Faculty Publications
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Item Biological sulfide oxidation using autotrophic Thiobacillus sp.: Evaluation of different immobilization methods and bioreactors(2009) Ravichandra, P.; Gopal, M.; Jetty, A.Aims: Evaluation of various immobilization methods and bioreactors for sulfide oxidation using Thiobacillus sp. was studied. Methods and Results: Ca-alginate, K-carrageenan and agar gel matrices (entrapment) and polyurethane foam and granular activated carbon (adsorption) efficacy was tested for the sulfide oxidation and biomass leakage using immobilized Thiobacillus sp. Maximum sulfide oxidation of 96% was achieved with alginate matrix followed by K-carrageenan (88%). Different parameters viz. alginate concentration (1%, 2%, 3%, 4% and 5%), CaCl2 concentration (1%, 2%, 3%, 4% and 5%), bead diameter (1, 2, 3, 4 and 5 mm), and curing time (1, 3, 6, 12 and 18 h) were studied for optimal immobilization conditions. Repeated batch experiments were carried out to test reusability of Ca-alginate immobilized beads for sulfide oxidation in stirred tank reactor and fluidized bed reactor (FBR) at different sulfide concentrations. Conclusions: The results proved to be promising for sulfide oxidation using Ca-alginate gel matrix immobilized Thiobacillus sp. for better sulfide oxidation with less biomass leakage. Significance and Impact of the Study: Biological sulfide oxidation is gaining more importance because of its simple operation. Present investigations will help in successful design and operation of pilot and industrial level FBR for sulfide oxidation. © 2009 The Society for Applied Microbiology.Item Solid suspension and liquid phase mixing in solid-liquid stirred tanks(2009) Sardeshpande, M.V.; Sagi, A.R.; Juvekar, V.A.; Ranade, V.V.Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so on. In designing and optimizing such processes, suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses on identifying critical impeller speed for just suspension of solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in solid-liquid suspensions were also studied. A new way of characterizing solid-liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications for designing solid-liquid stirred tanks. © 2009 American Chemical Society.Item Experimental Studies on Behaviour of Stone Columns in Layered Soils(2011) Shivashankar, R.; Dheerendra Babu, M.R.D.; Nayak, S.; Rajathkumar, V.Stone columns are found to be effective and economical ground improvement technique in soft grounds. Understanding its behaviour when they are installed in stratified soils, in particular when the upper layer consists of weak soil, will be of great practical significance. This paper presents results from a series of laboratory plate load tests carried out in unit cell tanks to investigate the behaviour of stone columns in layered soils, consisting of weak soft clay overlying a relatively stronger silty soil, for various thicknesses of the top layer. Tests were carried out with two types of loading (1) the entire area in the unit cell tank loaded, to estimate the stiffness of improved ground and (2) only the stone column loaded, to estimate the limiting axial capacity. Laboratory tests were carried out on a column of 90 mm diameter surrounded by layered soil, for an area ratio of 15%. It is found that the depth of top weak layer thickness has a significant influence on the stiffness, load bearing capacity and bulging behavior of stone columns. © 2011 Springer Science+Business Media B.V.Item Land use scenario analysis and prediction of runoff using SCS-CN method: A case study from the Gudgudi tank, Haveri district, Karnataka, India(2011) Bhagwat, N.B.; Shetty, A.; Hegde, V.S.Runoff from the Gudgudi tank catchment (209 ha) near Hangal in the Northern Karnataka is estimated employing Soil Conservation Services(SCS) model based on the hydrological data and land use/ land cover data. Rainfall measured for 2006 using a tipping bucket indicated annual rainfall of 887.7mm in the tank catchment. Textural characteristics of the soil indicate sandy-clayey type which corresponds to hydrological soil group "C and D". Average Soil infiltration rate of 0.18 cm/hour for the forest-land and 0.21 cm/hour for agriculture land has been observed. Weighted curve number is arrived based on the antecedent moisture conditions, and runoff is estimated for the existing land-use. Areastorage curve is constructed using the tank bed contours. Considering the hypothetical changes in the agriculture and forest area coverage, optimum conditions for maximizing the runoff and storage in the tank is arrived. The analysis suggests land use pattern of 15% of forest cover and 85% of agriculture land coverage in this region provide maximum runoff and storage in the tank for sustainable development. © 2011 CAFET-INNOVA TECHNICAL SOCIETY.Item Performance of granular columns in dispersive soils(Thomas Telford Services Ltd ttjournals@ice.org.uk, 2014) Nayak, S.; Dheerendra Babu, M.R.; Shivashankar, R.; James, N.The soils found abundantly along the Konkan belt in peninsular India are lateritic soils and lithomargic clays. The locally available lithomargic clayey soils are problematic in the sense that their strength reduces drastically under saturation conditions, which is typical behaviour of the dispersive type of soil. Most foundations are placed on this soil layer. This paper presents results from a series of laboratory plate load tests carried out in unit cell tanks to investigate the behavior of granular columns in these weak (lithomargic clay) grounds. Tests are carried out with two types of loading: with the entire area in the unit cell tank loaded, to estimate the stiffness of the improved ground; and with only the granular column area loaded, to estimate its limiting axial capacity. Investigations were carried out by varying the area ratio (or spacing), diameter of granular columns, end condition and column configuration. The load-settlement behaviour, stiffness and bulging behaviour of granular columns are analyzed. It is found that the ground treated with granular columns exhibits a high load-carrying capacity and stiffness, and a significant reduction in settlement, compared with the untreated ground. © Ice publishing: All rights reserved.Item Experimental and finite element analysis of power transformer(Structural Engineering Research Centre, 2014) Nandam, N.; Ramesh Babu, R.R.; Venkataramana, K.Post earthquake studies have clearly shown that the seismic performance of substation is very weak and results in damage causing huge direct and indirect loss to the power utilities. Considerable time is spent to repair, retrofit or replace the damaged substation equipment and to restore power supply. Many substation equipments failed when installed in the substation due to moderate earthquake forces though these equipment were experimentally qualified. Power transformer is one of such critical equipment of substation. Vibrations due to earthquake amplified by the transformer tank causes failure in the porcelain bushings mounted on the top of the transformer tank. An attempt has been made in this study to identify resonance frequencies and corresponding damping ratios of a typical transformer by both experimental and numerical methods. In addition, ground acceleration amplification is also calculated from shake table experiments and response analysis of finite element model.Item Noniterative Method for Combined Acoustic-Electrical Partial Discharge Source Localization(Institute of Electrical and Electronics Engineers Inc., 2018) Antony, D.; Punekar, G.S.The combined acoustic-electrical system is used in the factory or plant environment for the partial discharge (PD) source localization in power transformers. A noniterative method for this combined acoustic-electrical PD-locator-system is devised and presented in this paper for the first time. It employs three acoustic emission (AE) sensors. The proposed method is compared with the existing noniterative method used in the all-acoustic system, which employs four AE sensors. The comparative study shows that the proposed method can locate the PD source irrespective of its position within the tank, whereas the prevailing noniterative method for the all-acoustic system fails to locate the PD source at certain positions within the tank. The effect of the sensor positioning on the performance of the method is studied, and some guidelines for the sensor placement on the transformers tank wall in a factory or plant environment are suggested. The proposed method is also applied to the data taken from the published literature. The localization results are compared with those of an existing iterative method (Newton's method) to prove its superiority in terms of computational time. © 1986-2012 IEEE.Item Application of remote sensing and GIS for identification of potential ground water recharge sites in Semi-arid regions of Hard-rock terrain, in north Karnataka, South India(Springer Science and Business Media Deutschland GmbH, 2018) Bhagwat, T.N.; Hegde, V.S.; Shetty, A.Hydro-geomorphological characteristics, together with soil, slope, lineament density and Land use Land cover are signatures of potential ground water recharge areas, and are vital for water harvesting. In the present paper, Fifth order sub-basins in Semi-arid regions of the Varada River basin in South India is studied for selection of suitable area for recharge and prioritize the sub-basins using Indian Remote Sensing satellite (IRS) P6; Linear Imaging Self Scanning Sensor (LISS III) and ArcGIS 9.2. The Fifth order sub-basins of the Varada River spread in Hard-rock terrain and of different agro-climatic zones. The study shows that there are significant spatial variations in the fifth order basins with respect to their morphometric characteristics such as the basin area, drainage density, bifurcation ratio, and circularity ratio, constant of channel maintenance and slope of the basin. These variations reflect the differences in the hydrological process in the different Sub-basins. Based on the variations in the linear, aerial, relief as well as the slope, lineament density, and precipitation pattern rankings are assigned for each parameter with respect to ground water recharge within the Subbasins. Weighted sum overlay for precipitation, Land use, soil and Water table fluctuation are used to select the suitable areas of recharge within the sub-basins. Buffers created for lineaments and drainage networks were intersected with the suitable area of recharge for the probable tank's locations for recharge. The tank locations identified after intersection and having higher stream orders are further filtered for the identification of potential sites for ground water recharge. In the prioritized sub-basins SB-8, SB-10, SB-11 locations have been selected for recharge. © 2018, Springer International Publishing AG, part of Springer Nature.Item Sloshing dynamics and performance of porous baffle arrangements in a barge carrying liquid tank(Elsevier Ltd, 2019) Nasar, T.; Sannasiraj, S.A.An experimental investigation is conducted to explore the effectiveness of porous baffles placed at l/3 and 2l/3 in the sloshing tank. A tank aspect ratio, hs/l of 0.488 which corresponds to 75% filled condition is considered. The sloshing tank is kept inside the freely floating barge and subjected to regular beam sea waves. A wave height of 0.1 m and excitation frequencies ranging from 0.45 Hz to 1.54 Hz is adopted. Baffles with three different porosities of 15%, 20.2% and 25.2% are used. The effectiveness of baffles placed at l/3 and 2l/3 is explored on comparison with the performance of single porous baffle kept at l/2 and a solid submerged baffle place at l/2. Sloshing dynamics for the baffles placed at l/3 and 2l/3 and barge responses are also discussed. © 2019 Elsevier LtdItem Performance assessment of porous baffle on liquid sloshing dynamics in a barge carrying liquid tank(Taylor and Francis Ltd., 2021) Nasar, T.; Sannasiraj, S.A.; Sundar, V.A comprehensive experimental work is done to investigate sloshing dynamics in a partially liquid-filled baffled tank, equipped with a floating barge. An aspect ratio(hs /l, liquid depth, hs to length of tank, l) of 0.488 (above critical fill level), which corresponds to 75% fill level, is considered. The barge was subjected to regular wave excitations with a wave height of 0.1 m and frequencies ranging from 0.45Hz to 1.54Hz under beam sea condition. In addition, porous baffles are placed inside a rectangular tank to study its effectiveness in reducing the sloshing energy. Three different porosities of 15%, 20.2% and 25.2% at l/2 are considered. The effectiveness of baffles is explored and the salient results for a single porous baffle are discussed. It is learnt that the effect of baffles on sway and roll responses is significant, whereas it is insignificant on heave. Porous baffles are effective in suppressing the sloshing oscillation in the vicinity or at wave excitation, fw =f 1, whereas the sloshing is amplified at fw =f 2 and fw =f 3 due to the resonance condition of modified natural frequencies. © 2020 Informa UK Limited, trading as Taylor & Francis Group.