2. Thesis and Dissertations
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Item Gravity Wave Damping by Stratified Porous Structures(National Institute of Technology Karnataka, Surathkal, 2020) Venkateswarlu; Karmakar, Debabrata.In the present study, wave transformation due to multiple porous structures in the presence and absence of vertical rigid wall, barrier-rock breakwaters of various configurations, multiple horizontally stratified porous absorbers, vertically stratified porous structure lying on flat seabed, elevated seabed and stepped seabed is analysed under the oblique wave incidence. The eigenfunction expansion method using the continuity of pressure and velocity along with mode-coupling relation is adopted based on linearized wave theory. The direct analytical relations are derived for finding the wave reflection and transmission coefficients due to porous breakwaters of various structural configurations. In the preliminary stage, the analytical results are validated with numerical and physical model results available in the literature. As a special case, a comparative study is performed between the vertical rigid wall, permeable wall and stepped wall away from the double horizontally stratified wave absorbers. The vertical and stepped wall shows almost similar values of wave reflection at each of the resonating crests, but minimal values of the resonating trough in wave reflection is obtained from the stepped wall. A comparative study is performed between single and multiple porous structures of fixed structural width and depth. The 42% reduction in wave transmission is achieved with double porous structures as compared with single porous structure for uniform structural width, which may be due to wave damping in the free spacing available between the two structures. The distribution of incident wave energy in the form of wave reflection and transmission is effective in the case of horizontally stratified porous structure as compared with other structures. The vertically stratified porous structures performance is partially dependent upon structural width. Higher structural width effectively reduces the wave transmission as compared with conventional porous structures. The effect of each layer porosity, friction factor, structural width, incident wavelength, number of structures, angle of incidence, free spacing and trapping chamber effect on wave reflection, transmission damping, fluid force on seaward/leeward sides of breakwater and force on vertical wall is analysed for various types of porous structures. The critical angle due to standing waves, fluid resonance in the free spacing and clapotis has an efficient role in the design of porous structures.Item Hydroelastic Analysis of Floating and Submerged Flexible Structures(National Institute of Technology Karnataka, Surathkal, 2020) M, Praveen K.; Karmakar, Debabrata.The present work mainly deals with a class of physical problems in the broad area of wave structure interaction related to hydroelasticity. In the present study, the major emphasis is given • to analyse the hydroelastic behaviour of the very large floating structure based on the Timoshenko-Mindlin’s plate theory in both finite and shallow water depth, • to illustrate the significance of periodic array of articulation, change in bottom topography and wave attenuation due to the presence of vertical barriers in the hydroelastic analysis of floating structures which are of recent scientific interest in the field of Ocean and Coastal Engineering. In the present study, the generalized expansion formulae along with the orthogonal modecoupling relation is utilized to analyse the wave interaction with very large floating structure. The study is performed to analyse the influence of different edge support conditions on the hydroelastic behaviour of the floating elastic plate and the numerical results obtained based Timoshenko-Mindlin plate theory is compared with the EulerBernoulli plate theory. The gravity wave scattering by single and multiple articulated floating finite elastic plates are analyzed based on small amplitude linearized water wave theory. In the case of periodic array of multiple articulated floating elastic plates, the solution for the boundary value problem is analyzed by using both eigenfunction expansion method and wide-spacing approximation method. The transformation of gravity wave due to multiple variations in bottom topography in the presence of articulated floating elastic plate is studied by using orthogonal mode-coupling relation. Further, using shallow water approximation, the flexural gravity wave scattering due to (i) articulated floating elastic plates and (ii) abrupt changes in bottom topography are analyzed and the explicit relation for the wave scattering coefficients are obtained. Finally, surface gravity wave scattering due to the presence of vertical barriers along with the floating articulated elastic plate are analysed and the energy relation associated with transformations of gravity waves in the presence of vertical porous barrier is discussed. The numerical results for the reflection and transmission coefficients, plate deflection, strain along the floating elastic plate, bending moment and shear force are computed in different cases and analyzed.Item Soil Moisture Variability and Hydrological Impact Assessment of Land Cover Change(National Institute of Technology Karnataka, Surathkal, 2020) M, Diwan Mohaideen M.; Varija, K.Water availability in a region depends on how precipitation over the region is transformed into various forms after reaching ground such as evaporation losses, runoff, infiltration, soil moisture, and ground water storage etc. Land Use / Land Cover (LU/LC) changes adversely affect the aforementioned components. Particularly, the effects of LU/LC changes on catchment hydrological responses, especially vegetative cover (forest, scrubs and cropland), affect the evapotranspiration. Further, rapid urbanization due to LU/LC changes leads to extent of impervious surface and thereby, impacts the infiltration rates as well as recharge. The LU/LC change impact on the hydrologic system is region specific, and each region is characterized by its own hydrology, terrain, climate and also anthropogenic factors. Therefore, a detailed assessment of LU/LC change impacts on hydrology is required, specifically at the region with seasonally limited water availability. It is emphasized by many researchers that the physically-based, distributed hydrological models along with remote sensing capabilities are more suitable for assessing the LU/LC change impacts on the hydrologic system. Further, Soil moisture, being a critical state variable, its knowledge is of paramount importance in several hydrological applications (e.g., runoff modeling and flood forecasting, agricultural monitoring and drought monitoring). The magnitude of soil moisture variability often under estimated and the spatial pattern of soil moisture is not consistent, and it is largely varying across the site and climate with the influence of heterogeneity in LU/LC, topography, soil properties, precipitation and evapotranspiration. Hence, the characterization of soil moisture variability is essential. The work reported in this thesis aims at understanding the soil moisture variability and land cover change impacts in an agricultural dominant semi-arid basin. The Variable Infiltration Capacity (VIC) model, a physically based, semi distributed hydrological model was used to simulate the hydrologic responses of the basin for different LU/LC scenarios (the year 2000 and 2010) with multiple soil layersiv parameterization (three soil layers: 0 – 10 cm, 10 – 45 cm and 45 – 100 cm). The total drainage area of the basin was discretized into number of model grids (5.5 km resolution: totally 1694 grids), and the input parameterization of the model was made at each grid level. The major input parameters to the model are meteorological forcing (Precipitation, Tmax, Tmin), soil characteristics, land surface vegetation classes (vegetation parameter & library) and topography. This study demonstrated a methodological frame work for improved vegetation parameterization to the model simulation. Moderate Resolution Imaging Spectroradiometer (MODIS)-derived 8-day Lear Area Inded (LAI) time-series data was used to sub-group agricultural dominant areas into major crop groups and corresponding monthly vegetation phenology in terms of LAI, albedo, height, root distribution were arrived. This exercise enabled improved definition of vegetation parameterization for the study area, incorporating the region specific conditions. Firstly, the model was calibrated and validated using the observed stream flow data collected at two different locations for the period 1994 – 2001. The model parameter values were adopted for each model grid (about 5.5 km) based on the saturated hydraulic conductivity at that grid by trial and error method. To assess the hydrological impacts of LU/LC change on the flow regime of the basin, the model was run using the two LU/LC conditions separately with the same observed meteorological forcing and soil data. The changes attributed to LU/LC at basin level indicate that the surface runoff and baseflow decreased by 18.86 and 5.83% respectively. The evapotranspiration increased by 7.8%, mainly because of the agricultural crops. The variability in hydrological components and the spatial variation of each component attributed to LU/LC was further assessed at the basin grid level. The majority of the basin grids showed an increase in evapotranspiration (80 % of basin grids) and subsequent decrease in runoff and baseflow (79 and 85% of basin grids, respectively) with resepect to LU/LC change. Further, the spatio-temporal variation of soil moisture was assessed using the model simulated soil moisture along with three different satellite derived surface soil moisture products (SM-CCI, SM-TRMM and SM-AMSRE). It was found from the analysis that the impacts of LU/LC changes on soil moisture were more evident in the deeper layers (45 cm and 100 cm). The soil moisture decreased byv an average of 14.43 and 18.21% (percentage change), particularly in dry periods at second and third layers, respectively. Further, the modeled soil moisture along with three different satellite surface soil moisture products were investigated for its spatio-temporal variability in the basin. The soil moisture in the top layer (up to 10 cm) showed high temporal variations. However, the mean soil moisture was found almost constant during the summer and winter seasons. The basin showed high variability in soil moisture during the intermediate wetness condition. Further, the spatial variability of the soil moisture during the wetting period (June-August) was high compared to drying period (December – February). Based on the analysis performed in this study, 29 (out of total model grids - 1694) representative grid locations were identified in the basin. These locations could be effectively considered for installing observational network mainly for monitoring soil moisture in near real-time.Item Modeling Evapotranspiration using Remotely Sensed Spatial Contextual Information(National Institute of Technology Karnataka, Surathkal, 2020) C, Sanjay Shekar N.; Nandagiri, Lakshman.Characterization of the spatial and temporal variabilities of Actual Evapotranspiration (AET) or Latent Heat Flux (λET) from heterogeneous landscapes is essential in studies related to hydrology, climate, agriculture, irrigation, water resources engineering and management and environmental impact assessments. AET/λET is influenced by a large number of factors related to climate, vegetation and soil moisture and therefore its direct measurement is rendered difficult especially over large spatial domains. The only feasible and convenient way to map AET over regional or catchment-scales is through the use of remote sensing technology and accordingly, numerous world-wide studies have focussed on this approach. Among these, the Penman-Monteith (PM) and Priestley-Taylor (PT) methods have proved to be most popular on account being simple but yet providing reasonably accurate estimates of regional AET. However, most previous studies have implemented satellite-based PM and PT AET estimation approaches to crop lands located in arid to semi-arid regions. Therefore, the main focus of the present study is to develop satellite-based AET estimation methods which can be applied to wet tropical regions possessing natural vegetation. The current research work is aimed at the development, application and evaluation of methodologies for estimation of AET/λET by the PM approach using Moderate Resolution Imaging Spectrometer (MODIS) satellite imagery. The feasibility of extracting the bulk surface conductance (Gs); an important parameter in the PM model, from the spatial contextual information present in a scatter plot of Land Surface Temperature (LST) versus Fraction of Vegetation (Fr) is explored in this study. Also, few studies seemed to have compared the performances of the PM and the PT model and other similar models using the same dataset and therefore this exercise was taken up. Using a general expression for Gs derived by assuming a two-source total λET (canopy transpiration plus soil evaporation) approach proposed by previous researchers, minimum and maximum values of Gs for a given region can be inferred from a trapezoidal scatter plot of pixel-wise values of LST and corresponding Fr. Using these as limiting values, Gs values for each pixel can be derived through interpolation and subsequently used with the PM model to estimate λET for each pixel. The proposed methodology was implemented in 5 km x 5 km areas surrounding each of four AsiaFlux tower sites located in different countries of tropical south-east Asia which were selected based on certain specific criteria. MODIS data products of MOD11A1 product of Land Surface Temperature (LST) at 1000 m resolution, MOD09GA product of Land Surface Reflectance (LSR) at 1000 m resolution, MOD15A2 product of Leaf Area Index (LAI) as eight days average composited at 1000 m resolution and Digital Elevation Model (DEM) at 30 m resolution were used. Preliminary processing of images was performed using MODIS reprojection tool (MRT) and was converted to a standard format that can be read by MATLAB software. Geo-referencing, subsetting and pixel-wise analysis corresponding to the study area were performed using ArcGIS and ERDAS IMAGINE. Model evaluation was carried out using the following performance measures- coefficient of determination (R2), root mean squared error (RMSE), percent bias (PBIAS) and the intercept (a) and slope (b) terms of a linear regression fit (y = a + bx). Excellent comparisons were obtained between tower measured λET and those estimated by the proposed approach for all four flux tower locations (R2 = 0.85 – 0.96; RMSE = 18.27 – 33.79 W/m2). The proposed methodology was compared with two alternative methods proposed by previous researchers. Performances of all three approaches were comparable indicating the robustness of the methodology proposed in the present study. The PM method proposed in the present study was implemented in the Hemavathi sub-basin which is located in the Cauvery River Basin, Karnataka, India to map spatial patterns of daily AET. MOD16A2 product of actual evapotranspiration (AET) as eight day average composited at 500 m resolution was used for validation purposes. Climate records for the Belur station were used. The analysis was carried out for two dates in summer and two dates in winter separately for the years 2007 (wet year) and 2012 (dry year). For each date, trapezoidal scatter plots of MODIS-derived LST values versus Fr were plotted by considering 1 km2 pixels in the study area of 304 km2. For each day, estimated AET values by the PT approach (AETPT), PM model of the present study with Ga computed using Leuning equation (AETPM) and with Ga computed using Choudhary equation (AETPMCH) for each of the 304 pixels were extracted and compared with the corresponding pixel-wise MOD16A2 ET estimates. Results of the performance evaluation of AET estimation methods relative to MOD16A2 showed that the PM model proposed in the present study with Ga computed using the Leuning equation (AETPM) performed reasonably well for both the wet and dry years. High values of R2 (0.77 – 0.90) and reasonably low values of RMSE (0.28 – 0.38 mm/day) were obtained but the PBIAS values were somewhat high (-7.04 – -12.41). Also, the PM model yielded relatively poorer estimates for the winter days of the drier year 2012. The performance of the PT model was quite similar to the PM model with similar performance statistics being recorded. However, slightly lower RMSE values were obtained for this model on some days. The PM model proposed in the present study with Ga computed using the Choudhary equation turned out to be the best model as indicated by the lowest values of RMSE (0.19 – 0.25 mm/day), although R2 values were similar. Also, use of the Choudhary equation reduced PBIAS values significantly for all days considered. Using the pixel-wise values of AETPMCH, maps showing the spatial variability were prepared for the Hemavathi sub-basin for all the dates considered in 2007 and 2012. The variations of AET over the basin appear to be influenced by topography, type of LU/LC, LST and moisture availability conditions. The satellite-based spatial contextual information approach adopted in the present study for the first time with the PM model has proved to be a simple, calibration-free and accurate method. As demonstrated by previous studies and also the present study, use of the LST-Fr plot does not require additional hydrological data for optimization of the AET model parameters. The framework for implementing the spatial contextual information approach to derive operational estimates of daily AET over large spatial domains has been developed and validated in this study.Item Characterization Of Historical and Future Hydrometeorological Droughts in an Indian Tropical River Basin(National Institute of Technology Karnataka, Surathkal, 2020) Pathak, Abhishek A.; Dodamani, B M.Drought is acknowledged as a significant natural disaster which leads to food, fodder, and water shortages along with destruction of vital ecological system. Drought is a transient recurring sinister disaster, which originates from the lack of precipitation and further creeps into different subdivisions of hydrological cycle causing adverse effects on agricultural and its allied sector. Combination of these leads to economic losses and several damage to living organisms. Identifying and quantifying drought characteristics of a region is must to understand the behavior of drought and its profound impacts on society, economy, and environment. Along with the historical knowledge, comprehensive overview of future drought projections is a vital step in ensuring future water and food security. The present study focuses on characterizing different hydrometeorological droughts in the historical and future climate of an agrarian Indian river basin. The specific objectives of the study are 1) To investigate annual and seasonal trends of hydro meteorological variables, over the study area. 2) Assessment and comparison of Meteorological, Hydrological and Agricultural drought characteristics with multiple indices 3) To explore the applicability of copulas theory for joint modeling of drought characteristics 4) Characterization of future hydro-climatic droughts. The study was implemented in the Ghataprabha river basin, being one among the potential lands for agriculture in the basin of river Krishna. Firstly, the basin has been categorized in to humid, sub humid and semiarid region based on Aridity Index. Similarly, groundwater well of the study area are grouped in to different clusters using hierarchical and non-hierarchical clustering methods The annual and seasonal trend analysis of different hydrometeorological variables are carried out using Mann-Kendall trend test and the magnitude of the trend was estimated using the Sen’s Slope Estimator. A non-significant decreasing trends in both rainfall and rainy days was observed in semiarid region during monsoon period. Significant increasing trend in mean temperature was observed for all the stations and for all the seasons with the average magnitude of 0.2⁰ C per decade. Along with the mean temperature, annual andseasonal PET trends were also increasing for all the stations but are significant only in semiarid region with the average increase of 3.5mm per decade. The trends in annual streamflow of the basin are decreasing with magnitude of 574.25 cumecs/year, whereas, no significant trends were observed in the reservoir levels. The trend analysis of the groundwater levels of different clusters, revealed that annual water level in the 81% of the wells of cluster 2 and 47% of the total wells of the study area are significantly declining. The hydrometeorological droughts assessment with different indices portrayed significant number of droughts in the past. The RDI and SPI are behaving similarly in all the stations whereas, significant discrepancies was observed between SPI/RDI and SPEI. The hydrological drought assessed with SDI followed similar pattern with SRSI whereas it showed significant divergence with meteorological droughts. Similarly, Agricultural drought derived through VCI followed similar pattern of SPI-6 in comparison with SPI-3. A teleconnection between meteorological drought and groundwater drought was observed along with the crucial role of underlying hydrogeological characteristics. Joint modelling of hydrometeorological drought characteristics and regional bivariate frequency analysis was carried out by employing Archimedean copula. An attempt has also been made to characterize drought in multivariate perspective by developing Standardized Hydro Meteorological drought Index. From the results of bivariate frequency analysis of meteorological drought, it was observed that, droughts of high severity with prolonged duration are frequent in semiarid region compared to humid and sub-humid regions. The joint probability of hydrological drought conveyed drought of smaller duration or severity are more prominent in the basin whereas joint return periods of groundwater drought is high in the well of cluster 2. The developed SHMI considers combined effects of precipitation and streamflow to picturize a near realistic drought scenario of the basin. The future hydrometeorological drought characteristics were assessed by different RCMs. The different bias correction methods were applied to rainfall and temperature to raw RCMs and observed that CNRM-CM5 with LS bias correction method performed better for correcting the rainfall and VS is proved to be superior for correcting the temperature projections. The trend analysis carried out for the future hydrometeorological variable showed significant decreasing trends in annual and post monsoon season whereas temperature trend is increasing significantly with the rise of 0.150 C per decade. The future hydro-meteorological drought characteristics revealed that the basin will experience more number of droughts compared to the past and it can be attributed to decreasing rainfall trend and significant rise in temperature of the basin. In this study, an attempt has been made to characterize future and historical hydrometeorological droughts comprehensively. The outcome of the study will be helpful to design proactive drought mitigation and preparedness strategies for upcoming drought and it also provides a framework to evaluate the drought risks at other parts of the world.Item Shoreline Dynamics In Response To River Sediment: A Case Study(National Institute of Technology Karnataka, Surathkal, 2020) Yadav, Arunkumar.; Dodamani, B M.; Dwarakish, G S.The coastal zone of Karwar is acquiring increasing importance due to its rich ocean resources and favorable conditions for the development of port-based industries, defense activity, tourism, fisheries, and small scale industries. Rivers and its networks are the major sources of the sediments, which supplies to the coast. These sediments are responsible for beach nourishment and shoreline configuration. The present study is carried out with a view to study the long-term shoreline configuration with the response to pre-construction dam and post-construction of the dam, to study the seasonal variation on shoreline configuration, to investigate the change in Kali estuary to assess the impact of the dam on sediment yield, To understand the sediment dynamics of beach face sand using granulometric method and To quantify the seasonal coastal process in terms of beach sand volume. These objectives are addressed using various conventional data, related tools, and freely available satellite data. Kali river basin, Aghanashini river basin, Karwar coast and Aghanashini coast along the west coast of India is the study area. There are five dams constructed across the Kali river basin for hydel power purposes. The presence of these reservoirs regulates stream flow and thus sediment load in the basin. However, the free flow of water across the catchment of the Aghanashini river leads to the unobstructed or natural passage of sediments and sediment budget to the downstream and the river mouth, as the catchment is not disturbed by the reservoir. Survey of India toposheet was used to prepare the base map. A conceptual, continuoustime and semi-distributed, SWAT2012 (Soil and Water Assessment Tool) model was selected for the sediment yield analysis. Dam location and dam discharge data were one of the major inputs for the model to estimate the sediment yield. Simulated and observed values of runoff are compared, and calibration and validation were done for the basins using SWAT CUP. The long-term shoreline configuration was carried out using LANDSAT satellite products only. The predominant direction of sediment transport was determined by drawing sediment trend matrices based on the statisticalviii parameters of beach face sediments. To understand the change in Kali estuary a portion of Devabag beach, satellite data were used for the duration from 1975 to 2018. The Total Station survey was carried for Ravindranath Tagore beach and Devabagh beach of Karwar coast, including a seasonal wise profile survey and cross-section survey during 2017. Based on the present analysis of sediment yield, it is concluded that the Sediment yield obtained at the catchment outlet was 1.39t/ha/year and 4.58t/ha/year for the Kali river and Aghanasini river basins respectively. It was observed that the decline in sediment load in the Kali river basin compared to the Aghanashini river basin indicates that the influence of reservoir operation on streamflow and sediment yield. The analysis to study the long-term shoreline configuration with the response to the pre-construction dam and post-construction of the dam, shows that shoreline of the Karwar coast was having accretion and later, it is turned in to erosion zone due to postconstruction of the dam. It shows the importance of natural river flow. Shoreline change analysis on the Aghanashini coast shows the accretion zone due to the natural flow of the Aghanashini river to the coast. The study estuary change shows that for the period of 1975 to 2018 northern part of the estuary has lost area and construction of seawall was revealed from ground truth data. Beach profile studies by total station on Ravindranath Tagore beach reveals that beach profile changes according to the season. The volume of sand is decreased during the pre-monsoon season and increased during the post-monsoon season. The accuracy of all the results can be increased by an increase in a number of inputs in the case of SWAT tool, the accuracy of results obtained from the satellite can be increased by higher resolution data. From the study, it is concluded that the river and its network are the major sources for the sediment supply to the coast. Sediment is one of the major factors for beach nourishment. Dam influences the flow of the river and its network and reduces sediment supply to the coast. A natural flow of the river and natural supply of river sediment enhances the beach nourishment and maintains the equilibrium of sediment budget to the coast.Item Soft computing techniques in the prediction of performance of semicircular breakwaters(National Institute of Technology Karnataka, Surathkal, 2020) Kundapura, Suman.; Rao, Subba; Hegde, Arkal Vittal.In the dynamic environment of the coast maintaining the harbor tranquility is possible only with the planning of proper protection structures. Breakwaters are one among the several coastal protection structures. Breakwaters could either run into the water linking to the shore or placed independently parallel to the shore. The former will lead to the accretion on up drift side and erosion on the down drift side of the structure but the latter provides shore protection without adversely affecting the longshore transport. Breakwaters attenuate the wave, slow the littoral drift and produces sediment deposition. To provide a basis for evaluating the effects of breakwater installation a comprehensive study on the hydrodynamic response of breakwaters needs to be investigated. Physical models could be used in the laboratory to assess the same however, it is expensive, laborious and time-consuming which involves many variables that affect the shape, strength, alignment, base stability and other phenomena. There are several empirical formulae but developed on limited data. Also, though numerical models are good option, it involves numerous assumptions not withstanding faster computing resources, most of which are time-consuming, tend to overestimate the hydraulic responses. The Computational Intelligence (CI) techniques can be made use to overcome some of these shortcomings. As they are capable of replicating the outcome of a numerical model with better accuracy. Among the several breakwaters available, the emerged semicircular breakwater is found advantageous and also the study on this type of breakwater is limited. Hence the present study is taken up to predict the hydraulic responses like reflection coefficient, relative wave runup, stability parameter, of emerged seaside perforated semicircular breakwater using different soft computing techniques. The soft computing techniques used are Artificial neural network (ANN), Adaptive neuro-fuzzy inference system (ANFIS), Genetic algorithm based adaptive neuro fuzzy inference system (GA-ANFIS) and Particle swarm optimization based adaptive neuro fuzzy inference system (PSO-ANFIS). The prediction is done using conventional data segregation method. Also, a methodology of segregating the lower ranges of wave height data, and not using it for training the network and then predicting the hydraulic responses purely for this segregated data is done successfully and it is namedii as ‘below the range’ predictions. Similarly, a prediction for purely higher ranges of wave height data not used in training the network, has been carried out and it is named as ‘beyond the range’ prediction. The study shows the possibility of prediction of the hydrodynamic characteristics like reflection coefficient, relative run-up parameter and stability parameter of the semicircular breakwater using the soft computing techniques for both dimensional as well as non-dimensional input parameters. In both the cases the predicted outputs the reflection coefficient, relative run-up parameter and stability parameter was good in the conventional data segregation case. Also, below the data range approach gave reasonably good results in both set of input parameters for the prediction of reflection coefficient. Whereas, in the case of beyond the data range predictions the results are good in the case of dimensional input parameters but not for non-dimensional input parameters in the prediction of reflection coefficient. The relative wave run-up parameter prediction for below and beyond the range predictions did not give satisfactory results for both set of input parameters. In the present study the stability parameter of emerged seaside perforated semicircular breakwater is predicted for a dataset of 389 data sets. The results found are good for both the set of input parameters in the case of conventional data segregation method. As the available dataset is only 389 data sets, the below the data range and beyond the data range approach was not done for stability parameter prediction. From the performance of four different models in several cases considered, the prediction made by GA-ANFIS gave better results in maximum number of cases. The ANN also predicted the output parameter well, though it is an individual model. But, the disadvantage here is the number of neurons in the hidden layer is chosen based on trial and error method, depending on thumb rules. In the case of ANFIS method the FIS could be generated by grid partitioning, subtractive clustering or fuzzy cmeans clustering. In the present study since the number of inputs in dimensional as well as nondimensional case is more than 5 the grid partitioning method has not been employed as it suffers the curse of dimensionality. In such cases the subtractive clustering or fuzzy c-means clustering can be employed. In the study it is found that the prediction made by fuzzy c-means clustering-ANFIS gave better results in maximum number of cases of reflection coefficient prediction compared to subtractive clustering-ANFIS with dimensional input parameters. Hence for all the remaining cases FCM-ANFIS is employed. The performance of PSO-ANFIS model is not as good as GA-ANFIS in the different cases considered. Arriving at the optimal parameters of the hybrid model costs time.iii However, these soft computing techniques can be adopted as an alternate technique to predict the hydraulic response of semicircular breakwaters by coastal engineers when similar site conditions are available.Item Buckling Analysis of Offshore Pipeline with Various Buckle Arrestor Configurations under Static Axial Load(National Institute of Technology Karnataka, Surathkal, 2020) Rao, N Ramachandra.; Kaliveeran, Vadivuchezhian.During the last three decades, offshore oil and gas exploration and production has ventured into deeper seas as many shallow water fields are already exhausted. Today the production has reached ocean depth of approximately 7,000 ft., while exploration for oil resources is conducted at depths of 11,000 ft. With the development of oil and gas fields in different parts of the world, such as Gulf of Mexico (U.S.), North Sea, Southeast Asia, Brazil, Mediterranean Sea, Persian Gulf, Middle East, South China Sea, Australia etc., the economic importance of offshore pipelines can be gauged by the fact that around a third of the oil and gas extracted worldwide comes from offshore resources. Offshore pipelines are major components used by oil and gas industry for drilling, production and transmission. As a result of the greater depth of oil exploration, offshore pipelines are subjected to several forces such as pressure (internal and external), temperature, axial force acting on pipelines due to the difference between the temperature of material carried and ambient temperature and interaction of the pipelines with the surrounding material. The external forces acting on the pipelines result in buckling of offshore pipelines. Free spanning of offshore pipelines subjects them to bending forces. Offshore pipelines are subjected to lateral buckling, upheaval buckling which causes disruption of offshore facilities and interrupts the supply of oil. Therefore, buckling of offshore pipelines should be controlled within permissible limits. Several methods are employed to control buckling and ensure uninterrupted functioning of offshore pipelines. Use of buckle arrestors, advanced materials and latest techniques such as use of sensors to monitor offshore pipelines are the methods adopted to control buckling. Current research work focuses on the improvement in structural properties of offshore pipelines stiffened with buckle arrestors of different configurations and placed at different locations along the pipeline. Finite element modeling was performed, and experiments were conducted on pipeline models made of stainless steel of grade SS304 which is suitable for offshore applications. Finite element analysis of offshore pipeline models stiffened with buckle arrestors of different configurations was performed to understand significance of varying length and placement of buckle arrestors. The optimum length of buckle arrestors was identifiedii from finite element analysis, and pipeline models were fabricated for conducting experiments. Comparison of finite element analysis results and experimental outcomes showed that the efficiency of buckle arrestors increased by increasing the dimensions and location of buckle arrestors. Three point bending experiments were conducted on the pipeline models to determine flexural capacity of the pipeline models.Item Mechanical Characterization of Arecanut Husk Fibre Composites Panels Under Static and Dynamic Loading Condition(National Institute of Technology Karnataka, Surathkal, 2020) Muralidhar N.; Kaliveeran, Vadivuchezhian.Arecanut husk fibre is an agricultural waste, which does not contribute to the economy of arecanut plantation. The use of arecanut husk fibre as reinforcing material in the preparation of low cost and low density composite panels provides usability to arecanut husk. Low cost and low density composites have wide range of applications in construction industry, marine structures, automobile industry and aerospace industry. The present work focuses on extraction of arecanut husk fibre with alkali treatment process by using 6 % of sodium hydroxide solution, composite panel preparation and determination of mechanical properties of composite panels under static and dynamic loading condition. Different fibre compositions (fine fibre, coarse fibre and coarse fibre sandwiched with glass fibre) of 15 % by weight were used in the present study. The tensile strength of composites made with fine fibres (15.1 MPa) was observed to be more than that of composites made with coarse fibres (10.8 MPa). Further improvement in tensile strength of composite panels made of coarse arecanut husk fibre layer sandwiched with two layers of glass fibre (24.8 MPa) was observed. The flexural strength of fine fibre composites was more when compared to that of the coarse fibre composites. The average flexural strength of composites reinforced with fine fibre, coarse fibre and coarse fibre sandwiched with glass fibre were observed as 85 MPa, 65 MPa and 240 MPa respectively. The coarse fibre composites resulted in higher impact strength when compared to fine fibre composites. Dynamic mechanical analysis, shows trend of storage modulus increased with increase in loading frequency and variation of increment in storage modulus decreased with increase in frequency. At room temperature, the values of storage modulus are 0.478 GPa, 0.573 GPa and 0.607 GPa for loading frequencies of 5 Hz, 10 Hz and 15 Hz respectively. The arecanut composite can retain its storage modulus up to 80 °C. The glass transition temperature of arecanut husk fibre composites is 105 °C.Item Asymmetric Relationship of Nino Indices with Rainfall Extremes over Western Ghats and Coastal Region of Karnataka(National Institute of Technology Karnataka, Surathkal, 2020) C, Vinay D.; Shetty, Amba.Climate variability and change has increased extreme rainfall events. There is an underreporting and limited analysis, which often have significant impact with extreme rainfall events at regional scale. The magnitude of variability of the rainfall extremes varies according to locations. Among subdivisions of Western Ghats of India maximum rainfall occurs over Coastal Karnataka. Examining the extreme events of rainfall provide an idea of the probable occurrence of severity conditions in future in the context of changing climate. Extreme rainfall indices to identify the variation of rainfall patterns such as the number of rainy days, total rainfall, daily intensity index, one and five-day maximum rainfall, dry spells and threshold intensity rainfall frequency indices were considered as per the norms suggested by Expert Team on Climate Change Detection (ETCCDI) of Intergovernmental Panel on Climate Change (IPCC). These rainfall extremes indices are analyzed using IMD gridded high resolution daily rainfall data for the period 1901-2013. Statistical trend analysis techniques namely Mann–Kendall test applied for extreme rainfall indices and Theil-Sen estimator perceive nature and magnitude of slope in rainfall indices. The trends show contrasting spatial variations of extreme rainfall indices in Coastal region (low land) and Western Ghats (high land) regions of Karnataka. The changes in daily rainfall events in the lowland region primarily indicate statistically significant (varies from 95% to 99.9% confidence level) positive trends in the annual total rainfall, 1-day, and 5-day maximum rainfall, frequency of very heavy rainfall, and heavy rainfall as well as medium rainfall events. The seasonal variation of rainfall exhibits mixed trend, however significantly rising trend is witnessed in the southern coastal plains and the adjacent Western Ghats region during the pre-monsoon. But, southern coastal plains show a decreasing trend in the monsoon period (JJAS). Furthermore, the overall annual rainfall strongly correlated with all the rainfall indices in both regions, especially with indices that represent heavy rainfall events which are responsible for the total increase of rainfall. The interannual variability of rainfall and its extreme events over study region is observed to be associated with ENSO cycle, whereas Nino indices are asymmetric over the study region. The trends in ETCCDI extreme rainfall indices analyzed as an issue of climate change and the possible teleconnection with the ENSO mode as a concern of natural climatic variability have been analyzed over the study region. Nevertheless, differences are foundii between the spatial extent of correlation coefficients and their magnitudes. Using most significant time lag between the extreme rainfall indices (dependent variable) and the November-January (ONDJ) seasonal average of Niño indices (independent variable). The best model with the highest coefficient of determination was identified by Step wise regression analysis. The teleconnection between the Niño indices (Niño 1+2, Niño 3, Niño 3.4 and Niño 4) and the rainfall extremes with 0-year and 1-year ahead are at different phases, regional response of rainfall extremes to these indices are dissimilar. This analysis provides insights into regional response of rainfall extremes to global climate indices over the study region. The large-scale phenomenon over the pacific ocean with rainfall over the study region provide a scientific basis for understanding and developing credibility in future regional climate. A significant lag correlation between the summer monsoon rainfall and Niño indices was revealed by the seasonal lead-lag correlation analysis, Niño 3(t-4) at 90% confidence level, remaining Niño 3.4(t-2), Niño 4(t-2), and Niño 4(t-3) at 95% confidence level shows a significant relationship at respective lag period from onset of summer monsoon rainfall. In order to investigate the combined lagged effects of the potential climate predictors for monsoon rainfall using multiple linear regression as a linear method compared to neural network as a nonlinear method have been employed to examine the predictability of the summer monsoon rainfall. The principal component analysis of predictors aids to represent in one-dimensional space using the eigen vector that corresponds to the covariance matrix’s largest eigen value. Whereas first principal component explains about 72% of the variance of the predictors. Thus, PC1 considered as predictor in regression equation and input layer in neural network models to avoid over fitting. The attained prediction on the basis of the overall performance of the prediction models, feed forward neural network model shows a better prediction compared to other models with a good correlation coefficient and RMSE of 0.53 and 1.6 for training case, and 0.72 and 1.63 for testing case, respectively. From the time series analysis for period 1951-2013 of standardized monsoon rainfall Index selected the positive episodes values having standardized value greater than +1 (excess) and similarly with negative episodes values with standardized values less than -1 (deficit). The mean anomalous SST values for the region Nino 3.4 for the season DJF (- 2) for positive episode is 0.1719oC and the negative episode is -0.5133oC. The two SST means are significantly different at confidence level of 87.15% through the Student’s t-test.iii In awaken of climate change, this study is a contribution in the on-going research of extreme events over mountainous terrain including disaster management study. The sequential daily rainfall extremes and other atmospheric parameters may be utilized for the now-casting of extreme rainfall events. Further the relationship between topography and other atmospheric parameters influence for rainfall extremes should be studied separately to get better insight. This research may also be useful for the modifications in rainfall extremes retrieval methods over the Western Ghats mountainous terrain.