Journal Articles
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Item Item 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.(Wave transmission and reflection for two rows of perforated hollow piles) Rao, S.; Shirlal, K.G.; Rao, N.B.S.2002Item A laboratory investigation on a single row of suspended porous pipes is conducted in a two-dimensional wave flume to study their hydraulic performance under regular wave attack. The wave energy losses are computed and the effects of porosity, water depth, incident wave steepness and relative wave height on loss coefficient are studied. It is found that loss coefficient increases with an increase in incident wave steepness. Water depth has insignificant effect on K1 when wave steepness is varied. It is also observed that as porosity increases K1 decreases. For the range of variables studied, as the relative wave height increases, K1 decreases.(Energy dissipation in suspended porous pipe breakwaters in laboratory) Rao, S.; Rao, N.B.S.; Shirlal, K.G.2003Item 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.(Sediment trend matrix analysis along shore normal transects off Surathkal beach, Karnataka) Rao, S.; Shirlal, K.G.; Rao, N.B.S.2003Item A laboratory investigation on a single row of suspended porous pipes was conducted in a two-dimensional regular wave flume to study their hydraulic performance. The wave energy losses at the structure were computed and the effects of depth of submergence, incident wave steepness, water depth, pipe diameter, percentage of perforations, size of perforations and relative wave height on loss coefficient were studied. It was found that as incident wave steepness increases, loss coefficient K 1 increases. Water depth has insignificant effect on K 1. It is also observed that as percentage of perforations increases, K 1 increases. For the range of variables studied, as the relative wave height increases, K 1 decreases.(Energy dissipation at single row of suspended perforated pipe breakwaters) Rao, S.; Rao, N.B.S.; Shirlal, K.G.; Guddeti, G.R.2003Item Stability of breakwater defenced by a seaward submerged reef(2006) Shirlal, K.G.; Rao, S.; Ganesh, V.; Rao, M.The 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 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 Ocean wave transmission by submerged reef-A physical model study(2007) Shirlal, K.G.; Rao, S.; Rao, M.Ocean waves can be destructive as steeper waves due to their high energy eroding the sandy beaches. During storm surge or high tide, the water level rises and if large waves occur, they will break closer to the beach, releasing enormous amount of energy resulting in strong currents. This causes heavy loss of beach material due to large-scale erosion. If these waves are made to break prematurely and away from the beach, they can be attenuated so as to reduce beach erosion. The reef, which is a homogeneous pile of armour units without a core, breaks the steeper ocean waves, dissipates a major portion of their energy and transmits attenuated waves. This paper experimentally investigates the armour stone stability of the submerged reef and the influence of its varying distance from shore and crest width on ocean wave transmission. © 2007 Elsevier Ltd. All rights reserved.