulic data. From analysis of these datas it was found that the dividing stream width in different distances from the bed depends directly upon the diversion flow ratio. It was found that in comparison to the rectangular section, in trapezoidal cross section, the DSS dimensions are modified in such a way that its width is increases at the surface and reduced at the bed for the same flow conditions. Relations for predicting the dividing stream width and diversion flow ratio have been presented in this paper for intake from both rectangular and trapezoidal cross sections.
K. Roshangar, R. Valizadeh,
Volume 21, Issue 2 (8-2017)
Abstract
Hydraulic jump is the most common method of dissipating water’s kinetic energy in downstream of spillways, shoots and valve. In this paper, Support Vector Machine (SVM) method, as a machine learning method, have been used to estimate hydraulic characteristics such as the sequent depth ratio, jump length and energy loss in three different sudden expansions stilling basins, and the rate of influence of input parameters in each jump has been analyzed. In order to evaluate the performance of proposed method, 936 sets of the observed data have been used for training and testing process of three kinds of expanding channel models. Furthermore, a comparison between semi-theoretical approaches and the data obtained from the best SVM models have been carried out. The results confirmed the efficiency of SVM method for estimating the hydraulic jump characteristics and proved that this method performed well in comparison to the semi-theoretical relationships. The obtained results revealed that the superior model for the sequent depth ratio and relative energy dissipation was the model with (Fr1,h1/B) parameters and the superior model for the length of hydraulic jump prediction was the model with (Fr1, h2/h1) parameters.
S. M. Seyedian, M. Karami Moghadam, Y. Ramezani,
Volume 21, Issue 4 (2-2018)
Abstract
The study of flow patterns in front of intake has been attracted the attention of researchers during the past decades to explore the mechanism of flow and sediment entry to the intake. In this study, the separation and stream tube dimensions were investigated in water intakes installed to rectangular and trapezoidal main channel. These researches were carried out with experimental and fluent models. The results of experimental and fluent models have a good conformity. It was found that, in trapezoidal main channel, the stream tube width decreases near the bed and increases near the surface and separation dimensions reduced and led to reduction of sediment entry and increase of efficiency
P. Heidari, S. Hojati, N. Enayatzamir, A. Rayatpisheh,
Volume 24, Issue 3 (11-2020)
Abstract
The objective of this study was to investigate the impact of land use change (forest and rangelands to agriculture) on some micromorphological indices of soil quality in part of Rakat watershed, southwest of Iran. Accordingly, intact soil samples from 0-15 and 15-30 cm depths were collected from the above-mentioned land uses, and microstructure, type and abundance of voids, redoximorphic features, and humic substances were compared. The results showed that in the natural forest use, most of the voids are in the form of macropores, whereas after their conversion to agriculture, these types of voids have little development. In natural rangelands uses, voids were mainly oriented channels and of macropore type, but after switching from pasture to agriculture, they were mainly of vughy type. The results showed that natural forests (27.73%) and natural grasslands (22.28%) had more abundance of voids than forest to agriculture (19.01%) and grassland to agriculture (18.62%) land uses. In both natural forests and pasture land uses, various types of iron and manganese nodules, coatings, hypo-coatings, and quasi-coatings were significantly higher than agricultural land uses.
A. Arab, K. Esmaili,
Volume 25, Issue 1 (5-2021)
Abstract
The study of floods has always been important for researchers due to the great loss of life and property. Investigation of flood bed can provide appropriate solutions to reduce this phenomenon to managers and researchers. In this research, the compound channel (with flood plain on one side of the main channel) Been paid, Therefore, two experimental models of compound channel in laboratory flume were examined by considering dimensional analysis. With the goal Investigation of lateral slope of flood wall in laboratory model In the first model, transverse slope 0 And in the second model, a value equal to 50% Was considered. Also in order to investigate the effect of longitudinal slope of river bed sediments Longitudinal slope in three steps 0.00 2, 0.004 and 0.006 Was changed. Examining the ADV speedometer data, the results showed that with increasing the longitudinal and transverse slope (slope of the flood wall) of the channel, the maximum longitudinal velocity changes to the floor of the channel. In order to investigate the effect of average sediment diameter on the scouring process during experiments Mm was used. The results showed that increasing the longitudinal and transverse slope had a great effect on increasing the volume of washed sediments 3 and 0.9 of sandy sediments with a diameter Along the canal and with the increase of these longitudinal and transverse slopes in the channel, more sediment transport volume occurs. In the following, using Investigation of dimensionless numbers obtained from dimensional analysis, dimensionless weight landing number was introduced to evaluate this value value of other hydraulic parameters and Was introduced. A relationship based on nonlinear regression with correlation coefficient Acceptable was introduced at around 0.88.
A. Moghtaderi, E. Valizadegan,
Volume 25, Issue 2 (9-2021)
Abstract
In this study, the hydraulic characteristics of the flap gates are installed at the end of the trapezoidal channels were investigated by laboratory study. In the physical model, three trapezoidal channels and four gates with different weights were used (12 gates for three channels). Based on several experiments, equations for estimating of flow rate for each side slope (each channel) were developed using dimensional analysis. In this research, five forms of discharge-stage relationship were used to obtain relationships for each side slop to estimate flow rate, separately. The results show that none of the discharge-stage relationships forms as a single relationship for all flap gates in a certain channel are suitable for estimating discharge. But the first, second, and third forms of the discharge-stage relationship are very suitable for estimating the flow rate in a certain channel for a certain flap gate. In other words, for each gate with a specific weight, a separate (unique) relationship is obtained to estimate the flow rate in the form of the first to the third discharge-stage relationship in a certain channel. To estimate of flow rate by using the first form of the discharge-stage relationship, the maximum values of statistical parameters of RMSE, ME, and MARE, among all three channels, are 0.0001 m3/s, 0.00022 m3/s, and 0.22 percent, respectively. The values of all the above statistical parameters for the first, second, and third forms of the discharge-stage relationship are presented in the article.
B. Shahinejad, A. Parsaei, A. Haghizadeh, A. Arshia, Z. Shamsi,
Volume 26, Issue 3 (12-2022)
Abstract
In this research, soft computational models including multiple adaptive spline regression model (MARS) and data group classification model (GMDH) were used to estimate the geometric dimensions of stable alluvial channels including channel surface width (w), flow depth (h), and longitudinal slope (S) and the results of the developed models were compared with the multilayer neural network (MLP) model. To develop the models, the flow rate parameters (Q), the average particle size in the floor and body (d50) as well as the shear stress (t) as input and the parameters of water surface width (w), flow depth (h), and longitudinal slope (S) were used as output parameters. Soft computing models were developed in two scenarios based on raw parameters and dimensionless form independent and dependent parameters. The results showed that the statistical characteristics in estimating w, the best performance is related to the MARS model, whose statistical indicators of accuracy in the training stage are R2 = 0.902, RMSE=1.666 and in the test phase is R2 = 0.844, RMSE=2.317. In estimating the channel depth, the performance of both GMDH and MARS models is approximately equal, both of which were developed based on the dimensionless form of flow rate as the input variable. The statistical indicators of both models in the training stage are R2 » 0.90, RMSE » 8.15 and in the test phase is R2 » 0.90, RMSE = 7.40. The best performance of the developed models in estimating the longitudinal slope of the channel was related to both MARS and GMDH models, although, in part, the accuracy of the GMDH model with statistical indicators R2 = 0.942, RMSE = 0.0011 in the training phase and R2 = 0.925, RMSE = 0.0014 in the experimental stage is more than the MARS model.
B. Shahinejad, A. Parsaei, H. Yonesi, Z. Shamsi, A. Arshia,
Volume 26, Issue 4 (3-2023)
Abstract
In the present study, the flow rate in flues containing lateral semi-cylinders (SMBF) was simulated and estimated under free and submerged conditions using back vector machine models (SVM), spin multivariate adaptive regression (MARS), and multilayer artificial neural network (MLPNN) model. In free flow mode, the dimensionless parameters extracted from the dimensional analysis include the ratio of upstream flow to throat width and contraction ratio (throat width to channel width), and in the submerged state, in addition to these two parameters, the depth-to-throat width, and bottom-depth parameters upstream depth were used as input and the two-dimensional form of flow rate was used as the output of the models. The results showed that in free flow mode in the validation stage, the MARS model with statistical indices of R2 = 0.985, RMSE = 0.008, MAPE = 0.87%, and the SVM model with statistical indices of R2 = 0.971, RMSE = 0.0012, MAPE =1.376%, and MLPNN model with statistical indices of R2 = 0.973, RMSE = 0.011, MAPE = 1.304% have modeled and predicted the flow rate. In the submerged state, the statistical indices of the developed MARS model were R2 = 0.978, RMSE = 0.018, MAPE = 3.6%, and the statistical indices of the SVM model were R2 = 0.988, RMSE = 0.014, 2%. MAPE = 4, and the statistical indicators of the MLPNN model were R2 = 0.966, RMSE = 0.022, and MAPE = 5.7%. In the development of SVM and MLPNN models, radial kernel and hyperbolic tangent functions were used, respectively.
