Faculty Publications
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Item Hydraulic Modeling of River Discharge Subjected to Change in Riverbed Morphology(Springer, 2020) Kappadi, P.; Nagaraj, M.K.In natural channels such as rivers, the flow behavior is highly complicated phenomenon due to unsteady and nonuniform flow. Hydraulic modeling is essential for the study of characteristics of unsteady flow in rivers. Changes in riverbed morphology influence the increase in depth of flow in rivers. In the present study, the roughness coefficient is varied to match the natural condition. The objective of the paper is to study the effect of the change in riverbed morphology on the river discharge using a hydraulic model. The study is carried out using the Hydrologic Engineering Center—River Analysis System (HEC-RAS). A river length of 12 km of the Nethravathi river regime, Karnataka from Uppinangadi to Bantwal is considered for the study. Daily river stage and discharge data are collected from Central Water Commission (CWC) gaged at Bantwal station. GIS interface of HEC-GeoRAS is also used to extract the cross section, bed slope, and length of the river channel from Digital Elevation Model (DEM) data of resolution 30 m. The cross sections are represented for each kilometer length of the river. Since accurate data is unavailable in the study area, cross sections are simplified. HEC-RAS model was used for the simulation of surface water levels and discharge values. Manning’s roughness coefficient and river cross sections were defined for the calibration of observed river stage and discharge data. The predicted discharge was in good agreement with that of the observed discharge value. Study results illustrated that accuracy of predicted maximum water depth, and surface water level depends upon the precise representation of Manning’s roughness. The study is useful for the prediction of the flood dynamics in the river regime with the change in riverbed morphology. © Springer Nature Singapore Pte Ltd. 2020.Item Effect of grooves on the static strength of tubular T joints of offshore jacket structures(Elsevier Ltd, 2019) Murugan, N.; Kaliveeran, V.; Nagaraj, M.K.The present research work deals with effect of grooves on static strength and stiffness of tubular T joints of offshore jacket structures. Tubular structures are commonly employed in offshore jacket platforms due to better mechanical properties and economic advantages. The tubular T model considered for this study has chord dimensions of 1000 mm length, diameter 102 mm and thickness 5 mm and brace dimensions of 388 mm length, diameter 55 mm and thickness 4 mm. Material used for present analysis is Steel with Young's modulus of 210 GPa and the Poisson ratio of 0.3. Three-dimensional finite element analysis has been carried out to investigate the effect of grooves placed over thickened chord section on the static strength of tubular T joints subjected to axial compressive load. In the present study, unstiffened tubular T joint is analysed and compared with stiffened tubular T joints to observe the improvement in the static strength of the tubular T joints. The groove configurations considered are: 5 circumferential grooves at 16.5 mm spacing, 3 circumferential grooves at 16.5 mm spacing and 3 circumferential grooves at 33 mm spacing. The grooves were having the dimension of 1 × 1 mm, 2 × 2 mm were used for the analysis. The joint local stiffness of ungrooved tubular T joint is 116.43 N/mm. The grooved configuration increases the joint local stiffness by more than 250 percent. © 2019 Elsevier Ltd. All rights reserved.Item Flood estimation at ungauged catchments of western catchments of Karnataka, West coast of India(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2019) Amaranatha Reddy, N.A.; Seelam, J.K.; Rao, S.; Nagaraj, M.K.Many catchments in India are devoid of gauging stations. In the absence of measurements of stream flow, regional rainfall-runoff relationships developed over a hydro-meteorologically similar region may be used to estimate flood discharge at ungauged catchments. This study includes testing of different methods wherein a representative basin could be used to develop a Synthetic Unit Hydrograph (SUH) within its hydro-meteorological similar region. Derivation of SUH using Central Water Commission (CWC) flood estimation was tested on 13 catchments for Konkan and Malabar coasts on the west coast of India. The five methods are (i) CWC Dimensionless approach, (ii) Snyder method, (iii) SCS method, (iv) Two Parameter Gamma Distribution method and (v) Hybrid model. Inter-comparison of the SUHs and unit hydrographs derived from precipitation data is carried out. Amongst all methods tested the Two parameter Gamma Distribution method and Hybrid model satisfies the Unit Hydrograph criterion whereas, traditional methods of Snyder, SCS, CWC-SUH and CWC dimensionless methods require manual adjustments of the characteristics points and have a significant degree of subjectivity and trial and error. The above-said methods including CWC method are used to estimate flood discharge at ungauged catchments of the coastal districts along Karnataka coastline. © 2018, © 2018 Indian Society for Hydraulics.Item Performance of major ports using performance appraisal index(2007) Yaragal, S.C.; Nagaraj, M.K.Infrastructure plays a very important role in the economic progress of the nation. 90% of the international cargo is transported by the ships. In this view, the performance of ports plays an important role. The performance of the port should be assured based on multiple parameters. Such a study helps not only in comparing different ports based on performance, but also helps in corrective measures, identifying weakness areas and strengthening of key parameters. In the present study, a performance appraisal index for major ports is evolved using different parameters, to compare the efficiency of major ports in India. Important parameters are selected from the statistics of major ports in India. Sensitivity analyses are also performed, to evolve strategies for productive decision making for better performance.Item Combined optimisation simulation model for groundwater management policy options(2007) Yaragal, S.C.; Nagaraj, M.K.Water resources system being quite complex in-nature, modelling involves several variables and parameters. A large number of models have been developed for analysis of water resources system. Most of the models developed are of simulation optimisation type. In general water management models which generally use the governing partial differential equation of now, the problem is formulated using either finite difference techniques or finite element method. In this paper, a hybrid model is formulated which simulates the groundwater system and optimises the same. The model developed has been used to study the effects of variation in pumping factors on the optimal values and on the yearly yield from the system, for a chosen pattern of pumping. The model has been analysed for three different boundary conditions. The aquifer model is descritised into 64 grids and a particular pumping pattern is chosen in the present study. The governing partial differential equation for groundwater now is reduced to algebraic linear equations using finite differences scheme and they are then embedded as a set of constraints in the model. For the chosen pumping pattern, the pumping factor plays a key role, depending on the boundary conditions, in achieving an optimum solution. Here, minimisation of heads is considered for optimisation. The model helps in simulating a complex groundwater system and evaluating certain policy for groundwater management.Item Sensitivity of land cover parameter in runoff estimation using gis(2008) Nagaraj, M.K.; Yaragal, S.C.[No abstract available]Item Impact assessment of watershed development programme - A case study of Itagi watershed(2010) Palakshappa, K.; Nagaraj, M.K.; Shivapur, A.V.Soil, water and vegetation are the important gifts of nature to mankind. Welfare and development of mankind and its civilization revolves around conservation and development of these vital natural resources, which are so interdependent that one can not be managed efficiently without the other two. Watershed Development Programs (WDP) going on in India basically as soil and water conservative programs (as a policy response to the increasing environmental crisis and non-sustainability of agriculture especially in the dry land/semi-arid regions) has modified substantially with the introduction of watershed guidelines in 1994 by the Government of India. In the present study the area considered for assessment is Itagi sub watershed in Ranebennur taluk, Haveri district, Karnataka. During the watershed development programme soil and water conservation structures were constructed in the study area in the year 2004. The analysis of data reveals that there is an improvement in the groundwater recharge, increase in yield of the wells, increase in agricultural production, reduction in soil erosion and many other tangible and intangible benefits as a result of this watershed development programme. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Soil water holding capacity and its related properties for brackishwater shrimp farming along Dakshina Kannada District, Karnataka, India(2010) Varadaraju, S.; Nagaraj, M.K.; Badami, S.H.Selection of suitable site for aquaculture plays an important role in the success of shrimp farming since it is helpful in proper planning, designing, construction, operation and maintenance of ponds. Soil samples were collected from different locations along Dakshina Kannada District of Karnataka and selected physico-chemical parameters were analysed. The values of soil parameters recorded were: water holding capacity: 28.2 to 59.80%, bulk density: 2.03 - 2.27, pH: 4. 46 - 6.77, salinity: 0 - 2.95 ppt, organic matter: 1.53 -5.95% and permeability: 3.16 × 10-5-2.28 × 10 -7 cm sec-1. Textural class of the soil varied from sandy loam to sandy soil. Correlation analysis showed that the water holding capacity of the soil increased with the increase of silt, clay, density and organic matter. The water holding capacity decreased as the sand, voids ratio and porosity of the soil increased. The resuls of the present study suggests that the permeability of soils tested lie within the desirable range and suitable management practices are to be adopted in the case of sandy loam and sandy soil.Item Changes in soil and water quality parameters in selected shrimp culture ponds and its influence on shrimp production(2010) Varadaraju, S.; Nagaraj, M.K.; Badami, S.H.Changes in soil and water quality parameters during culture and its influence on growth of shrimps were studied in five shrimp culture ponds along the coastline of Udupi District of Karnataka. Water and soil properties of the ponds were within the permissible limits required for shrimp culture during the study period. An attempt made to correlate soil and water quality parameters with growth of shrimps revealed that water quality parameters namely pH, dissolved oxygen and temperature were found to be significantly affecting the shrimp production. Soil parameters viz., pH and electrical conductivity were found to be significantly influencing the growth of shrimps.Item Study on shelter effect of solid wind fences(2011) Umesh, U.; Prashanth, J.; Yaragal, S.C.; Nagaraj, M.K.In this paper the shelter effect of solid wind fence is investigated. A solid fence was considered with different bottom gap ratios (ratio of bottom gap to the height of the fence) of 0, 0.1, 0.2 and 0.3. The numerical analysis was done for different free stream velocities of 7.5 m/s, 10 m/s and 12.5 m/s. The results obtained were compared with the results of wind tunnel testing and flow visualization. Comparison between the experimental and numerical results showed a fairly good agreement. Flow visualization technique provided sufficient information for planning and conducting flow field measurements with a clear demarcation of reattachment length. The modified k- ? turbulence model predicted the flow well. From both the experimental and numerical investigation it is shown that a fence with gap ratio of 0.1 is effective in providing good shelter effect. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.