Faculty Publications
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Item Monitoring Spatial and Temporal Scales of Shoreline Changes in the Cuddalore Region, India(Elsevier, 2018) Subbarayan, S.; Kulithalai Shiyam Sundar, K.S.S.; Vishnuprasath, S.R.Coastal zones are constantly undergoing changes in shape and environment due to natural processes and anthropogenic interventions. The study of shoreline change has become a matter of great concern in recent years. The measurement of shorelines is a key factor in coastal zone construction. A shoreline change study was carried out for a 33-km stretch of the Cuddalore coast between Gadilam and the Vellar River. Satellite images (2000, 2005, 2010, and 2015) were taken as an input dataset in a GIS platform. Automatic shoreline delineation was attempted by a masking technique using ENVI software. In this study, the modification of normalized difference water index (MNDWI) method extracted the raster shoreline-based contrast value of coastal pixels and thresholding techniques for segmenting water and land regions. DSAS software and reference digitized shoreline boundary data were used for the analysis of shoreline changes. End point rate (EPR) and net shoreline movement determination showed the northern part of the Uppanar River mouth under erosion (region A to C and E) and sediment deposition at an accretion rate of 7.6. m/year from EPR and 114. m from NSM. The maximum shoreline erosion rate was -. 3.8. m/year from EPR and -. 57. m from NSM. From these attempts and results, a methodical approach for detection and monitoring of shoreline changes on spatial and temporal scales of interest have been suggested. © 2019 Elsevier Inc. All rights reserved.Item Slope stability studies of excavated slopes in lateritic formations(Springer, 2019) Shivashankar, R.; Thomas, B.C.; Krishnanunni, K.T.; Venkat Reddy, D.V.The study area for this paper is coastal Karnataka in India, which has laterites and lateritic soils. The soil stratification in this area mainly consists of lithomargic clay, which is a product of laterization, sandwiched between the hard and porous weathered laterite crust at the top and the hard granite or granitic gneiss underneath. This lithomargic clay, locally called as ‘shedi soil’ behaves as dispersive soil and is also highly erosive. In the first stage of this study, laboratory erosion studies are conducted by using the hole erosion test apparatus on controlled shedi soil samples. Erosion observed in the HET is accelerated due to slaking irrespective of dispersive nature of the soil. Erosion problems were also dealt with using a stabilizer, calcium lignosulfonate and resulted in high increase in its erosion resistance. In the second stage of this study, slope stability studies of excavated slopes in lateritic formations are conducted considering intensity of rainfall, ponding and seepage, apart from the usual geotechnical parameters. The slopes steeper than 60° are not stable in the case of shedi soil considered here. © Springer Nature Singapore Pte Ltd 2019.Item Monitoring Spatial and Temporal Scales of Shoreline Changes in the Cuddalore Region, India(Elsevier, 2019) Subbarayan, S.; Kulithalai Shiyam Sundar, K.S.S.; Vishnuprasath, S.R.Coastal zones are constantly undergoing changes in shape and environment due to natural processes and anthropogenic interventions. The study of shoreline change has become a matter of great concern in recent years. The measurement of shorelines is a key factor in coastal zone construction. A shoreline change study was carried out for a 33-km stretch of the Cuddalore coast between Gadilam and the Vellar River. Satellite images (2000, 2005, 2010, and 2015) were taken as an input dataset in a GIS platform. Automatic shoreline delineation was attempted by a masking technique using ENVI software. In this study, the modification of normalized difference water index (MNDWI) method extracted the raster shoreline-based contrast value of coastal pixels and thresholding techniques for segmenting water and land regions. DSAS software and reference digitized shoreline boundary data were used for the analysis of shoreline changes. End point rate (EPR) and net shoreline movement determination showed the northern part of the Uppanar River mouth under erosion (region A to C and E) and sediment deposition at an accretion rate of 7.6m/year from EPR and 114m from NSM. The maximum shoreline erosion rate was −3.8m/year from EPR and −57m from NSM. From these attempts and results, a methodical approach for detection and monitoring of shoreline changes on spatial and temporal scales of interest have been suggested. © 2019 Elsevier Inc. All rights reserved.Item Failures Investigation of Marine Propellers in Corrosive Environments(Springer Nature, 2021) Mirashi, V.U.; Johnson, S.; Hegde, S.; Vijayan, V.; Cadambi, S.Marine corrosion failure of fishing boat propellers made of cast Nickel Aluminium Bronze were investigated. Specimens extracted from the corroded propellers were characterized by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The alloy comprises several Fe3Al (κ1, κ2, κ4), NiAl (κ3) type intermetallic precipitates and β’ martensite embedded in Cu-rich α-matrix. Transverse sections of the corroded region showed two distinct zones; a non-uniform top oxide layer and a partially corroded zone with selective corrosion of the β’ martensite which run parallel to the κ3 precipitates. From the microstructural analysis it is adjudged that the aggressive local corrosion of the matrix is preceded by cracking of the oxide by erosion, cavitation, etc., A slow growth of the oxide layer follows that reduces the corrosion rate. However, the corrosion cycle repeats on erosion or cracking of the oxide layer when the propeller is used in marine waters. Coupon specimens immersed in actual marine conditions is presented that supports the above theory. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item The influence of microwave sintering on the tribological performance of powder metallurgy based aluminum cenospheres composites(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Ananda Kumar, M.G.; Seetharamu, S.; Sampath Kumaran, P.; Nayak, J.The Metal Matrix Composites (MMCs) especially Aluminum based systems have unique advantages of having superior mechanical, chemical and electrical properties, in addition to light weight and high stiffness. In this work, composites comprising of Aluminum with varied concentrations of Cenospheres as reinforcement was produced by Powder Metallurgy (PM) route. The densification of the composites was effected both by conventional and Microwave (MW) sintering techniques. The microstructures of the sintered samples were observed through scanning electron microscope (SEM) and phases by x ray diffraction technique (XRD), followed by evaluation of tribological parameter namely slide wear behavior and solid particle erosion resistance. The densities and the Brinell hardness values for the samples were also evaluated. The results showed that microwave sintered samples exhibited higher hardness, lower erosion and slide wear loss. © (2015) Trans Tech Publications, Switzerland.Item Studies on the role of HVOF coatings to combat erosion in turbine alloys(Elsevier Ltd, 2018) Prasanna, N.D.; Siddaraju, C.; Shetty, G.; Ramesh, M.R.; Reddy, M.Erosive wear is caused by the action of sliding or impact of solids, liquids, gases or the combination of these. Solid particle erosion is an important material degradation mechanism encountered in a number of engineering systems such as gas turbine engines, thermal power plants, coal slurry pipe lines. Erosive action results from the impact of particulates, such as coal ash, dolomite and un-burnt carbon particles on the surface of turbine. Super alloys developed for high temperature applications suffer from the drawback that the strength and the erosion-corrosion resistance at high temperature exhibited are poor. To improve the resistance property, one way would be the use of coatings on the super alloy component. Coatings take care of the problems related to erosion whereas the super alloys take care of the requirement of strength at elevated temperature. Various coatings have been highly attractive; however, High Velocity Oxy-fuel (HVOF) process, a family of thermal spray techniques uses kinetic energy of the burnt gases to soften and to propel the spray powder producing dense very low porosity, good inter-particle cohesion and well bonded coatings. In the present study successful attempts have been made to spray Stellite-6, 10%Al2O3+90%CoCrAlTaY and 25%Cr3C2-20(Ni-Cr)+75%NiCrAlY on three kinds of turbine alloys, namely Ti-6Al-4V, Co-based super alloy (Super co 605) and Fe-based special steel (MDN121).Microstructure and mechanical properties of the coatings have been characterized. Erosion tests for different conditions using Air-jet erosion test rig for different impingement angles have been studied in detail. From these studies it is observed that satellite-6 coating exhibits lower erosive rate compared to other two coating materials. The morphology of the eroded surface shows craters, groove formation in the binder matrix and carbide pull-out as the existing erosion mechanism. Higher erosion loss is observed for Al2O3+CoCrAlTaY coating. © 2018 Elsevier Ltd.Item Erosion and Accretion in the Netravati River Stretch: Spatiotemporal Analysis Using Geospatial Approach(Springer Science and Business Media Deutschland GmbH, 2024) Makhdumi, W.; Shwetha, H.R.; Dwarakish, G.S.Understanding erosion and accretion, which are critical geomorphic processes, is essential for effective river management and conservation. Erosion by removing soil and rock changes the river's shape, depth, and course. Accretion, conversely, involves the deposition and accumulation of sediment, shaping features like riverbanks and floodplains. Focused on a 30 km stretch of the Netravati River, in the southwestern region of India, this study used Survey of India toposheets and Landsat images to track changes over time (1973, 1998, 2022). The Normalised Difference Water Index (NDWI) and image classification were employed for the analysis which revealed notable spatiotemporal variations in these processes. From 1973 to 2022, the analysis estimated a total erosion of 510.43 hectares and an accretion of 317.71 hectares. The years 1973–1998 witnessed more accretion (417.6 hectares) than erosion (229.08 hectares). And, from 1998 to 2022, erosion dominated at 438.37 hectares, with only 56.97 hectares of accretion. These variations can be attributed to both natural processes and human interventions. Notably, the construction of a vented dam in 1993 at Thumbe, followed by the subsequent dam in 2016, 50 m downstream of the old dam, influenced the sediment dynamics and flow patterns in the Netravati River, potentially impacting erosion and accretion processes. This research adds to our understanding of erosion and sediment changes in the Netravati River over time. The dams and hydraulic structure upstream along with geospatial techniques offer researchers and river managers a unique opportunity to examine river shape impacts and thus develop sustainable strategies for river preservation. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item The effect of the inclusion of ceramic particles in polythene material on the response to erosion due to impingement by sand particles at three angles is investigated. It is seen that erosion resistance varies with ceramic inclusions. The work also considers the limitations posed by the system in adopting weight change measurements as a measure to follow erosive wear owing to the softer nature of the matrix material. Consequently, the investigation looks at two other experimental parameters that can readily be measured to quantify erosion. Of the two approaches, the advantages of following wear through measuring linear dimension of the resulting crater is stressed in this work. The study also highlights the problems associated in assessing the depth of the crater as a parameter to express the extent of erosion owing to the phenomenon of material flow suggested and schematically illustrated in the work. Corroborative evidence for this flow behaviour through scanning electron microscopic studies is presented. © 2002 Elsevier Science Ltd. All rights reserved.(Elsevier Ltd, On evaluating erosion by sand particles in polythene system without and with ceramic particles) Kishore; Sridhar, G.B.2002Item Ocean wave transmission by submerged reef-A physical model study(2007) Shirlal, K.G.; Rao, S.; Rao, M.Ocean waves can be destructive as steeper waves due to their high energy eroding the sandy beaches. During storm surge or high tide, the water level rises and if large waves occur, they will break closer to the beach, releasing enormous amount of energy resulting in strong currents. This causes heavy loss of beach material due to large-scale erosion. If these waves are made to break prematurely and away from the beach, they can be attenuated so as to reduce beach erosion. The reef, which is a homogeneous pile of armour units without a core, breaks the steeper ocean waves, dissipates a major portion of their energy and transmits attenuated waves. This paper experimentally investigates the armour stone stability of the submerged reef and the influence of its varying distance from shore and crest width on ocean wave transmission. © 2007 Elsevier Ltd. All rights reserved.Item Integrated coastal zone management plan for Udupi coast using remote sensing, geographical information system and global position system(SPIE spie@spie.org, 2008) Dwarakish, G.S.; Vinay, S.A.; Dinakar, S.M.; Pai, B.J.; Mahaganesha, K.; Natesan, U.Coastal areas are under great pressure due to increase in human population and industrialization/commercialization and hence these areas are vulnerable to environmental degradation, resource reduction and user conflicts. In the present study an Integrated Coastal Zone Management Plan (ICZMP) has been developed for Udupi Coast in Karnataka, along West Coast of India. The various data products used in the present study includes IRS-1C LISS-III + PAN and IRS-P6 LISS III remotely sensed data, Naval Hydrographic Charts and Survey of India (SOI) toposheets, in addition to ground truth data. Thematic maps such as land use/ land cover map, bathymetry map, shoreline configuration map, transportation and drainage network maps, GPS survey map, CRZ map, contour map, DEM, inundation map, critical erosion area map were prepared. A Coastal Vulnerability Index has also been calculated for the study area to know the resistance of study area to sea level rise and is demarcated into four categories; Very high, High, Moderate and Low vulnerability, and a vulnerability map has been prepared. The results of the present study are encouraging. Some of the specific conclusions of the study are; about 50% study area is prone to erosion, river mouths along study area show shifting tendency towards south, and the beaches along the Udupi Coast are maintaining dynamic equilibrium. Coastal Zone Information System (CZIS) has been developed through V.B.6.0 using results of various data analysis. © 2008 Society of Photo-Optical Instrumentation Engineers.