Showing papers in "ISH Journal of Hydraulic Engineering in 2015"
TL;DR: In this paper, an attempt has been made to relate the fluctuation of groundwater level with hydrogeological factors, including geomorphology, geological structures, geological formations, soil types, and elevation.
Abstract: Due to rapid industrialization and increase in human population, there has been a tremendous pressure on the water resources. In hardrock terrain, the availability of groundwater is confined to fracture and weathered zones. In the present study, the study area is Dhanbad district of which most of the parts lie on hardrock terrain. In this study, an attempt has been made to relate the fluctuation of groundwater level with hydrogeological factors. The various hydrogeological factors that have been considered here which can affect the aquifer recharge are geomorphology, geological structures, geological formations, soil types, and elevation. These hydrogeological factors have been analyzed for 65 monitoring wells and frequency plots between different hydrogeological parameter classes, and water level fluctuation have been used to assess the relative impact of different hydrogeological subclasses on aquifer recharge. Further statistical analysis has been done for all hydrogeological parameters for each subcla...
43 citations
TL;DR: A detailed review of the most commonly used models which are suitable for the estimation of moisture uptake by plants in different agro-climatic regions is presented in this paper, where an effort has been made to compare the performance of di...
Abstract: Estimation of root water uptake and water movement in plants is crucial to quantify transpiration and hence the water exchange between land surface and atmosphere through plants. Present paper is aimed to illustrate and discuss how mathematical modeling can be used for understanding of plants and, in particular, plant–soil interactions. Soil water movement due to root water uptake is a key process for plant growth and transport of water in the soil plant system. There are different root water uptake models which can be used for estimation of moisture uptake by plants. The accuracy of moisture uptake prediction by plants depends on selection of proper mathematical models. Root uptake models are available in different forms i.e. linear, nonlinear, and exponential. In this paper, a detailed review of the most commonly used models which are suitable for the estimation of moisture uptake by plants in different agro-climatic regions is presented. Further, an effort has been made to compare the performance of di...
30 citations
TL;DR: In this paper, numerical simulation of flow over an aerator on a deep-seated orifice spillway is presented. But, no systematic work has been reported for aerators on orifices.
Abstract: Orifice spillways are provided in dams situated in hilly regions for carrying out dual function of passing the flood and flushing of sediments. Aerators are required on these spillways for mitigating cavitation damage for head over spillway exceeding 50 m. The available current literature describes mainly the investigations for aerators on overflow spillways and no systematic work has been reported for aerators on orifice spillways. Traditionally, physical model studies have been used for designing the aerators on overflow spillways. However, extensive experimentation with sophisticated instrumentation is required to understand the flow field comprising pressure and velocity distribution and air entrainment characteristics. Numerical modelling using computational fluid dynamic techniques provides a complete picture on flow field in the vicinity of aerator. This study describes numerical simulation of flow over an aerator on deep-seated orifice spillway. The two-phase three-dimensional (3D) numerical model...
21 citations
TL;DR: In this paper, a carefully controlled extensive experimental investigation of the effect of mutual interference of a group of two bridge piers of unequal sizes placed in tandem arrangement at varied pier spacing under steady, uniform flow clear water scour conditions on scour hole characteristics was conducted.
Abstract: The work reported herein is concerned with a carefully controlled extensive experimental investigation of the effect of mutual interference of a group of two bridge piers of unequal sizes placed in tandem arrangement at varied pier spacing under steady, uniform flow clear water scour conditions on scour hole characteristics. The data on various characteristics of scour holes developed around the piers are collected and analyzed. Present study reveals considerable mutual interference effect on scour hole characteristics which may lead to bridge failure, if pier group effect is ignored and bridge piers are designed merely as an isolated pier.
14 citations
TL;DR: In this article, a hybrid finite volume method is used to solve the governing equations for solute concentration in mobile region and the behavior of breakthrough curves in mixed heterogeneous soil column experiments.
Abstract: In this paper, we investigate the behavior of breakthrough curves in mixed heterogeneous soil column experiments. Advective dispersive transport equations are used for solute transport through mobile–immobile porous medium. A hybrid finite volume method is used to solve the governing equations for solute concentration in mobile region. In first part of the study, constant dispersion, linear, and asymptotic distance-dependent dispersion functions are used to describe the scale effect and to simulate experimental breakthrough curves observed in long soil column experiment. Also, a comparative study has been done among distance-dependent and constant dispersion models, while simulating the experimental data of solute transport through soil column with constant mass transfer coefficient. In second part of the study, variable mass transfer coefficient as function of pore velocity and travel distance is considered and an empirical relation is derived from observed data from experiments. It is shown that asympto...
12 citations
Abstract: The prediction of ocean currents on real time basis is a complex exercise due to the variability of coastal features like topography and bathymetry as well as uncertainty of driving forces and also interaction among various met-ocean parameters. Although numerical methods are commonly used for this purpose, they need large and detailed exogenous information along with high computational resources and at times can have less tolerance to noise and gaps in data. At this backdrop and when site-specific information is sought for, data-driven techniques like artificial neural network (ANN) might appear attractive. Although there are some past applications of ANN to online current forecasting, lower prediction accuracy at higher values and over longer prediction intervals together with unequal accuracy levels for zonal and meridional current components have remained as problems. This paper attempts to address these issues. At two locations in North Atlantic and North Pacific Oceans the ANN-based time series mode...
11 citations
TL;DR: In this article, a cylindrical weir-gate was used to quantify the behaviour of germane factors on discharge coefficient variation of combined-free over-under flow on a cylinder-weir gate, and the Buckingham Phi theorem was employed to correlate the discharge coefficient to the effective dimensionless hydraulic and geometrical arguments.
Abstract: This experimental work endeavours to quantify the behaviour of the germane factors on discharge coefficient variation of combined-free over-under flow on a cylindrical weir-gate. The experiments were carried out on varied geometrical dimensions of the weir-gate under hydraulic conditions of over, combined and under flows. The Buckingham Phi theorem was employed to correlate the discharge coefficient to the effective dimensionless hydraulic and geometrical arguments. Meaningful contribution of the ratios of (a/D), (yup/yd), (Hw/D) and Frup in variation of Cds were found. The Cds ranged between 0.6 and 1.2 with average value of 0.89 for combined over-under flow, which indicates larger values of Cds were recorded, in comparison with under flow. The developed empirical relationships for over, combined and under flows presented good coincidence with experimental results within the limitations of the runs.
11 citations
TL;DR: In this article, the boundary and the depth of aquifers in the western part of greater Kushtia district, Bangladesh were delineated using geoelectrical sounding data.
Abstract: Geoelectrical sounding, borehole litholog, and groundwater data have been used for the exploration of groundwater resources in the western part of greater Kushtia district, Bangladesh. This study aimed to delineate the boundary and the depth of aquifers, and assess their vulnerability to near-surface contaminants. Fourteen geoelectrical sounding data are interpreted and the corresponding geoelectrical logs are correlated with the available nearby horehole lithologs. Four distinct geoelectrical layers are identified within the depth of 105 m, namely thin topsoil (8.0–97.6 Ωm, 0.5–3.6 m), conductive clay-silt-sand layer (8.6–27.5 Ωm, 1.3–49.4 m), medium resistive fine grained aquifer (25.8–45.0 Ωm, 10.1–30.4 m), and high-resistive coarse grained water-bearing aquifer (35.0–64.9 Ωm, 30.0–76.9 m). The shallow aquifer (third layer) is found to occur at a depth ranging between 1.7 and 51 m, whereas the deeper aquifer (fourth layer) is found to occur within the depth between 14 and 52 m, both saturated with wate...
11 citations
TL;DR: In this article, the effect of porcupines on the velocity of flow and their ability to capture sediment has been investigated experimentally, and an attempt has been made to logically study the pattern of deposition caused by various configurations of Porcupine field layout and hence to propose a preliminary design methodology.
Abstract: Problems of river bank and in-stream erosion are very common in most of the rivers in India and abroad. Various attempts have been made to overcome excessive erosion by constructing river training works. Porcupine systems are one of the novel techniques which have been adopted as a cost-effective method of river training. In this paper, the effect of porcupines on the velocity of flow and their ability to capture sediment has been investigated experimentally. Also, an attempt has been made to logically study the pattern of deposition caused by various configurations of Porcupine field layout and hence to propose a preliminary design methodology. Results show that there is a considerable reduction in the flow velocity resulting in the deposition of sediment with porcupines offering resistance to flow.
11 citations
TL;DR: In this article, the authors deal with estimation of missing daily rainfall values at 11 rain gauge stations in Pune District of India using soft computing technique of artificial neural networks and by coefficient of correlation weighing method.
Abstract: Precipitation is a major factor controlling the hydrology of a region. It has been experienced that the precipitation data are sometimes lost by virtue of instrument malfunctioning, human error(s), climatic conditions which becomes an impediment in the hydrologic and hydraulic designs where rainfall series is a major input. Such missing values could be retrieved using estimated value by employing a large number of conventional hard computing techniques such as normal ratio method, inverse distance value method to name a few. The present work deals with estimation of missing daily rainfall values at 11 rain gauge stations in Pune District of India using soft computing technique of artificial neural networks and by coefficient of correlation weighing method. According to the correlations of averages of all stations, different groups comprising of 3–4 stations each were formed. Models were developed for each group to estimate daily rainfall values at any one station as output while data of other stations in ...
11 citations
TL;DR: The applicability and performance of the so-called M5 model tree machine-learning technique show that MTs, being analogous to piecewise linear functions, have certain advantages compared to ANNs – they are more transparent and hence acceptable by decision-makers, are very fast in training and always converge.
Abstract: Discharge measurement in rivers is a challenging job for hydraulic engineers. A graph of stage vs. discharge represents the stage–discharge relationship, also known as rating curve. Once a relationship is established, it can be used for prediction of discharge from stage. For various hydrological applications, the accurate information about flow value in rivers is very important. In this paper, the stage–discharge relationship is modelled using three different data-driven techniques, namely non-linear regression (NLR), artificial neural networks (ANN) and model tree (MT). Artificial intelligence technique like ANN allows knowledge processing and can be used as forecasting tool. The applicability and performance of the so-called M5 model tree machine-learning technique show that MTs, being analogous to piecewise linear functions, have certain advantages compared to ANNs – they are more transparent and hence acceptable by decision-makers, are very fast in training and always converge. In the present work, it was seen that the accuracy of M5 trees is at par with ANNs and both were better than NLR.
TL;DR: In this paper, the authors present a comprehensive review of these studies and present a detailed analysis of the changes associated with the presence of fine sediment in flow in a river, including viscosity and density, resistance to flow, bed load carrying capacity, etc.
Abstract: Fine sediments that join rivers from various channel and non channel sources considerably affect on the hydraulics of the river. The hydraulics of river carrying water with fine sediment has a different fluid and flow characteristics as compared to that carrying clear water. Basic fluid properties like viscosity and density and flow properties like resistance to flow, bed load carrying capacity, etc. are affected by the presence of fines in suspension. Several studies have been carried out to understand the changes associated with the presence of fine sediment in flow. The present paper presents a comprehensive review of these studies.
TL;DR: In this paper, the authors reviewed many of these aspects to understand the various environmental impacts of suspended sediment on river health, flora and fishes, all are part of food chain of river biota, any detrimental effect on any of these components of the food chain misbalances the entire riverine ecosystem.
Abstract: Fine sediments enter into the river through various sources such as channel bed, bank, and catchment. It has been regarded as a type of pollution in river. Fine sediments present in a river have a significant effect on river health. Benthic micro-organism, plants, and large fishes, all are part of food chain of river biota. Any detrimental effect on any of these components of food chain misbalances the entire riverine ecosystem. Numerous studies have been carried out on the various environmental aspects of rivers considering the presence of fine sediment in river flow. The present paper critically reviews many of these aspects to understand the various environmental impacts of suspended sediment on river health, flora and fauna.
TL;DR: In this paper, experimental investigations have been done to analyze turbulent flow in curved sand bed mobile channel, and measures of turbulent statistics were analyzed for its impending effect on sediment transport, the friction factor and Taylor microscale have been found to decrease with respect to depth.
Abstract: Experimental investigations have been done to analyze turbulent flow in curved sand bed mobile channel. Measures of turbulent statistics were analyzed for its impending effect on sediment transport. The friction factor and Taylor microscale have been found to decrease with respect to depth. The lower value of von Karman constant has been found for mobile bed channel. Third-order statistics, which shows the skewness and diffusion behavior, has been also analyzed for mobile bed channel. Analysis of bursting events shows that sweep and ejection are the main events for sediment transport.
TL;DR: In this article, a one-dimensional numerical analysis on multispecies radionuclide transport in a single-horizontal coupled fracture-matrix system has been performed.
Abstract: A one-dimensional numerical analysis on multispecies radionuclide transport in a single-horizontal coupled fracture-matrix system has been performed. Analysis considering linear and nonlinear adsorption cases with linear, Langmuir, and Freundlich adsorption models has been carried out. The results indicate that there is a significant change in the spatial distribution of radionuclides in a coupled fracture-matrix system when a nonlinear adsorption isotherm is considered as compared to the simplified linear sorption isotherm. Sensitivity analysis of Langmuir constant and Freundlich exponent has been performed, and the numerical results indicate that the behavior of radionuclide transport is strongly influenced by these nonlinear sorption isotherm parameters. In addition, an attempt has been made to consider the variation of fracture aperture thickness along its flow direction by introducing logarithmic distribution. A clear distinction in the spatial distribution of radionuclide concentration was observed ...
TL;DR: In this paper, a numerical model is developed for analyzing the influence of sorption intensities on velocity, macro-dispersion coefficient and dispersivity using the method of moments, and Implicit finite difference numerical technique has been used to solve the coupled non-linear-governing equations.
Abstract: Sorption is one of the key processes that play a major role in the transport of contaminants in fractured porous media. While Freundlich adsorption isotherm has been studied extensively in fractured porous media, limited studies have been conducted using Langmuir sorption. To address this issue, a numerical model is developed for analysing the influence of sorption intensities on velocity, macro-dispersion coefficient and dispersivity using the method of moments. Implicit finite difference numerical technique has been used to solve the coupled non-linear-governing equations. A varying grid is adopted at the fracture and rock matrix interface to capture the mass transfer at the interface. Results suggest that for relatively higher sorption capacities and distribution coefficients, the effective solute velocity as well as the retardation factor clearly becomes a non-linear function of time. The higher magnitude of second spatial moments for the cases of higher sorption capacities and distribution coefficien...
TL;DR: In this article, a mathematical model for describing the spatial and temporal distribution of concentration of a radionuclide chain in a saturated subsurface system is presented, where the transport of radions occurs by advection and hydrodynamic dispersion.
Abstract: Given the diminishing non-renewable energy resources and limited progresses achieved in the renewable energy sectors in India, the existing data projects that nuclear power can play a significant role in sharing the burden of meeting the growing energy demand. Low-, medium-, and high-level radioactive wastes generated from such nuclear power plants are to be disposed safely in the subsurface geological formation with the least environmental impact. In this context, a mathematical model for describing the spatial and temporal distribution of concentration of a radionuclide chain in a saturated subsurface system is presented. The transport of radionuclides occurs by advection and hydrodynamic dispersion, while diffusive transport of radionuclides takes place from mobile into immobile water zone, in a direction, normal to the direction of fluid flow. For decay of radioactive species within fracture and rock matrix, the ingrowth of daughters is considered. In addition, unlike earlier models, the present mathe...
TL;DR: In this article, two multi-variable regression models have been developed to predict discharge and approach velocity coefficients from relevant independent variables, such as the gauged head at the head measurement section, floodplain depth, length of throat in the direction of flow and cross-section geometry at the control section.
Abstract: In this paper, two multi-variable regression models have been developed to predict the discharge and approach velocity coefficients from relevant independent variables. The regression models are developed based on relevant experimental data obtained from testing nine different flow measurement long-throated flumes with symmetrical rectangular compound cross-sections. The long-throated flume was used in the compound cross-section to experimentally estimate the discharge and approach velocity coefficients using mainly head measurements and cross-section dimensions as required by the stage-discharge equations. The independent variables used in predicting the two coefficients represent dimensionless parameters defined using the gauged head at the head measurement section, floodplain depth, length of throat in the direction of flow, and cross-section geometry at the control section. Several statistically-based analyses were performed to verify the reliability of the developed multi-variable regression models. ...
TL;DR: The proposed GSA approach has good potential for a reliable and cost-effective design of canals and pseudo-weight vector approach is adopted to assist in decision-making and demonstrate its applicability for arriving at a suitable decision.
Abstract: In this study, the performance of a recent meta-heuristic technique, namely, gravitational search algorithm (GSA) is evaluated for a deterministic as well as for a probabilistic design of canals that have cross-sectional shape of horizontal bottom and parabolic sides (HBPS). The uncertainty in various input parameters is modeled using probabilistic approach and a modified chance-constrained model is presented for an optimal design of HBPS canals with the aim of minimizing the total cost, while satisfying the basic flow constraints and reliability constraints on the canal capacity and overtopping. First, the GSA method is applied to solve the HBPS canal design problem under different constraints, and its performance is evaluated by comparing with the solutions of the deterministic models by the particle swarm optimization and genetic algorithm. Then, the GSA is applied to obtain the solution of the probabilistic model and in view of multiple conflicting goals; pseudo-weight vector approach is adopted to as...
TL;DR: Jain et al. as mentioned in this paper investigated the parameters of two-point hedging policy for operating a storage reservoir and found that the policy can improve the performance of the storage reservoir.
Abstract: This paper is about the discussion of “Investigating parameters of two-point hedging policy for operating a storage reservoir”; Sharad K. Jain (ISH Journal of Hydraulic Engineering, 2014, vol. 20, ...
TL;DR: In this article, the applicability of log law is analyzed above the vegetated canopy in a tilting flume with bed covered by artificial vegetation and arranged in a regular staggered configuration.
Abstract: Experimental investigation has been done to access turbulence characteristics just above the sparse flexible submerged vegetation zone in open-channel flow. The experimentation has been done in a tilting flume with bed covered by artificial vegetation and arranged in a regular staggered configuration. The applicability of log law is analysed above the vegetated canopy. Turbulent parameters such as velocity profiles, Reynolds stresses, turbulent intensities, quadrant analysis, turbulent production and diffusion, dissipation and stream power have been appraised to understand the hydrodynamics of vegetated channel. Results show that the log law is valid above the canopy of submerged vegetation with decreased Von-Karman constant. Maximum value of turbulent intensities and Reynolds stresses has been found above the canopy. Quadrant analysis shows that sweeps and ejections events are more dominating factors in submerged vegetated channel.
TL;DR: In this paper, an attempt has been made to characterize the hydrodynamic regime around the coastal waters of Goa for a pre-monsoon season, using MOHID, a two-dimensional finite volume model.
Abstract: Attempt has been made to characterize the hydrodynamic regime around the coastal waters of Goa for a pre-monsoon season, using MOHID, a two-dimensional finite volume model. The numerical model was forced with tides at open boundaries and calibrated using measured water levels and currents, during pre-monsoon season. The modeled water levels and currents were compared with field observations and found to be satisfactory, with correlation of 0.97 for water levels, 0.79 for zonal currents, and 0.84 for meridional currents. The ratio of diurnal (O1, K1) and semidiurnal (M2, S2) constituents was 0.63, suggesting that tides in this region are mixed, mainly semidiurnal in nature. The variation in amplitude of tidal constituents from the open boundary to the mouth and upstream of the Mandovi and Zuari estuaries has been modeled and compared with previous field studies and found to be satisfactory. The details of numerical scheme, methodology, and results are discussed in this paper.
TL;DR: In this article, the effect of convergent angle on the non-uniform flow through porous media was studied in a converging permeameter, and the relationship between Hydraulic Gradient (I) and Froude Number (FK2) was presented.
Abstract: The effect of convergent angle on the non-uniform flow through porous media was studied in a converging permeameter. The scope of the present paper is to present the relationship between Hydraulic Gradient (I) and Froude Number (FK2) for flow through porous media with converging boundaries, using intrinsic permeability (K) as characteristic length, and to also show pictorically the relation between linear parameter, a, and non-linear parameter, b, in terms of Media Constant (CW). In the present case, McCorquodale data of size 1.66 cm was used as media, to develop theoretical curves using friction factor (FK) and Reynolds number (RK) relationship, and verified with the help of existing experimental data of different convergent angles.
TL;DR: In this paper, the authors investigated the impact of sediment ingestion on the dimensions of the trench weir and found that the trajectory of the sediment movement and stream lines of flow are different due to different inertia and for the minimization of entry of sediment into the trench, the clear opening length should be less than the jumping length of the particles.
Abstract: Trench weirs are commonly constructed across boulder rivers. Such weirs have definite advantages, as they do not obstruct the flow of the river, but susceptible to ingestion of bed load sediment having size smaller than clear opening of the rack into the trench. This study deals with the experimental study of the mechanics of movement of sediments, over and across the racks and also quantification of the sediments ingested/trapped into the trench, which shall be useful for fixing the dimensions of the trench weir for minimum ingestion of sediment. This study reveals that the trajectory of the sediments movement and stream lines of flow are different due to different inertia and for the minimization of entry of sediment into the trench, the clear opening length shall be kept less than the jumping length of the particles. For ratio of size of sediment to clear spacing of rack less than 0.75, the total incoming sediment is ingested into the trench. However, for ratio greater than 0.75, the ingested sediment ...
TL;DR: In this paper, an experimental investigation on measurement of 3-D instantaneous velocity profiles in a mobile boundary channel with uniform and non-uniform sediments is reported, where the estimated velocity fluctuations from measured velocity profiles along the center line of the flume are used to quantify the nature of bursting events, and turbulence characteristics on uniform (finer and coarser) and nonuniform sediment.
Abstract: An experimental investigation on measurement of 3-D instantaneous velocity profiles in a mobile boundary channel with uniform and non-uniform sediments are reported. The estimated velocity fluctuations from measured velocity profiles along the center line of the flume are used to quantify the nature of bursting events, and turbulence characteristics on uniform (finer and coarser) and non-uniform sediments. The analysis presented in the paper indicated that sediment characteristics play very significant roles for existence of aforesaid characteristics (turbulence characteristics and bursting events) near the channel beds and fluid flow regions in the main flow. Further investigations on aforesaid theme are recommended, while taking the measurements on velocity profiles along the depths across the channel width including the center line depth of the channel.
TL;DR: In this article, a simple mathematical solution for sharing of discharges at a bifurcation considering simple hydraulic equations like equation of continuity, Chezy's equation, conservation of momentum, etc.
Abstract: The present study deals with a simple mathematical solution for sharing of discharges at a bifurcation considering simple hydraulic equations like equation of continuity, Chezy’s equation, conservation of momentum, etc. Finally, theoretical models for prediction of discharges through the bifurcated channels as a function of radius of curvature, slope, bifurcation angle, velocity of flow, etc. have been developed. A series of physical model studies simulating a typical bifurcation on river Kasai in West Midnapur district in West Bengal have also been conducted on a movable bed model at River Research Institute, Haringhata, West Bengal, India. The theoretical model was found to compare well with recently observed prototype data and physical model test results.
TL;DR: In this article, a numerical model using finite volume QUICK scheme has been developed for simulating the transport behavior of solutes in a coupled fracture-matrix system for pulse-type boundary condition as against the conventional constant continuous source type boundary condition, which essentially reflects the reality better.
Abstract: A numerical model using finite volume QUICK scheme has been developed for simulating the transport behavior of solutes in a coupled fracture–matrix system for pulse-type boundary condition as against the conventional constant continuous source-type boundary condition, which essentially reflects the reality better, as it is practically not feasible for any source type to discharge it continuously with the same magnitude for a very long period. The sensitivity of fracture and rock matrix parameters, namely fracture aperture thickness, matrix porosity, and matrix diffusion coefficient have been analyzed under this complex boundary condition. In addition, the role of nonlinear sorption as well as decay has also been investigated. Numerical results suggest that the reduction in relative concentration within the fracture resulting from pulse-type boundary condition should always not be mistaken for matrix diffusion. It has been concluded from the present numerical study that segregating and quantifying the role...
TL;DR: In this paper, an empirical, non-linear, multivariable regression model for predicting discharge in smooth asymmetric compound rectangular channel is presented. The model is developed using experimental discharge data generated from testing nine different channel cross-sections with varied geometric dimensions.
Abstract: This paper presents an empirical, non-linear, multivariable regression model for predicting discharge in smooth asymmetric compound rectangular channel. The model is developed using experimental discharge data generated from testing nine different channel cross-sections with varied geometric dimensions. The predictive strength of the developed regression model is validated using several major statistics. All deployed statistics have indicated that the developed model is highly significant. In addition, the area method has been used to validate the model’s discharge predictive strength. The area method predicts discharge mainly based on the cross-section geometry and apparent shear stress. As obtained from the literature, a sample of three different regression-based models has been used to estimate the apparent shear stress. Therefore, three different sets of discharge have been predicted using the area method. The four sets of discharge predicted using the developed regression model and area method have been compared to their corresponding experimental values using the sum of squared errors (SSE). The outcome is that seven channel cross-sections out of nine tested ones resulted in minimum SSE values when discharge predicted using the developed regression model.
TL;DR: In this paper, the effect of free surface confinement on the flow features of turbulent jets was investigated and the results showed that the behavior of the jet under the influence of the limited free surface depth will remain unaltered.
Abstract: The investigation deals with the effect of the free surface confinement on the flow features of turbulent jets. Of the alternate techniques available to express the distribution of the axial velocity across the jet, the authors chose to follow the formulae of Lee et al. given in their list of references. Other simpler methods, having a theoretical background, are also available in the literature to unify the velocity distribution in the establishing and the established zones (Pani 2012). Notwithstanding the formulae selected for representing the experimental findings of the authors, the behavior of the jet under the influence of the limited free surface depth will remain unaltered. The Reynolds number of flow for the three sets of runs lies in the range 2.12 × 10–4.25 × 10, which is fairly high. Hence, the experimental results are expected to be independent of the jet velocity. In contrast, three efflux velocities, 4.24, 7.0, and 8.5 m/s, were used in the experiments and many of the plots of the experimental data are seen to be velocity dependent. This could be a consequence of the limitations of the experimental setup. The length of the test tank L/D = 50 and the downstream wall is too close to the farthest section of the jet where velocities were recorded. When the velocities are high and the submergence is low, the free surface can distort and a strong recirculation zone could exist and zeropressure gradient will not prevail. This can alter the features of the flow significantly and the measured values of the velocity profiles would deviate from the classical case. No mention has been made about this aspect. The location of the outlet pipe close to the bottom of the tank may create a curved flow. For steady condition of flow, the inflow equals the outflow, whereas at x/D = 30, the measured volume flux in the forward direction is 10–11 times the inflow. One would therefore expect that near the tail-end of the tank, the behavior of the jet will be very different than the classical circular jet. Such a feature was observed in the simulation of head-loss in man-holes. The velocity measurements were carried out with a 7 mm diameter Pitot tube. What kind of a manometer was used and what was the accuracy of measurement, especially in measuring the velocities near the edge of the jet? Were the measurements repeatable? The authors have mentioned about the deviation of the path of a confined jet compared to the free jet without telling whether the trajectory dips or rises in the direction of flow. A similar feature was observed by Raiford and Khan (2009) while conducting experiments on confined jets. In the results and discussion section of the authors, it has been said that the decay of the jet centerline velocity is higher under the influence of the surface confinement. This seems to be grossly in error and it can be theoretically shown that in the far field, the centerline velocity is higher compared to the conventional free circular jet under zero-pressure gradient conditions. Thus, the decay of the centerline velocity in case of a confined jet should be somewhat lower. This aspect has been experimentally observed as well by Raiford and Khan. The results shown in Figure 3 are therefore difficult to accept as the experiments conducted by the authors are very similar to those of Raiford and Khan. When surface confinement effects show up, the ratio Ue/Uc should dip rather than rise from the classical straight-line relation. Based on the point-source technique and the principle of superposition, it has been proven in the past (Pani 2012) that the momentum flux on the jet centerline is
TL;DR: In this paper, the authors discuss multivarible regression models for prediction of discharge and approach velocity coefficients in flow measurement flumes with compound cross-section, with a focus on the multivariable regression model.
Abstract: This paper is about the discussion of “Multivarible regression models for prediction of discharge and approach velocity coefficients in flow measurement flumes with compound cross-section”; I Al-K