1. Journal Articles
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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 Wave runup, rundown and stability analysis on berm breakwater with 20% reduced armour weight(2005) Rao, S.; Subrahmanya, K.; Rao, K.B.; Chandramohan, V.R.This paper presents the results of the experimental investigation of the stability, wave runup and rundown characteristics of the statically stable berm breakwater with a wide berm. Armour weight calculated using Hudson's formula for design wave height has been reduced to an extent of 20% in the present study. The variations of non-dimensional runup values (Rd/Ho) and the rundown values (Rd/Ho) with deep- water wave steepness (Ho/gT2), damage level (S) with stability number (Ns) are investigated for different depths of still water level (SWL). A decrease in runup and rundown with wave steepness has been observed. Location of berm near SWL has been found to be more effective in reducing the wave runup. Damage level increases with decrease in wave period within the limits of experimental variables studied. � 2005 Taylor & Francis Group, LLC.Item Wave Reflection and Loss Characteristics of an Emerged Quarter Circle Breakwater with Varying Seaside Perforations(2017) Binumol, S.; Rao, S.; Hegde, A.V.Breakwaters are one of the most important harbour structures constructed to withstand and dissipate the dynamic energy due to the action of the waves. Due to fast growing need of the universe and advances in technology different types of breakwaters are being developed. Quarter circle breakwater is a new type of breakwater emerged from semi circular breakwater and the first model was developed in Peoples Republic of China (2006). Quarter circle breakwater with perforations posses merits of caisson as well as perforated breakwaters such as low weight, requires less materials, suited for poor soil conditions, easily transported, handled and placed at the site, aesthetically pleasing, cost effective, eco-friendly and stable. Therefore it is necessary to carry out detailed studies on hydrodynamic characteristics to investigate the suitability and applicability of various types of quarter circle breakwaters. The present study investigates the wave reflection and loss characteristics of an emerged seaside perforated quarter circle breakwater of radius 55�cm and with varying ratios of spacing to diameter of perforations, for different water depths and wave conditions. The tests were conducted in the two-dimensional monochromatic wave flume available in Marine Structures laboratory of Department of Applied Mechanics and Hydraulics of National Institute of Technology, Surathkal, Karnataka, India. The results were plotted as non-dimensional graphs and it was observed that the reflection coefficient increases with increase in wave steepness for all values of ratio of height of breakwater structure to water depth. For a constant water depth, wave reflection increases with increase in ratio of spacing to diameter of perforations. It was also found that the loss coefficient decreases with increase in wave steepness for all values of ratio of height of breakwater structure to water depth, and ratio of spacing to diameter of perforations. � 2017, The Institution of Engineers (India).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.; Vittal, Hegde, A.; 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 Stability of tandem breakwater(2003) Shirlal, K.G.; Rao, S.; Prasad, S.K.M.The concept of rubble mound breakwater and submerged reef breakwaters, operating together as a single unit, is called the tandem breakwater. The effect of the submerged reef breakwater on the stability of non-overtopping rubble mound breakwater on its leeside was investigated in the present study, The tandem breakwater was tested for two spacings between the breakwaters, ie,for 1 m and 2,5 m. For each of the spacing, the effect of water depth, wave-period and wave height on the stability of tandem breakwater was studied. In the present study, the damage level of tandem breakwater for a relative spacing varying from 2.22 to 7.14 was 10% to 40% less compared to that of a single breakwater designed to meet the same operating criteria.Item Stability equation for breakwater sheltered by a seaward submerged reef(2007) Shirlal, K.G.; Rao, S.; Manu, M.Breakwater's vulnerability to extreme events such as storms is a reality. To avert the failure of the breakwater, one of the things engineers can do is to design a seaward reef which breaks steep waves and attenuates them. The stability of such a reef, a conventional rubble mound breakwater and a breakwater protected by a seaward submerged reef is investigated through physical model study using regular waves. Tests are carried out for different relative spacings between two rubble mound structures (X/d = 2.5 to 13.33) and for different relative heights (h/d = 0.625 to 0.833) while keeping reef crest width B constant at 0.1m (i.e. the relative crest width B/d = 0.25 to 0.33). The submerged reef of crest width 0.1m located at a seaward distance X of 1 m, 2.5 m and 4.0 m reduces the breakwater damages by a range of 4 to 41 %, 40 to 66% and 63 to 80% respectively. The stability equations for reef and defenced breakwater are derived from curve fitting through the experimental data. 2007 Taylor & Francis Group, LLC.Item Study of coastal erosion along karnataka coast(2002) Rao, S.In the recent years, it is quite common that with the onset of monsoon, a lot of hue and cry is raised by the people who are living along the coast line about erosion and damage to property. In order to monitor the actual extent of this problem along the Karnataka coast and to find the causes of erosion, a detailed analysis of the available data and field study of beach profiles were taken up. From the detailed study, it can be concluded that there are significant natural changes that occur in river mouths in Karnataka coast. This assumes serious proportions when these areas are encroached by population. Coastal erosion, if any on Karnataka coast, is due to direct wave action. In certain stretches, there is concentration of wave energy due to refraction and these areas are more vulnerable to erosion. Beaches adjacent to coast parallel rivers are also more vulnerable to erosion due to higher water tables that exist when the rivers flow full in monsoon. Littoral drift and sea level changes do not pose any problems in Karnataka coast. 2002 Taylor & Francis Group, LLC.Item Performance of single row of suspended porous pipe breakwater(2001) Rao, S.; Rao, N.B.S.; Reddy, Y.V.B.A laboratory investigation on single row suspended porous pipes was conducted in a two-dimensional regular wave flume to study their hydraulic performance. The effects of porosity, water depth, incident wave steepness and relative wave height on transmission and reflection coefficients were studied. It was found that (a) as incident wave steepness increases transmission coefficient Kt decreases and reflection coefficient Kt increases; (b) water depth has insignificant effect on Kt and Kt for porous pipes; (c) as porosity decreases Kt decreases and Kt increases; and (d) the range of variables studied, as the relative wave height increases Kt increases and Kr decreases.Item Performance evaluation of ANFIS and SVM model in prediction of wave transmission over submerged reef of tandem breakwater(2017) Kuntoji, G.S.; Rao, S.; Manu; Mandal, S.Tandem breakwater plays a unique role in protecting the ports. It is an innovative breakwater concept consisting of conventional breakwater and a submerged reef operating in tandem. As the depth-limiting behaviour of reef, the tandem possesses less design risk for extreme events. For a tandem breakwater, the transmitted wave over the submerged reef plays avital role in the safety of the emergent breakwater. Coastal structures like breakwaters are massive in terms of size as well as in the costs. Any structure before finally being constructed has to be subjected to model investigations for its safety against the design parameters. The soft computing techniques such as ANFIS (Adaptive Neuro Fuzzy Inference system) and SVM (Support Vector Machine)models are developed using experimental data points to predict the hydraulic performance of submerged reef of tandem breakwater. The performances of two models are validated with measured data, with the help of statistical measures namelyRMSE (Root MeanSquare-Error), CC (CorrelationCo-efficient), SI (Scatter-Index) andNSE (Nash-Sutcliff Efficiency). The results testify that SVM model performed better with 0.965 CC, 0.0557 RMSE, 0.9113 NSE and 0.1503 SI compared to ANFIS model with 0.935 CC, 0.0754 RMSE, 0.869 NSE and 0.00233 SI. 2017 by International Journal of Ecology & Development.Item Seawalls: Performance and their failure analysis along Southern Karnataka, West Coast of India(2012) Rao, S.; Hegde, A.V.; Dwarakish, G.S.; Prashanth, J.; Reddy, D.V.Beach erosion is a major problem along the south west coast of India. The beach erosion particularly along the south Karnataka coast is due to, 1) direct attack of waves in an open coast, which might have been intensified in some areas due to wave refraction, 2) erosion at river mouths where one or two rivers together join the sea. The coastal protection works adopted along the South Karnataka coast are mainly the seawalls. However, some portions of these seawalls have been damaged either partially or fully. A critical study shows that these failures are due to the scouring at the toe structure. Scouring causes the failure of the seawall due to loss of support. A calculated risk may be taken to design the seawall without taking scour depth into account but provide for adequate maintenance in case scour occurs and partial failure of the seawall takes place. 2012 Cafet-Innova Technical Society. All rights reserved.