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of West Bengal, India

Barman B.C.,River Research Institute | Sahu R.B.,Jadavpur University | Bhandari G.,Jadavpur University
ISH Journal of Hydraulic Engineering | Year: 2014

The backwater profile plays an important role in the design and performance of any hydraulic structures. Various methods are already in practice for the estimation of backwater profile. Present study attempts to estimate the backwater profiles due to barrage gate operations considering variable pond levels for alluvial channels using both theoretical analysis and laboratory model tests. The physical model tests were conducted for different pond levels and discharges. Backwater profiles obtained from theoretical and physical model tests data were compared with those obtained from available methods. Finally, a non-dimensional relationship has been established between the pond level and the backwater length. © 2014 Indian Society for Hydraulics. Source

Bardhan M.,River Research Institute
Water and Energy International | Year: 2011

This paper reports development of a relationship between friction factor of bed covered with ripples and the size and other geometric properties of these bed forms. The objective of the present study is to reveal the theory of resistance to flow. A relationship has been established between the ripple friction factor and the parameter modified relative roughness. An empirical relationship has also been developed for computation of mean velocity using experimental flume data. Source

Jana J.,Kalyani University | De Dalal S.S.,River Research Institute | Lahiri S.C.,Central Forensic Science Laboratory
Journal of the Indian Chemical Society | Year: 2011

The biogeochemical processes causing As-distribution in ground water of Bengal Delta Plain (BDP) areas are not well understood but As-mobilization in ground water are well known. Increased As-mobilization in ground water is due to increased manmade activities like mining, greater use of ammonium and particularly phosphates (as fertilizers, detergents, animal and plant wastes) and excess withdrawal of water causing depiction of water table. PO 4 3- and also NH 4 + ions with minerals may cause displacement of As V or As III from arsenic bearing minerals. However, processes leading to the increase in As-mobilization in ground water (even in surface waters of ponds etc.) are expected to increase with increase in P and N-budget in soils and water and with heavy withdrawal of ground water to meet the demands of increased industrialization and population. Intake of As-polluted water is the destiny for rural people where underground arsenic pollution is known unless proper remedial measure like use of filters for As-rcmoval from the polluted waters is undertaken. Most of the filters contain granular ferric hydroxides/activated alumina or aluminium silicate with or without metal oxides/ion-exchange resins. The working principles are the selective adsorption of AsO 3 3-/AsO 4 3-, oxidation of AsO 3 3- to AsO 4 3- by iron hjdroxides/oxides. The filtering capacity is dependent on pH but the capacity is affected by the presence of other ingredients like PO 4 3-, F -, Cl - ions etc. However, As-content in wells and As-removing ability of the Filters are not uniform. Some aspects of As-removing capability together with the effects of interfering ions are discussed. The high Fe content at pH > 7 causes precipitation of Fe as colloidal ferric hydroxide having better As-adsorption capability. This helps greater removal of As but is associated with clogging of filter beds having the opposite effect affecting the discharge of water. Frequent cleaning helps the restoration As-removal capability to a greater extent but shortens the life span and reduction of As-removal capability leading to ultimate breakdown of the filters at the vulnerable points. Suitable measures must be taken to reduce the gradual clogging and reduction of As-removal capability in designing the filters. Attempts should be made to find alternative methods for low cost As-removal process from ground water. Source

Rukshana F.,La Trobe University | Rukshana F.,River Research Institute | Butterly C.R.,La Trobe University | Xu J.-M.,Zhejiang University | And 2 more authors.
Journal of Soils and Sediments | Year: 2014

Purpose: This study aimed to investigate the effect of initial soil pH and organic anion-to-acid ratio on changes in soil pH. Materials and methods: Two soils (Podosol and Tenosol) along with two carboxylic acids (malic and citric acid) and their anions (sodium malate and citrate), commonly found in plant residues, were used in this study. Stock solutions of either malic acid and disodium malate or citric acid and trisodium citrate were added to pre-incubated soils at anion-to-acid ratios of 0:100, 10:90, 25:75, 50:50, 75:25, 90:10, 100:0 and at 0.25 g C kg-1 soil. Soils were adjusted to 80 % field capacity and mixed thoroughly, and three replicates of 50 g of each soil were transferred into individual plastic cores and incubated at 25 °C in the dark for 30 days. Soil pH, respiration, NH4 +, and NO3 - were determined. Results and discussion: Soil pH increased linearly with increasing organic anion-to-acid ratio. The addition of organic anions to soil resulted in net alkalinisation. However, the addition of organic acids immediately decreased soil pH. During subsequent incubation, soil pH increased when the organic anions were decomposed. Alkalinity generation was lower in the Podosol (initial pH 4.5) than in the Tenosol (initial pH 6.2), and was proportional to anion-to-acid ratio across all the treatments. Cumulative CO2-C release was approximately three times lower in the Podosol than the Tenosol at day 2 due to lower microbial activity in the low-pH Podosol. Conclusions: Increasing anion-to-acid ratio of organic compounds increased soil pH. Increases in soil pH were mainly attributed to direct chemical reactions and decomposition of organic anions. Low pH decreased the amount of alkalinity generated by addition of organic compounds due to incomplete decomposition of the added compounds. This study implies that organic anion-to-acid ratio in plant residues plays an important role in soil pH change. © 2013 Springer-Verlag Berlin Heidelberg. Source

Islam M.,St Xaviers College | Kar A.,River Research Institute | Kanoria M.,University of Calcutta
International Journal of Computational Methods in Engineering Science and Mechanics | Year: 2013

This paper deals with the thermoelastic interactions in a transversely isotropic, infinite hollow cylinder in which the boundaries are stress-free. There is no temperature in the inner boundary and heat flux is applied on the outer boundary. In the context of two-temperature generalized thermoelasticity theory, the three-phase-lag thermoelastic model and Green Naghdi model III (GN-III) are employed to study the thermophysical quantities. The Laplace transform is used to transform the coupled equations into the Laplace transformed domain. Then two different methods, the Galerkin finite element technique and eigen-value approach, are employed to solve the resulting equations in the transformed domain. The numerical inversion of the transform is carried out using Fourier-series expansion techniques. The physical quantities have been computed numerically and presented graphically in a number of figures. A comparison of the results for different theories (GN-III and three-phase-lag model) and for two different methods are presented. © 2013 Copyright Taylor and Francis Group, LLC. Source

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