1. Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/6
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Item Wave transmission and reflection for two rows of perforated hollow piles(2002) Rao, S.; Shirlal, K.G.; Rao, N.B.S.A laboratory investigation on perforated hollow piles in two rows was conducted in a two dimensional regular wave flume to study the wave transmission and reflection characteristics. The influence of incident wave steepness, relative clear spacing between the piles and rows of piles on transmission co-efficient and reflection co-efficient have been investigated. The effect of staggering of piles in the rows on both transmission and reflection co-efficients was also studied. The present study has revealed that for perforated pile groups incident wave steepness, relative clear spacing between the piles, relative clear spacing between the rows of piles influence both transmission and reflection co-efficients. Staggering of piles reduces reflection from the perforated piles. Perforated piles have smaller transmission and reflection co-efficient values compared to that of non-perforated piles at lower wave steepness.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 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 of berm breakwater with reduced armor stone weight(2004) Rao, S.; Pramod, Ch.; Rao, B.The basic principle involved in the design of S-shaped breakwater is the provision of a wide berm at or around the water level with smaller size armor stones than that used in conventional design, which are allowed to reshape till an equilibrium slope is achieved. An attempt is made to assess the influence of wave height, wave period, and berm width on the stability of S-shaped breakwater with reduced (30% reduction in armor stone weight) armor unit weight. From the investigation, it is found that the berm breakwater with 30% reduced armor weight would be stable for the design wave height if the berm width is 60 cm and wave period 1.2 s. For higher wave periods studied, zero damage wave height reduces by 20-40% of the design wave height. Wave period has large influence on the stability of berm breakwaters. The runup increases with decrease in weight up to Wo/W=0.9. 2004 Elsevier Ltd. All rights reserved.Item Stability of breakwater defenced by a seaward submerged reef(2006) Shirlal, K.G.; Rao, S.; Ganesh, V.; ManuThe stability of a uniformly sloped conventional rubble mound breakwater defenced by a seaward submerged reef is investigated using physical model studies. Regular waves of wide ranging heights and periods are used. Tests are carried out for different spacings between two rubble mound structures (X/d=2.5-13.33) and for different relative heights (h/d=0.625-0.833) and relative widths (B/d=0.25-1.33) of the reef. It is observed that a reef of width (B/d) of 0.6-0.75 constructed at a seaward distance (X/d) of 6.25-8.33 breaks all the incoming waves and dissipates energy and protects the breakwater optimally. 2005 Elsevier Ltd. All rights reserved.Item Stability aspects of nonreshaped berm breakwaters with reduced armor weight(2008) Rao, S.; Subrahmanya, K.; Rao, B.K.; Chandramohan, V.R.The present work involves the investigation of the influence of wave height, wave period, water depth, and sea-ward slope on the stability, wave runup, and wave rundown of statically stable rubble-mound berm breakwater. The weight of armor stones used in the present study is 20% lighter than the weight that is required for a conventional breakwater, designed using Hudson formula for a wave height of 0.1 m in the model. In the present work models with a berm width of 0.6 m, at constant depth of 0.32 m from the seabed were tested. The damage to the breakwater model with the berm was compared with the results on a model without the berm using different armor weights. The variation of relative runup and rundown was found for different values of wave steepness and water depths in front of the structure. The damage to the breakwater, wave runup, and rundown for the structure with seaward slope 1:2 and 1:1.5 were compared. The investigation was carried out in the Marine Structures Laboratory, Department of Applied Mechanics and Hydraulics, National Institute of Technology Karnataka, Surathkal. 2008 ASCE.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 Sediment trend matrix analysis along shore normal transects off Surathkal beach, Karnataka(2003) Rao, S.; Shirlal, K.G.; Rao, N.B.S.In order to study sediment travelling paths across shoreline in different seasons, sediment samples were collected normal to the shoreline along three profiles, separated by 220m from Surathkal beach near Karnataka Regional Engineering College (K.R.E.C.), Karnataka. The sediments were analysed for their grain size characteristics (statistical parameters) and sediment trend matrix was prepared. By using sediment trend matrix, sediment travelling paths were drawn. It has been found that during premonsoon, sediments were moving predominantly towards offshore region, resulting in erosion. Sediments were moving predominantly towards shore and build-up of beach takes place during the post monsoon season.
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