Faculty Publications
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Item On numerical modelling of waves, currents and sediment movement around Gurupur-Netravathi river mouth(2010) Radheshyam, B.; Rao, S.; Shirlal, K.G.This paper presents an overview of the investigations that were carried out to understand the coastal process along Bengre and Ullal at the Gurupur-Netravathi River mouth in the west coast of India. This river inlet was facing problems of migration and siltation since several decades and therefore two rubble mound breakwaters were constructed during the year 1994 as an intervention to maintain the inlet mouth. After the construction of these river training jetties, the inlet was stabilized, but severe erosion has been taking place along the Ullal spit on the south side of southern breakwater, since 1996 and heavy accretion on the North of Northern Breakwater along Bengre spit, which is now almost stabilized. This study has been undertaken to understand the hydrodynamics along the beaches adjoining the river mouth. For the present study, various field data was collected for the post monsoon season of 2006. The hydrodynamic (HD), Parabolic mild slope (PMS) and Sediment transport (ST) modules of MIKE-21 software were used to understand the hydrodynamics of the study area. Before the model was made use, it was first validated by using field data to understand the hydrodynamics of the area. Since the field data is of limited duration, data collected from the NMPT wave buoy for an entire year was used for the model simulation. From the studies it was confirmed that current direction and sediment movement follow a similar pattern in monsoon and pre-monsoon and a different pattern during post-monsoon. It is observed that the main cause of erosion is due to direct action of waves on the adjoining beaches of the coast and the beaches in the study area are generally in dynamic equilibrium with a small amount of erosion at Ullal. © 2010 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Variation of transmission coefficient and mooring forces with wave steepness on horizontal interlaced multilayered moored floating pipe breakwater with three layers(2011) Rajappa, S.; Pramod, K.; Hegde, A.V.; Rao, S.The paper presents the results of a series of physical model scale experiments conducted for the study of the transmission characteristics and mooring forces of horizontal interlaced, multi-layer, moored floating pipe breakwater, part of which have been presented in conferences. The studies are conducted on physical breakwater models having three layers of PVC pipes, wave steepness, Hi/L (Hi is incident wave height and L is incident wave length) varying from 0.01384 to 0.0661, relative width, W/L (W is width of breakwater) varying from 0.4 to 2.65 and relative spacing, S/D = 3 (S is horizontal spacing of pipes and D is diameter of pipe). The transmitted wave height is measured and data gathered is analyzed by plotting non-dimensional graphs depicting the variation of Kt (transmission coefficient) with Hi/L for values of d/W (d is depth of water) varying between 0.082 to 0.276 and Kt with W/L for values of d/W varying between 0.082 to 0.221. It is observed that Kt marginally decreases as Hi/L increases for the range of d/W between 0.082 and 0.221, considered in the present study. The maximum wave attenuation achieved with present breakwater configuration is 68%. The variation of measured mooring forces are analyzed by plotting non-dimensional graphs depicting fs/?w2 and fl/?W2 (fs and fl are the forces in the seaside and leeside moorings per unit length of the breakwater, ? is the unit weight of sea water) as a function Hi/L for various values of d/W. The mooring force parameter (fs /?W2) increases with an increase in wave steepness (Hi/L) for a range of d/W values studied. It is observed that for d/W = 0.082, maximum force parameter attained was 2.11E-04, and for d/W = 0.276 maximum force parameter was 6.88E-04. A similar trend is observed for leeside side force parameter. Hence, it clearly indicates the influence of d/W on f/?W2. © 2011 CAFET-INNOVA technical society. All right reserved.Item Wave steepness and relative width: Influence on transmission coefficient of horizontal interlaced, multilayered, moored floating pipe breakwater with five layers(2011) Rajappa, S.; Hegde, A.V.; Rao, S.; Channegowda, V.This paper presents the results of a series of physical model scale experiments conducted to determine the transmission characteristics of a horizontal interlaced, multilayered, moored floating pipe breakwater. The studies are conducted on physical breakwater models having five layers of PVC pipes. The wave steepness (H i/gT 2, where H i is incident wave height, g is acceleration due to gravity, and T is time period) was varied between 0.063 and 0.849, relative width (W/L, where W is width of breakwater and L is the wavelength) was varied between 0.4 and 2.65, and relative spacing (S/D, where S is horizontal centre to centre spacing of pipes and D is the diameter of pipes) was set equal to 2. The transmitted wave height is measured, and the gathered data are analyzed by plotting nondimensional graphs depicting the variation of K t (transmission coefficient) with Hi/gT 2 for values of d/W (d is depth of water) and of K t with W/L for values of H i /d. It is observed that K t decreases as H i /gT 2 increases for the range of d/W between 0.082 and 0.139. It is also observed that K t decreases with an increase in W/L values for the range of H i /d from 0.06 to 0.40. The maximum wave attenuation achieved with the present breakwater configuration is 78%.Item Reshaping berm breakwaters: A physical model study(National Institute of Science Communication and Policy Research, 2018) Janardhan, P.; Rao, S.; Shirlal, K.G.In the present study, the structural stability of statically stable reshaping berm breakwater for different wave parameters and armour weights were verified by physical model study carried out at NITK Surathkal Mangalore. Wave run-up and rundown studies were also carried out. The results show that a safe structure can be evolved with reduction in armour weight by up to 25% for all the relative berm position values. The position of berm greater than or equal to 1.3 was found to be good in reducing recession as well as wave run-up. An empirical new berm recession formula was derived for berm recession based on sea state and structural parameters. © 2018, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.Item Long-term analysis of waves off Mangaluru coast(National Institute of Science Communication and Policy Research, 2020) Upadhyaya, S.K.; Rao, S.; Rao, M.A competent coastal engineer should have adequate knowledge with regard to wave analysis. Long-term analysis is being effectively used worldwide to predict wave heights based on extreme wave statistics. The objective here is to analyze the ocean waves off Mangaluru coast, India. Long-term analysis is initially performed based on probability distributions like Log-normal distribution, Gumbel distribution, Fretchet distribution, Exponential distribution, and Weibull distributions on the in-situ wave data recorded at coastal waters off Mangaluru coast. The Extreme wave analysis is performed based on Peak Over Threshold method from which the best-fit probability distribution is obtained. Further, the best performing distribution is applied on the simulated wave heights obtained from MIKE 21 numerical model forced with ERA-interim wind speed data of 38-years. From the analysis, amongst the five different distributions considered Weibull distribution with ? = 1.3 gave the best-fit for the wave dataset considered. Long-term analysis is then performed on 38-years hindcast data for 10, 50 and 100 year return periods for the Mangaluru coast region. © 2020 National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.Item Prediction of wind-wave climate along Karnataka coast(Springer, 2021) Upadhyaya, K.S.; Rao, S.; Rao, M.Karnataka is a coastal state on the west coast of India along the Arabian Sea. The coast experiences a harsh wave climate during the southwest monsoons. Most of the coast is facing problems due to coastal erosion. Hence, in the present study, a numerical model has been set up using MIKE 21 Spectral Wave (SW) module to predict the wave climate. The wave climate along the Indian domain is simulated by wind speed datasets from Global Climate Model (GCM). Wind speed datasets from ERA-Interim is initially validated against in-situ measurement which had a correlation of 0.93. A hindcast study spanning 26 years based on 38 GCMs from different modelling institutes was performed. A comparison of wind speed datasets showed CMCC-CM RCP 4.5 wind projections were closer to ERA-Interim reanalyzed dataset and was used to predict the wave climate. The performance of the MIKE numerical model driven by CMCC-CM RCP 4.5 wind fields showed a correlation greater than 0.7 when validated against in-situ measurement. The numerical model simulations driven by wind speeds from CMCC-CM RCP 4.5 up to the year 2070 showed a gradual increase in the significant wave height which is indicative of the effects of climate change on the wave climate along the Karnataka coast. The projected significant wave height for 2070, when compared with the present wave climate, indicated an increase in the range of 10–21% at the six locations. The predicted wave pattern based on numerical simulations indicated a shift in the peak values in the monsoon month of June along the coast. The predicted wave parameters with a 10-year return period can be used for the design of coastal structures along the Karnataka coast. © 2021, Indian Academy of Sciences.