Showing papers in "ISH Journal of Hydraulic Engineering in 2011"

Hec-ras based hydrodynamic model in prediction of stages of lower tapi river

Abstract: Hydrodynamic model of the lower Tapi river from Ukai dam to Surat city has been developed using well known unsteady open channel flow code HEC-RAS using field surveyed geometric data of the stream with appropriate upstream and downstream boundary conditions. The flood flows of years 1998, 2003 and 2006 have been simulated in the said model. The observed and simulated flood and stage hydrographs are compared at different stations on the river. The performance statistics reveal that simulated flood flows are in close agreement with observed flows. The model can be used for the flood forecasting in lower Tapi river downstream of Ukai dam.

Meshless point collocation method for 1d and 2d groundwater flow simulation

Abstract: For appropriate management of available groundwater, the flow behavior in the porous media has to be analyzed. Meshfree (MFree) method is an alternative numerical approach to commonly used Finite Difference Method (FDM) and Finite Element Method (FEM) to solve more complex engineering problems by simple and accurate manner. MFree method eliminates the drawback of meshing and remeshing as in FDM and FEM. Since there is no need to create a mesh, the time one would spend on conventional mesh generation can be saved. This can translate to substantial cost and time savings in modelling and simulation. In this paper, a meshless method called as Polynomial Point Collocation method (PPCM) with radial basis function has been developed for the groundwater flow simulation in porous media in one and two dimensions. The developed model has been applied for computing head distribution in a hypothetical confined aquifer having different boundary conditions and source, and sink terms. The developed model is test...

Flow through side square orifices in open channels

Abstract: A side orifice is a flow diversion structure which is widely used in irrigation works for diverting the flow from any main channel to its secondary channel. Analytical and experimental studies for flow through side square orifices in open channels are presented in this paper. Existing discharge equations for the side orifices are checked for their accuracy using the experimental data collected in the present study. The computed diverted discharges by the existing discharge equations were found to be inconsistent with the corresponding observed ones. Therefore, a new discharge equation is proposed in this study. The coefficient of discharge for the side orifice is dependent on the Froude number of the approach flow in the main channel and the ratio of width of the orifice to the width of the main channel. The computed discharges using the proposed equation were within ±5% of the observed ones.

A fuzzy based optimal irrigation planning for kakrapar right bank canal command area, gujarat, india

Abstract: The availability of water in space and time in the command area may be imprecise and unpredictable due to uncertainty in the inflows into the reservoir due to rainfall. The impreciseness and uncertainty can be tackled effectively with the fuzzy logics. In the present study, the multi-objective fuzzy linear programming (MOFLP) has been formulated for crop planning in the command area of Kakrapar right bank canal, under Ukai Irrigation Project, Gujarat, India. The objective of the study is to develop a Linear programming irrigation planning model and apply the same in MOFLP. The linear programming models have been developed for two objectives, net benefits and crop production with the set of constraints. The objectives have been formulated for optimal allocation of areas of different crops in the command area. The linear membership functions have been developed from the LP results and objectives were fuzzified over the tolerance range. The results of LP and MOFLP have been compared. Considering bot...

Characteristics of wave oscillations between two porous barriers

Abstract: The reflection and transmission characteristics of double porous barriers (DPB) have been studied through a numerical wave tank investigation. The numerical wave tank is modelled using a finite difference method based numerical scheme, BOUSS-2D. In the present study, the emphasis is given to the wave oscillations between the porous barriers (chamber) and its effect on the hydrodynamic performance. The wave oscillations measured inside the chamber were analysed qualitatively through phase portraits and quantitatively through spectral transformations. The analysis showed interesting features of the wave oscillations for different chamber to wavelength ratio, B/L. A sub-harmonic resonance is observed inside the chamber when B/L»0.2, which leads to reduction in the reflection coefficients, K for the DPB models. In addition, the effects of combination of porosity on the reflection and transmission characteristics of DPB are compared to that of a single porous barrier (SPB) of respective porosity. The ...

Experimental study of hydraulically efficient piano key weir configuration

Abstract: Piano Key Weirs are modified version of labyrinth weir with innovation to improve discharging capacity and more compatible for constructing on a existing or new spillway with lesser space requirement and structural stability. The objective of this study was to identify the Piano Key Weir in which the maximum discharge capacity at different UW with p (height of weir) could be achieved. To achieve this for different flow conditions, length magnification ratio (L/W) is taken from 3.56 to 7.40. Also, other parameters are taken in different combinations for getting optimum configuration of Piano Key Weir for better performance. With this in view, three phases of experimental campaign on eighteen Piano Key Weir models are reported in this paper. The ratio (r) of Piano Key Weir to linear weir discharge for a given head was seen to be more than one and found to increase with magnification ratio L/W upto a certain limit of h/p ratio. It was also found that performance of ratio of inlet and outlet cell wid...

Minimization of cost of cultivation using interactive decision making under fuzzy environment

Abstract: The uncertainties can be tackled by formulating the irrigation planning problem as Fuzzy Linear Programming (FLP). In the present study Single Objective Fuzzy Linear Programming (SOFLP) irrigation planning model is formulated for deriving the optimal cropping pattern plan with the objective of minimization of cost of cultivation for the case study of Jayakwadi Project Stage-I in Godavari river sub basin in the State of Maharashtra, India. The objective function coefficients, technological coefficients and stipulations/resources under consideration are taken as triangular fuzzy numbers. The interactive approach is used to solve SOFLP model by involving the Decision Maker in all phases of decision making process. The SOFLP model gives better result at highest degree of the membership value by keeping balance between feasibility degree of constraints and satisfaction degree of objective.

Application of the 1d-quasi 2d model tinflood for floodplain inundation prediction of the river thames

Abstract: TINFLOOD, a simplified numerical model developed for simulation of floodplain inundation, is applied to predict the extent of flooding at a small reach of the River Thames, UK. River flow is computed by solving the de Saint Venant equations with a one-dimensional finite volume approach. Over-bank flood water spillage from the river onto the floodplains is computed considering mass exchange only between the one-dimensional river cells and the adjacent floodplain cells. Flow exchange between the river and floodplain cells or that between adjoining floodplain cells is represented by a weir type equation. The model employs a linearized form of the flow equation for avoiding instability, common to such coupled models. The rigorously tested model is applied in this study for predicting the extent of inundation for a flood event to a stretch of the River Thames, United Kingdom and compared with the corresponding observed imagery of the flood extents.

Impact of climate and land use changes on the flood characteristics of the brahmaputra basin

Abstract: A macro-scale distributed hydrological model (DHM) has been used to assess the possible future changes in the flood characteristics of the Brahmaputra basin, India. Future projected meteorological scenario from a regional climate model (RCM) simulation and the ‘Best Guess’ land use change scenarios were used to obtain the spatio-temporal changes in flood generation and its propagation through the Brahmaputra river and its tributaries. This study reveals that the projected climate change would affect the flood characteristics more significantly than the land use/land cover changes. Alteration of paddy agriculture fields would significantly change the flood characteristics in the valley. Hydrological impacts of changing land use/land cover have been found to be more dominating in the drier years compared to the wet years.

Reactive transport through porous media using finite-difference and finite-volume methods

Abstract: In this paper, finite-volume method (FVM) and implicit finite-difference method (FDM) have been used to solve multiprocess nonequilibrium (MPNE) transport equation for reactive solute transport through porous media. A review of the literature reveals that the performance of the MPNE transport model for advection- and dispersion-dominant cases has not been analysed. The main objective of the present study is to asses the performance of both FDM and FVM in the presence of high value of Peclet number (Pe) for reactive transport through porous media. It has been shown that in case of advection-dominant transport (i.e. at high values of Pe), the FDM numerical model remains stable and oscillation free, when the values of mass transfer and sorption rate coefficient are high. Further, the FVM model is capable of simulating advection-dominant transport irrespective of the values of mass transfer and sorption rate coefficient. This is established through simulation of the experimental data of Strontium.

Seasonal and medium term changes in the shoreline position at selected stations on malabar coast, kerala

Abstract: Coastal environment data pertaining to wave parameters, wind, littoral current, beach characteristics and shoreline position are being collected from the selected stations on the Kerala coast since 1973. To assess the changes during different seasons and years, shoreline positions at different points are measured regularly with respect to the reference point. Analysis of shoreline position from stations located on Malabar (northern Kerala) coast revealed that the fluctuation is maximum during south-west monsoon followed by non-monsoon season. Different stations show different pattern of shoreline changes like fluctuation, erosion, stable and accretion. The maximum changes in the shoreline position (erosion) happened at Kozhikode whereas at Padinjare Vemballur, the changes are the minimum (accretion).

Stochastic modelling of groundwater contamination around an ash slurry holding dyke

Abstract: The present study comprises an application of a deterministic two-dimensional horizontal contaminant transport model to a contaminant transport problem treating transmissivity as a stochastic field. The problem concerns with disposal of ash slurry emanating from a thermal power plant on the upstream of a dyke. The head of the slurry causes entry, and subsequent lateral movement of the slurry into the groundwater system. The stochasticity is accounted for by Monte Carlo simulation that essentially involves generating several realizations of the transmissivity field, and computing corresponding realizations of the selected random state variable viz. contaminated areas at advancing times. The realizations are processed to arrive at the corresponding probability distribution functions. Finally, factor of safety in respect of the permissible limit on the contaminated area is correlated to the acceptable level of risk.

Analytical solutions for alternate depths

Abstract: Triangular, parabolic rectangular and trapezoidal sections are practical open channel sections. For rectangular channel section it is possible to express the alternate depths analytically. For other sections the alternate depths are presently obtained by trial and error procedure. In this paper exact analytical solutions of alternate depths for exponential and trapezoidal open channel sections have been obtained in the form of fast converging infinite series and algebraic equations.

Stability of wide toe berm breakwater with varying seabed slope

Abstract: Stability of rubblemound breakwater as a whole depends primarily upon the stability of the individual armour units against the wave attack. The manner in which waves interact with the structure is governed not only by the form of the structure, but also by the seabed slope. In order to study the effect of seabed slope on the stability, hydraulic model tests were conducted on a breakwater section in a wave flume with different seabed slopes of 1: 120 and 1: 50. The tests were conducted with breaking and non-breaking waves with two different water levels and two wave periods. Model studies indicated that the stability of armour units decreases with steeper bed slopes. The results are useful for optimising the design of breakwaters. Simulation of seabed slope in the hydraulic model is crucial in finalising the design of rubblemound breakwater section.

Concrete cubes as armour unit—an experimental study for berm breakwater

Abstract: Berm breakwater consists of a wide berm at or around the water level and has an armour layer, whose shape changes in response to wave action yielding a stable profile In the present study the influence of wave height, wave period and berm width on the stability of the breakwater as well as on the wave runup and wave rundown are studied Experiments were conducted on berm breakwater model of 1:30 scale using concrete cubes as armour units For the given experimental conditions the stability number was found to vary from 221 to 363 Further the model in 037m water depth was more stable than the one in 040 and 043m The runup values were within the range of 052 to 108 While, the rundown values had the variation from 045 to 088

Grip length for bridge piers

Abstract: Proper estimation of grip length (foundation depth of pier below maximum scour level) is very important for safety of bridge piers, Lacey's recommendations are used for the design of grip length for bridges in India. Validity of Lacey's recommendation has been investigated by both experimental and analytical approaches. Experiments are conducted to find the stability of pier for three shapes of piers and for two types of median size sediments. Experiments indicate minimum value of grip length <0.2(h+hs), where (h+hs) indicates depth measured below free surface up to maximum scour level. Stability analysis of forces acting on caisson pier for three different cases is carried out. Lacey's recommendation for railway bridge design is in stable zone for the cases considered. However, the Lacey's recommendation for road bridge pier is in stable zone for few cases and for remaining they are in unstable zone. Effect of earthquake forces on stability of caisson piers are not considered in this analysis.

Rolling motion of particles over transitionally-rough bed

Abstract: The rolling motion of sediment particles and the near bed (wall region) turbulence of a transitionally-rough bed surface are studied experimentally using an acoustic Doppler velocimeter and a real time high speed imaging system. Path traced by the sediment particles and the corresponding velocity components were obtained from the high speed images captured using digital image processing technique. Sediments of different sizes were tested. The near bed turbulence characteristics were quantified by measuring the instantaneous velocity components and then retrieving the time averaged velocity components, turbulence intensity components and turbulence stresses. The competence of the two dimensionless parameters provided by Sekine and Kikkawa (1992) for saltation is tested with the results obtained on the rolling motion of the sediment particles over transitionally-rough beds.

Kirpich and williams times of concentration in musle: a case study

Abstract: Water is one of the most vital requirements for sustenance of life. Water, along with soil, forms the combination of the most essential natural resource for economic and social development. A study of soil and water dynamics at a watershed level can facilitate a scientific approach to a conservation and management plan for them. The present study is an attempt to implement Modified Universal Soil Loss Equation (MUSLE) using Soil Conservation Service Curve Number (SCS-CN) method for runoff estimation and comparison of soil loss results for the catchments of Baindur Hole and Yedamavina Hole in Udupi district of Karnataka state obtained by times of concentration calculated by the Kirpich equation and the Williams equation. Preparation of base map and thematic maps was carried out using IRS-1C, LISS-III image for LU/LC and from SOI toposheet in a GIS environment for overlaying and extraction of results. The time of concentration estimated by the Kirpich formula is lower in all cases; hence the corres...

Technical feasibility analysis of submarine pipelines for intake of sea water with high total suspended sediment loads

Abstract: Submarine pipeline is used as a seawater intake system since it is cost effective compared to canal and jetty type intake structures. Open channel type intakes attract large deposition of sediments and hence periodic maintenance dredging is essential. Jetty type seawater intake is generally expensive. Much coastal water around the world hold high concentration of Total Suspended Sediments (TSS) like the coastal waters of Sabiya area, Kuwait in the north western part of Arabian Gulf. The existing seawater intake channel of a power plant is attracting significant settlement of TSS. Maintenance dredging of about 400,000 m25/year is carried out. It is proposed to increase the seawater intake for a proposed 2050 MW additional power plant and hence further increase in the TSS settlement is anticipated, if the present sea water intake system is used. Alternative type of seawater intake system, which can reduce the TSS is explored. Feasibility study is carried out to reduce the sediment entry into the po...

Physical model studies on stability of concrete armoured breakwaters

Abstract: As the breakwater construction started moving in to deeper waters, the wave load on its armour increased resulting in usage of heavier armour units inviting environmental and logistical problems. With the advancement in the technology, concrete armour units have been extensively replacing the natural stones with benefits such as saving in the material and cost while reducing loads on the seabed and helping in construction of environment etc. Tandem breakwater and berm breakwater could be the alternative solutions for the above said case. This paper presents the two cases of physical model studies on the stability of concrete armoured structures, one with tandem breakwater and another on berm breakwater. Both the models are subjected to monochromatic waves with varying characteristics. From the study it was observed that in case of tandem breakwater the crest width of submerged reef and the distance between breakwater and reef are the defining parameter while in case of berm breakwater the height ...

Wavelet-ann model for diffuse pollution prediction in streams

Abstract: The use of herbicides, pesticides, and other chemicals in agricultural fields increases the concentration of chemicals in streams which severely affects the health of human and environment The transport of chemical pollutants into river or streams is not straight forward but complex function of applied chemicals and land use patterns in a given river or stream basin which are difficult to quantify accurately Development of models based on temporal observations may improve understanding the underlying the hydrological processes in such complex transports Recently, artificial neural network (ANN) as a non-linear inter-extrapolator is extensively used by hydrologists Present work utilized temporal patterns extracted from temporal observations using wavelet theory These patterns are then utilized by an artificial neural network (ANN) The wavelet-ANN conjunction model is then utilized to predict the monthly concentration of diffuse pollution in a stream The application of the proposed methodolo

Practical singular open-channel sections

Abstract: For a given discharge and channel geometry critical flow and uniform flow occur at unique depths known as the critical, and the normal depths, respectively. For some sections the governing equations for these depths (critical flow equation and resistance equation, respectively), are satisfied for all the depths. As the governing equations do not yield a unique solution, these sections are singular. Reported herein are the equations of the singular section shapes for critical and uniform flows. It will be interesting to observe flow phenomenon in this channel, as it does not sustain gradually varied flow.

Hybrid mathematical model for surge analysis: a case study

Abstract: Over the past few decades mathematical modeling technique is in vogue. A large number of water hammer cases have been analyzed using this technique, not only for simple systems but also for those with rather complex situations. The present analysis for a water conductor system having intermediate boundary condition such as pump behavior needed a hybrid mathematical model. The results of analyzing such system and comparing them with those obtained from the hydraulic scale model give more confidence in adoption of the mathematical technique.

Electrical resistivity survey on the left branch canal of high embankment of tungabhadra dam, miles 69, 77 & 85, karnataka state

Abstract: In order to investigate the presence of concealed cavities (locally known as Bongas), responsible for the seepage in the high embankments at miles 69,77 and 85 of left branch canal, Tungabhadra project, Karnataka State, Electrical Resistivity Profiling (ERP) and Imaging (ERI) were used. ERP was carried out in canal dry condition and both ERP and ERI were deployed at different locations (after due interpretation of the ERP studies) in canal filling condition. The geophysical investigations are carried out in April 2007 (canal dry condition) and November 2007 (canal filling condition). ERP was carried out using Schlumberger configuration with half electrode spacing (AB/2) of 10.0 m 15.0 m and 20.0 m. The ERI was carried out with Wenner & Schlumberger arrays with an inter-electrode spacing of 5.0 m. The locations, where relatively low resistivity values were observed during the canal empty condition and still lower values in canal filling conditions were attributed to the cavities. Thus the cavities...

Hydraulic investigations for post tsunami impact at hut bay—a case study

Abstract: Hut Bay is situated in the Little Andaman between Andaman and Nicobar Islands and is about 110 km towards south of Port Blair. Hut Bay has a minor port which caters to the inter island vessels. The devastating earthquake and tsunami of 26th December, 2004 has caused severe damage to the rubble mound breakwater at Hut Bay and adjoining areas. Hydraulic investigations were carried out at CWPRS, Pune to assess the impact of the tsunami in the vicinity of Hut Bay Port to facilitate restoration of the damaged breakwater and for the future development. Numerical models MIKE-21 HD and MIKE-21 ST were used to simulate hydrodynamics and siltation respectively, in order to assess the post tsunami impact on the flow and siltation aspects in the bay. The environmental data used for the present study includes waves, wind, tide, currents and sediment characteristics. The studies elucidated that there is no significant change in the flow field and siltation pattern/bed thickness after the devastating tsunami. B...

Studies for improvement of flow conditions at proposed barrage across river falgu

Abstract: The Falgu River flows in northward direction almost parallel to and on the West of Gaya. To full fill the irrigation demands in the lower basin of river Falgu, Government of Bihar, has proposed a barrage on river Falgu at Uderasthan. Model studies for the proposed barrage has been entrusted to CWPRS to decide location, orientation, alignment, waterway of barrage, afflux, design of river training works such as guide bunds. The model studies indicated that the proposed water way of 300m would be adequate. Suitable guide buds were recommended on both sides of the barrage to improve the flow conditions and distribute the flow more uniformly at the barrage axis. Measurement of water level, velocity, angle of flow and discharge intensity along the proposed barrage axis indicated no undesirable flow conditions at the proposed barrage axis. The alignment of proposed barrage axis at about 200 m upstream of Uderasthan weir is hydraulically found satisfactory and hence recommended.