Faculty Publications
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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 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.(Wave runup, rundown and stability analysis on berm breakwater with 20% reduced armour weight) Rao, S.; Subrahmanya, K.; Balakrishna Rao, K.B.; Chandramohan, V.R.2005Item Physical model studies on wave transmission of a submerged inclined plate breakwater(2009) Rao, S.; Shirlal, K.G.; Varghese, R.V.; Govindaraja, K.R.This paper examines the results of physical model studies conducted in a monochromatic wave flume, to evaluate the wave transmission characteristics of a submerged plate breakwater consisting of a fixed plate of 0.50 m length and 0.003 m thickness. The model was oriented at varying inclinations and submergence. The influence of wave steepness, relative depth, relative submergence and angle of inclination on wave transmission was analysed. It was found that the horizontal plate is effective for short waves with steepness parameter higher than 5×10-3 in relative depth grater than 0.21. The plate oriented at an angle of inclination of 60° is found to be effective for the entire ranges of wave parameters considered for the study and it reduces the wave height by about 40%. © 2009 Elsevier Ltd. All rights reserved.Item Peak mooring forces in the horizontal interlaced multi-layered moored floating pipe breakwater(Society of Naval Architects of Korea, 2011) Mane, V.; Rajappa, S.; Rao, S.; Hegde, A.V.Present study aims to investigate the influence of relative breakwater width W/L (W=width of breakwater, L=wavelength), wave steepness Hi/gT2 (Hi=incident wave height, T=wave period) and relative wave height d/W (d=water depth) on forces in the moorings of horizontal interlaced multi-layered moored floating pipe breakwater (HIMMFPB) model. Studies were conducted on scaled down physical models having three layers of Poly Vinyl Chloride (PVC) pipes, wave steepness Hi/gT2 varying from 0.063 to 0.849, relative width W/L varying from 0.4 to 2.65 and relative spacing S/D=2 (S=horizontal centre-to-centre spacing of pipes, D=diameter of pipes). Peak mooring forces were also measured and data collected is analyzed by plotting non-dimensional graphs depicting variation of fs/?W2 (fs=Sea side Mooring force, ?=specific weight of water) & fl/?W2 (fl=Lee side Mooring force) with Hi/gT2 for d/W varying from 0.082 to 0.276 and also variation of fs/?W2 and fl/?W2 with W/L for Hi/d varying from 0.06 to 0.400. © SNAK, 2011.Item Concrete cubes as armour unit—an experimental study for berm breakwater(2011) Shirlal, K.G.; Rao, S.; Madhu, M.Berm breakwater consists of a wide berm at or around the water level and has an armour layer, whose shape changes in response to wave action yielding a stable profile. In the present study the influence of wave height, wave period and berm width on the stability of the breakwater as well as on the wave runup and wave rundown are studied. Experiments were conducted on berm breakwater model of 1:30 scale using concrete cubes as armour units. For the given experimental conditions the stability number was found to vary from 2.21 to 3.63. Further the model in 0.37m water depth was more stable than the one in 0.40 and 0.43m. The runup values were within the range of 0.52 to 1.08. While, the rundown values had the variation from 0.45 to 0.88. © 2011 Taylor & Francis Group, LLC.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 Run-up, run-down and reflection characteristics of semicircular breakwater for varying seaside perforations(2012) Hegde, A.V.; Rao, S.; Kumar, K.Breakwaters are mainly used for the purpose of withstanding and dissipating the dynamic energy of ocean waves and thereby provide tranquillity conditions on the lee side. Semicircular breakwaters are being used increasingly around the globe because of their great advantages. The paper explains physical studies conducted on seaside-perforated semicircular breakwater models to evaluate the wave run-up, wave run-down, and reflection coefficient for various wave heights (H), wave periods (T), water depths (d), incident wave steepness (H i/gT 2), depth parameter (d/gT 2), and relative spacing S/D (S = c/c spacing of perforations, D = diameter of perforations) on the seaside. It is observed that as the incident wave steepness increases, there is a decrease in the reflection coefficient (K r), and relative run-down (R d/H i) but increase in relative run-up (R u/H i). As the S/D ratio decreased (percentage of perforations increased), there was drop in the reflection coefficient, relative run-up, and relative run-down. As the depth parameter increased, there was a decrease in the relative run-up and reflection coefficient, but increase in relative run-down. © 2012 Taylor & Francis Group, LLC.Item Wave Reflection and Loss Characteristics of an Emerged Quarter Circle Breakwater with Varying Seaside Perforations(Springer India sanjiv.goswami@springer.co.in, 2017) Shahulhameed, 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 Multiple Nonlinear Regression Analysis for the Stability of Non-overtopping Perforated Quarter Circle Breakwater(Editorial Board of Journal of Harbin Engineering, 2020) Shahulhameed, S.; Rao, S.; Hegde, A.V.Breakwaters have been built throughout the centuries for the coastal protection and the port development, but changes occurred in their layout and criteria used for the design. Quarter circle breakwater (QBW) is a new type evolved having advantages of both caisson type and perforated type breakwaters. The present study extracts the effect of change in the percentage of perforations on the stable conditions of seaside perforated QBW by using various physical models. The results were graphically analyzed using dimensionless parameters and it was concluded that there is a reduction in dimensionless stability parameter with an increase in steepness of the wave and change in water depth to the height of breakwater structure. Multiple non–linear regression analysis was done and the equation for the best fit curve with a higher regression coefficient was obtained by using Excel statistical software—XLSTAT. © 2020, Harbin Engineering University and Springer-Verlag GmbH Germany, part of Springer Nature.