Estimation of open channel bed roughness is a topic of continued interest. Many research works ha... more Estimation of open channel bed roughness is a topic of continued interest. Many research works have been done on open channel bed resistance. Depending upon the bed conditions of the open channel, Mannings' roughness coefficient, velocity of flow, depth of flow, Froude's number and other flow parameters varies. In this study the modeling of the effect of flow parameters on the estimation of bed roughness for various bed condition has been proposed. Key Words: Mannings' roughness coefficient , velocity of flow, depth of flow, Froude's number and bed roughness.
Leakage in the water distribution network at fault location incurring huge loss of scarce water r... more Leakage in the water distribution network at fault location incurring huge loss of scarce water resource is a serious point of concern. Assam is a flood-prone State, with heavy downpour in the catchment area of the mighty Brahmaputra. Guwahati, the capital of the State experience regular flash flood with incessant spells of heavy showers every year during rainy season. During no-flow timing, due to hydraulic gradient, pathogen and other contaminants may enter the submerged distribution network. Assam currently tops in the list of Infant Mortality Rate(IMR) in India, where water-borne disease considered to be a prime factor. Hence, under this study an effort has been made to develop models for locating the faults or leakage points in the water distribution networks for Greater Guwahati City. In this paper, Based on specific field study of 29 Piped Water Supply Schemes in and around Guwahati City, models have been developed with statistical linear regression method for location of fau...
The distribution of velocity in an open channel is not uniform due to the presence of free surfac... more The distribution of velocity in an open channel is not uniform due to the presence of free surface, the bed material of the channel, the discharge, the slope of the channel etc. A number of experiments have been done for three different bed materials with different discharges. The bed materials are the original bed material i.e. smooth iron bed, grass carpet and PVC. Velocity at different sections and different depths are taken with the help of pitot tube. From the experiment, it is found that the maximum velocity appears to occur at the free surface of the channel, and the average velocity for all the cases is coming almost 0.75 to 0.95 of the surface velocity.
Open channel flow resistance is a topic of continued interest. Many works have been done on the r... more Open channel flow resistance is a topic of continued interest. Many works have been done on the resistance of flow in open channel. The three co-efficients, namely Chezy’s co-efficient, Manning’s co-efficient and Darcy’s co-efficient are generally used in the calculation of flow resistance in open channel. In this paper an attempt has been made to study the various research works done to study the effect of different flow, channel and bed conditions on open channel flow resistance. The research works are done considering the three coefficients and also under different bed conditions.
Most of the rivers have cross sectional geometry of a compound section where a deep main channel ... more Most of the rivers have cross sectional geometry of a compound section where a deep main channel is bounded by shallow adjacent floodplains. Suitable estimation of discharge in compound channels is truly necessary for the design, operation and maintenance of the channels, utmost to prediction of flood. Generally compound channels have been analyzed by dividing the compound cross-section into relative sub-areas which are easier to analyze. In this paper the traditional one dimensional (1-D) method for estimating discharge capacity of straight compound channels are reviewed and applied to overbank flows in straight fixed compound channels. The predictive accuracy of these formulae was analysed by developing software using MATLAB with the help of experimental data obtained from the compound channel section of University of Birmingham. The accuracy of these methods to predict the total cross-section discharge is evaluated.
1M.Tech, student, Dept. of Civil engineering, ADTU, Guwahat, Assam , India 2Professor, Dept. of C... more 1M.Tech, student, Dept. of Civil engineering, ADTU, Guwahat, Assam , India 2Professor, Dept. of Civil engineering, ADTU, Guwahati, Assam , India ---------------------------------------------------------------------***--------------------------------------------------------------------Abstract – A compound channel consists of the main channel and flood plain. Bed resistance for main channel and flood plain are quite different. Here, proper prediction for flood in a compound channel the proper estimation of resistance is very important. Generally a composite resistance is estimated which depends on the resistance of the main channel and flood plain. Here, under this study the composite resistance predictions by different investigation have been compared with actual resistance value in case of a straight rectangular compound channel. Different investigated has found different formula for composite resistance. The percentage error for different resistance of composite formula has been c...
The water quality based on seasonal distribution pattern of physio-chemical characteristics of th... more The water quality based on seasonal distribution pattern of physio-chemical characteristics of the river Nambul flowing in heart of Imphal city were analysed during different years before and after onset of rain. The physio-chemical parameter of water such as water temperature, pH, Turbid ity, Dissolved Oxygen, BOD, Conductivity, Hardness, Alkalinity, COD, TDS, Chloride, Calcium and Magnesium were analysed. Water samples were collected from six sampling sites. Most of the parameters were not within the permissible value of drinking water. Turbidity was higher than normal limit and alkalin ity decreased through years. BOD and COD was much lesser in upstream than the downstream. The study suggest untreated domestic, disposal from market and household to the water body causes heavy pollution in river Nambul.
A compound channel is channel whose law is governed which mainly occurs in rainy season. In a Com... more A compound channel is channel whose law is governed which mainly occurs in rainy season. In a Compound channel with main channel and flood plains have been considered where exchange of momentum occurs, due to the presence of different vegetation in the bed channel, examples:rivers. In this paper all the research works has been reviewed with all the searched papers are of flows in compound channel. Such a review will help in enhancing the understanding for improving different conveyance and flow resistance in the field. Vegetation exists on the floodplains of almost all natural channels. Researchers have suggested equations for estimating composite roughness of an open channel flow which are good for simple channels and do not incorporate the interaction mechanisms that exist in a compound channel.
Leakage in distribution network accruing huge loss of coveted, depleting water resource has becom... more Leakage in distribution network accruing huge loss of coveted, depleting water resource has become a serious concern of water Engineers and planners. The National Rural Drinking Water Programme (NRDWP) guidelines of the Ministry of Drinking Water and Sanitation, Government of India, effective f rom April, 2009, stipulates 15% transmission loss, while the Min istry, by its communicat ion No F-11014/1/2015-Water-II-Part(5) dated 1st April, 2016, quotes media reports that 50% potable drinking water gets wasted because of leakages before it reaches the consumer and asked for, all the States to adopt suitable measures to check leakage in the condition of growing drinking water shortage, because of erratic monsoon and contaminated water in many region s. Guwahati, the second largest Metropolitan region in eastern India, next to Kolkata, gets heavy spells of rain during rainy season and the city experiences series of flash flood, putting the civic life at standstill for days at a stress. T...
Abrupt pressure fluctuations in a conduit due to sudden closure or opening of a valve can cause s... more Abrupt pressure fluctuations in a conduit due to sudden closure or opening of a valve can cause serious damage to the whole pipe network. This is a major concern of Hydraulic Engineers particularly, in case of hydropower plants—without the provision of Surge Tank. The pressure wave generated due to rapid pressure fluctuations, developed inside the pipe, is known as water hammer effect. Therefore, due to this water hammer effect, pressure as well as discharge through the pipe fluctuates. This phenomenon must be accounted for, while designing the conduit system to protect the network against catastrophic failure. Here, the governing equations of hydraulic pipe transients are discretized to obtain the Finite Difference Equation (FDE) through the Method of Characteristics (MOC). MATLAB is used as the operating tool to develop the numerical model, which is then validated with the available laboratory data. The numerical model is then applied for the butterfly valve and comparisons of pre...
The values of Manning‟s roughness coefficient “n” generally have been considered for any point in... more The values of Manning‟s roughness coefficient “n” generally have been considered for any point in channel bed as constant throughout the total time of prediction. But in real field the value of Manning‟s “n” varies not only depending on various factors such as channel irregularity, surface roughness, bed slope and vegetation cover but also it varies at the same point with effect of unsteadiness . In this study equations for unsteady resistance have been proposed using linear regression and spread sheet programming. Two unsteady resistance equations has been obtained here, one for high flood and another for moderate flood for a dam-break case in river Toce. The available data has been collected from the CADAM project (1999) and analysis has also been done in order to observe the variation of unsteadiness of water at various stations for both high flood and for moderate flood for the dam-break case.
International Journal of Modelling and Simulation, 2010
AbstractThis paper presents a numerical model to simulate the unsteady water and riverbed profile... more AbstractThis paper presents a numerical model to simulate the unsteady water and riverbed profile due to failure of a large dam in a natural river. The mathematical model is built upon the conservative laws of shallow water hydrodynamics. Over the recent decades, there have been continuing efforts to understand dam-break hydraulics and the majority of the studies have been carried out in laboratories where channel bed is assumed to be fixed under such a highly transient flow. Dam-break hydraulics of natural rivers is indeed complicated, and involves not only water flow, but also morphological changes in the riverbed, which in turn has modified the predicted flow profiles. Although very few numerical models are proposed for mobile beds, applications were only in simple laboratory channels. The present investigation carried out in a Himalayan river clearly shows that the free surface profiles and hydrographs are greatly modified by natural riverbed mobility under high supercritical dam-break flows, which is...
World Environmental and Water Resource Congress 2006, 2006
An investigation is carried out for numerical computations of dam break hydraulics in Natural Riv... more An investigation is carried out for numerical computations of dam break hydraulics in Natural Rivers with Explicit Finite Difference (EFD) Schemes. Although computational Dam Break Hydraulics is a topic of interest over more than 100 years, numerical simulations of dam break flow in relatively simple channels are found more often compared to real river flood simulations. Natural River channel with wide floodplains make the computation cumbersome as Natural River channels are highly non-prismatic with significant variations in River bed slope and friction. In this study, first order Diffusive Scheme, second order modified two-step Predictor Corrector scheme and Total Variations Diminishing (TVD) McCormack Predictor Corrector using Venn Leer Flux limiter are analyzed by solving unsteady flow equations in conservative and non conservative forms for simulating a hypothetical dam break situation in a Himalayan River in India . The height of the dam is 245 metres. Upstream length of the channel is 40,000 m and downstream is 64,000 m, the elevation of the bed of the channel changes from 545 m to 126.95 m, change in the channel width ranges from 300 m to 5650 m and Manning’s roughness coefficient varies from 0.03 to 0.035 depending on the channel characteristic. The numerical solutions of the EFD are relatively tested for their performances giving special emphasis to some parameters such as the flood depth at different sections and inundated area at different time periods after the failure of the dam and travel time of the flood waves; which are most important for the practicing engineers for efficient flood management. The computational aspects of the numerical models i.e. the implementation efforts of the schemes, run time required are compared. The applicability of the complex numerical corrections such as TVD in the numerical model for refinement in the solutions of dam break hydraulics in Natural Rivers is also examined. The stability and accuracy of the numerical solutions for both conservative and non conservative formulations are analyzed, and it is observed that numerical simulation of flows for complex real River topography in conservative forms with simple EFD schemes are advantageous from practical point of view compared to the higher order Explicit or Implicit Finite Difference or Finite Element schemes which increase the run time significantly and make the implementation complex.
Transients developed at the upstream, for abrupt closure of the downstream valve, is a concern to... more Transients developed at the upstream, for abrupt closure of the downstream valve, is a concern to be dealt with. It becomes more serious, if it is a high head hydro-electric power plant. At the load rejection, the developed tremendous high pressure can be catastrophic to the whole pipe network. Surge tank is installed to take care of the tremendous high pressure, so as to protect the whole system. The height of the surge tank is designed according to the highest possible water level during operation. The theoretical treatment of oscillations in a surge tank is not possible because of non-linearity of the governing equation. Numerical model is developed here, with MATLAB as the programming tool, to predict surge characteristics, validated with available data and applied to four – operating and on-going hydro-power plants in India and Pakistan, agreement achieved.
The problems of unsteady flow are frequently encountered in hydraulic power plant having a long c... more The problems of unsteady flow are frequently encountered in hydraulic power plant having a long conduit without the provision of surge tank due to sudden closing of the turbine valve. The velocity in water hammer situation fluctuates within the pipe from significantly high to an extremely low value with change in its direction after some interval of time. As a
Estimation of open channel bed roughness is a topic of continued interest. Many research works ha... more Estimation of open channel bed roughness is a topic of continued interest. Many research works have been done on open channel bed resistance. Depending upon the bed conditions of the open channel, Mannings' roughness coefficient, velocity of flow, depth of flow, Froude's number and other flow parameters varies. In this study the modeling of the effect of flow parameters on the estimation of bed roughness for various bed condition has been proposed. Key Words: Mannings' roughness coefficient , velocity of flow, depth of flow, Froude's number and bed roughness.
Leakage in the water distribution network at fault location incurring huge loss of scarce water r... more Leakage in the water distribution network at fault location incurring huge loss of scarce water resource is a serious point of concern. Assam is a flood-prone State, with heavy downpour in the catchment area of the mighty Brahmaputra. Guwahati, the capital of the State experience regular flash flood with incessant spells of heavy showers every year during rainy season. During no-flow timing, due to hydraulic gradient, pathogen and other contaminants may enter the submerged distribution network. Assam currently tops in the list of Infant Mortality Rate(IMR) in India, where water-borne disease considered to be a prime factor. Hence, under this study an effort has been made to develop models for locating the faults or leakage points in the water distribution networks for Greater Guwahati City. In this paper, Based on specific field study of 29 Piped Water Supply Schemes in and around Guwahati City, models have been developed with statistical linear regression method for location of fau...
The distribution of velocity in an open channel is not uniform due to the presence of free surfac... more The distribution of velocity in an open channel is not uniform due to the presence of free surface, the bed material of the channel, the discharge, the slope of the channel etc. A number of experiments have been done for three different bed materials with different discharges. The bed materials are the original bed material i.e. smooth iron bed, grass carpet and PVC. Velocity at different sections and different depths are taken with the help of pitot tube. From the experiment, it is found that the maximum velocity appears to occur at the free surface of the channel, and the average velocity for all the cases is coming almost 0.75 to 0.95 of the surface velocity.
Open channel flow resistance is a topic of continued interest. Many works have been done on the r... more Open channel flow resistance is a topic of continued interest. Many works have been done on the resistance of flow in open channel. The three co-efficients, namely Chezy’s co-efficient, Manning’s co-efficient and Darcy’s co-efficient are generally used in the calculation of flow resistance in open channel. In this paper an attempt has been made to study the various research works done to study the effect of different flow, channel and bed conditions on open channel flow resistance. The research works are done considering the three coefficients and also under different bed conditions.
Most of the rivers have cross sectional geometry of a compound section where a deep main channel ... more Most of the rivers have cross sectional geometry of a compound section where a deep main channel is bounded by shallow adjacent floodplains. Suitable estimation of discharge in compound channels is truly necessary for the design, operation and maintenance of the channels, utmost to prediction of flood. Generally compound channels have been analyzed by dividing the compound cross-section into relative sub-areas which are easier to analyze. In this paper the traditional one dimensional (1-D) method for estimating discharge capacity of straight compound channels are reviewed and applied to overbank flows in straight fixed compound channels. The predictive accuracy of these formulae was analysed by developing software using MATLAB with the help of experimental data obtained from the compound channel section of University of Birmingham. The accuracy of these methods to predict the total cross-section discharge is evaluated.
1M.Tech, student, Dept. of Civil engineering, ADTU, Guwahat, Assam , India 2Professor, Dept. of C... more 1M.Tech, student, Dept. of Civil engineering, ADTU, Guwahat, Assam , India 2Professor, Dept. of Civil engineering, ADTU, Guwahati, Assam , India ---------------------------------------------------------------------***--------------------------------------------------------------------Abstract – A compound channel consists of the main channel and flood plain. Bed resistance for main channel and flood plain are quite different. Here, proper prediction for flood in a compound channel the proper estimation of resistance is very important. Generally a composite resistance is estimated which depends on the resistance of the main channel and flood plain. Here, under this study the composite resistance predictions by different investigation have been compared with actual resistance value in case of a straight rectangular compound channel. Different investigated has found different formula for composite resistance. The percentage error for different resistance of composite formula has been c...
The water quality based on seasonal distribution pattern of physio-chemical characteristics of th... more The water quality based on seasonal distribution pattern of physio-chemical characteristics of the river Nambul flowing in heart of Imphal city were analysed during different years before and after onset of rain. The physio-chemical parameter of water such as water temperature, pH, Turbid ity, Dissolved Oxygen, BOD, Conductivity, Hardness, Alkalinity, COD, TDS, Chloride, Calcium and Magnesium were analysed. Water samples were collected from six sampling sites. Most of the parameters were not within the permissible value of drinking water. Turbidity was higher than normal limit and alkalin ity decreased through years. BOD and COD was much lesser in upstream than the downstream. The study suggest untreated domestic, disposal from market and household to the water body causes heavy pollution in river Nambul.
A compound channel is channel whose law is governed which mainly occurs in rainy season. In a Com... more A compound channel is channel whose law is governed which mainly occurs in rainy season. In a Compound channel with main channel and flood plains have been considered where exchange of momentum occurs, due to the presence of different vegetation in the bed channel, examples:rivers. In this paper all the research works has been reviewed with all the searched papers are of flows in compound channel. Such a review will help in enhancing the understanding for improving different conveyance and flow resistance in the field. Vegetation exists on the floodplains of almost all natural channels. Researchers have suggested equations for estimating composite roughness of an open channel flow which are good for simple channels and do not incorporate the interaction mechanisms that exist in a compound channel.
Leakage in distribution network accruing huge loss of coveted, depleting water resource has becom... more Leakage in distribution network accruing huge loss of coveted, depleting water resource has become a serious concern of water Engineers and planners. The National Rural Drinking Water Programme (NRDWP) guidelines of the Ministry of Drinking Water and Sanitation, Government of India, effective f rom April, 2009, stipulates 15% transmission loss, while the Min istry, by its communicat ion No F-11014/1/2015-Water-II-Part(5) dated 1st April, 2016, quotes media reports that 50% potable drinking water gets wasted because of leakages before it reaches the consumer and asked for, all the States to adopt suitable measures to check leakage in the condition of growing drinking water shortage, because of erratic monsoon and contaminated water in many region s. Guwahati, the second largest Metropolitan region in eastern India, next to Kolkata, gets heavy spells of rain during rainy season and the city experiences series of flash flood, putting the civic life at standstill for days at a stress. T...
Abrupt pressure fluctuations in a conduit due to sudden closure or opening of a valve can cause s... more Abrupt pressure fluctuations in a conduit due to sudden closure or opening of a valve can cause serious damage to the whole pipe network. This is a major concern of Hydraulic Engineers particularly, in case of hydropower plants—without the provision of Surge Tank. The pressure wave generated due to rapid pressure fluctuations, developed inside the pipe, is known as water hammer effect. Therefore, due to this water hammer effect, pressure as well as discharge through the pipe fluctuates. This phenomenon must be accounted for, while designing the conduit system to protect the network against catastrophic failure. Here, the governing equations of hydraulic pipe transients are discretized to obtain the Finite Difference Equation (FDE) through the Method of Characteristics (MOC). MATLAB is used as the operating tool to develop the numerical model, which is then validated with the available laboratory data. The numerical model is then applied for the butterfly valve and comparisons of pre...
The values of Manning‟s roughness coefficient “n” generally have been considered for any point in... more The values of Manning‟s roughness coefficient “n” generally have been considered for any point in channel bed as constant throughout the total time of prediction. But in real field the value of Manning‟s “n” varies not only depending on various factors such as channel irregularity, surface roughness, bed slope and vegetation cover but also it varies at the same point with effect of unsteadiness . In this study equations for unsteady resistance have been proposed using linear regression and spread sheet programming. Two unsteady resistance equations has been obtained here, one for high flood and another for moderate flood for a dam-break case in river Toce. The available data has been collected from the CADAM project (1999) and analysis has also been done in order to observe the variation of unsteadiness of water at various stations for both high flood and for moderate flood for the dam-break case.
International Journal of Modelling and Simulation, 2010
AbstractThis paper presents a numerical model to simulate the unsteady water and riverbed profile... more AbstractThis paper presents a numerical model to simulate the unsteady water and riverbed profile due to failure of a large dam in a natural river. The mathematical model is built upon the conservative laws of shallow water hydrodynamics. Over the recent decades, there have been continuing efforts to understand dam-break hydraulics and the majority of the studies have been carried out in laboratories where channel bed is assumed to be fixed under such a highly transient flow. Dam-break hydraulics of natural rivers is indeed complicated, and involves not only water flow, but also morphological changes in the riverbed, which in turn has modified the predicted flow profiles. Although very few numerical models are proposed for mobile beds, applications were only in simple laboratory channels. The present investigation carried out in a Himalayan river clearly shows that the free surface profiles and hydrographs are greatly modified by natural riverbed mobility under high supercritical dam-break flows, which is...
World Environmental and Water Resource Congress 2006, 2006
An investigation is carried out for numerical computations of dam break hydraulics in Natural Riv... more An investigation is carried out for numerical computations of dam break hydraulics in Natural Rivers with Explicit Finite Difference (EFD) Schemes. Although computational Dam Break Hydraulics is a topic of interest over more than 100 years, numerical simulations of dam break flow in relatively simple channels are found more often compared to real river flood simulations. Natural River channel with wide floodplains make the computation cumbersome as Natural River channels are highly non-prismatic with significant variations in River bed slope and friction. In this study, first order Diffusive Scheme, second order modified two-step Predictor Corrector scheme and Total Variations Diminishing (TVD) McCormack Predictor Corrector using Venn Leer Flux limiter are analyzed by solving unsteady flow equations in conservative and non conservative forms for simulating a hypothetical dam break situation in a Himalayan River in India . The height of the dam is 245 metres. Upstream length of the channel is 40,000 m and downstream is 64,000 m, the elevation of the bed of the channel changes from 545 m to 126.95 m, change in the channel width ranges from 300 m to 5650 m and Manning’s roughness coefficient varies from 0.03 to 0.035 depending on the channel characteristic. The numerical solutions of the EFD are relatively tested for their performances giving special emphasis to some parameters such as the flood depth at different sections and inundated area at different time periods after the failure of the dam and travel time of the flood waves; which are most important for the practicing engineers for efficient flood management. The computational aspects of the numerical models i.e. the implementation efforts of the schemes, run time required are compared. The applicability of the complex numerical corrections such as TVD in the numerical model for refinement in the solutions of dam break hydraulics in Natural Rivers is also examined. The stability and accuracy of the numerical solutions for both conservative and non conservative formulations are analyzed, and it is observed that numerical simulation of flows for complex real River topography in conservative forms with simple EFD schemes are advantageous from practical point of view compared to the higher order Explicit or Implicit Finite Difference or Finite Element schemes which increase the run time significantly and make the implementation complex.
Transients developed at the upstream, for abrupt closure of the downstream valve, is a concern to... more Transients developed at the upstream, for abrupt closure of the downstream valve, is a concern to be dealt with. It becomes more serious, if it is a high head hydro-electric power plant. At the load rejection, the developed tremendous high pressure can be catastrophic to the whole pipe network. Surge tank is installed to take care of the tremendous high pressure, so as to protect the whole system. The height of the surge tank is designed according to the highest possible water level during operation. The theoretical treatment of oscillations in a surge tank is not possible because of non-linearity of the governing equation. Numerical model is developed here, with MATLAB as the programming tool, to predict surge characteristics, validated with available data and applied to four – operating and on-going hydro-power plants in India and Pakistan, agreement achieved.
The problems of unsteady flow are frequently encountered in hydraulic power plant having a long c... more The problems of unsteady flow are frequently encountered in hydraulic power plant having a long conduit without the provision of surge tank due to sudden closing of the turbine valve. The velocity in water hammer situation fluctuates within the pipe from significantly high to an extremely low value with change in its direction after some interval of time. As a
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