Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
57 results
Search Results
Item A Review on Stability of Caisson Breakwater(Springer Nature, 2018) Gedda, A.B.; Rao, M.; Rao, S.A Breakwater can be designed for several different purposes; the basic function of such kind breakwater is to protect the water region against waves. It provides a tranquility condition for ships to navigate, moor, and for cargo handling. These vertical structures (caisson) are more economical compared to the rubble mound breakwater, especially in deeper water depths. There is a demand to expand existing ports or to make them more profound, to provide a sufficient tranquil harbor basin in deep-water due to increasing draught of large vessels. The material required for rubble mound breakwaters increase quadratic with depth, but the volume of the caisson is less than that needed for a rubble mound breakwater because the latter increases with the square of water depth. This paper concerned the previous design and failure mechanism on caisson breakwater and highlights the future studies for such kind of breakwater. © Springer Nature Singapore Pte Ltd. 2019.Item Prediction of damage level of inner conventional rubble mound breakwater of tandem breakwater using swarm intelligence-based neural network (PSO-ANN) approach(Springer Verlag service@springer.de, 2019) Kuntoji, G.; Rao, S.; Rao, M.; Reddy, E.N.B.The conventional rubble mound breakwater is a coastal protective structure commonly used decades before which alone failed to withstand the deepwater wave and its energy, and suffered a catastrophic failure. Keeping in mind both the safe functioning of harbor and stability of the breakwater for the fast-growing economy of the country, different types of breakwaters are being developed to serve this purpose. Tandem breakwater is an innovative type of breakwater, which is a combination of main conventional rubble mound breakwater and submerged reef in front of it. One of the advantages of this breakwater is that most of the wave energy is dissipated and wave intensity is reduced by submerged reef and the smaller waves interact with main breakwater and ensure its stability. Experimental studies are laborious and time-consuming to conduct. Therefore, it is necessary to carry out the detailed study of tandem breakwater stability by making use of simple and alternate techniques using the experimental data. In the present study, an attempt is made to understand the suitability and applicability of PSO-ANN, a hybrid soft computing technique for predicting damage level of conventional rubble mound breakwater of tandem breakwater. Based on the experimental data available in Marine Structure Laboratory, NITK, Surathkal, India, soft computing models are developed. The performances of the models are evaluated using model performance indicators. Results obtained demonstrate that the proposed new approach can be used to predict the damage level of conventional rubble mound breakwater of tandem breakwater efficiently and accurately. © Springer Nature Singapore Pte Ltd. 2019Item Swarm intelligence-based support vector machine (PSO-SVM) approach in the prediction of scour depth around the bridge pier(Springer Verlag service@springer.de, 2019) Marulasiddappa, B.M.; Rao, M.; Mandal, S.The mechanism of scour around the bridge pier is a complex phenomenon, and it is very difficult to make a common method to predict or estimate the depth of scour hole. In this paper, a hybrid model is developed, combining support vector machine and particle swarm optimization (PSO-SVM) to predict scour depth around a bridge pier. The input parameters such as sediment size (d50), the velocity of flow (U), and time (t) are used in the study to predict the scour depth. The models are developed with RBF, polynomial, and linear kernel functions, and the performances are evaluated using different statistical parameters such as CC, RMSE, NSE, and NMB. The predicted results are compared with measured scour depth. The predicted scour depth reveals that PSO-SVM with RBF kernel function model is found to be reliable and efficient in predicting the scour depth around bridge piers. © Springer Nature Singapore Pte Ltd. 2019Item Prediction of wave transmission over an outer submerged reef of tandem breakwater using RBF-based support vector regression technique(Springer, 2019) Kuntoji, G.; Rao, S.; Rao, M.The development of a mathematical model to determine transmitted wave height over a submerged reef of the tandem breakwater is complex. Therefore, it is necessary for researchers to adopt the physical model study to determine the parameters that influence the performance of breakwaters quantitatively. Physical modelling is laborious, expensive and lengthy in the procedure which makes it inconvenient for immediate needs. From the history, the development of the soft computing model shows that the soft computing techniques can be applied successfully to the prediction of the wave characteristics by making use of experimental data available. Similarly, attempt is made to predict the wave transmission over a submerged reef of tandem breakwater based on the data of Subba Rao developed in 2004 on a tandem breakwater in a 2D wave flume available at NITK Surathkal India using Support Vector Regression (SVR) model with different kernel functions. The non-dimensional input parameters used for the development of the models are five in number. Those inputs are incident wave steepness (Hi/gT2), relative reef crest width (B/Lo), relative reef submergence (F/Hi), relative reef crest height (h/d), depth parameter (d/gT2) and the output as (Ht/Htmax). The 202 data points (70%) are used for training and the 86 data points (30%) for testing out of 288 total data points. The statistical parameters are computed using the predicted and observed data points after training and testing the SVR models. The RBF kernel gives good correlation to the prediction of transmitted wave heights during testing with RMSE as 0.09 and MAE as 0.07. Therefore, the SVR with RBF kernel function can be adopted as an alternative technique to predict the wave characteristics such as wave transmission over a submerged reef of the tandem breakwater. © Springer Nature Singapore Pte Ltd. 2019.Item Offshore energy for the remote islands of lakshadweep(Springer, 2019) Srilakshmi, K.; Alluri, S.K.R.; Rao, M.Conjoining the available energy with renewable energy will allow us to utilize the renewable energy sector efficiently by reducing the current prices of electricity. Keeping this in mind, the island administration wants to shift towards renewable energy as the present diesel-electric system is posing a severe threat to its fragile environment of the island. Wind resource assessment was carried out and observed that wind energy has potential for energy generation. In the present paper, an attempt is made to study suitable substructure concepts along with detailed installation methodology for Lakshadweep. As these islands do not have the facility to handle more than 2 tons. It would be challenging to arrive at site-specific installation methodology for an offshore wind turbine. The aerodynamics loads are estimated by open source code ‘FAST’ and the hydrodynamic loads by Morison’s equation. These loads are transferred to structure and then to the soil, where its interaction is modelled as three nonlinear orthogonal springs. The behaviour of structure under combined loads is analysed using Finite Element Method. It is proposed to construct the gravity-based foundation onshore in lagoon side of the island, launched into the sea using hydraulic jacks, tow using tug and ballast at the proposed location. So, it is essential to identify the natural frequencies and Response Amplitude Operations (RAO) to understand the behaviour of foundation during towing. The draft of foundation is estimated under static condition and RAO’s are obtained using panel method. © Springer Nature Singapore Pte Ltd. 2019.Item Prediction of wave transmission characteristics at submerged reef breakwater(Elsevier Ltd, 2015) Sreeranga, S.; Shirlalb, K.G.; Rao, M.Submerged reef breakwater is an off shore breakwater, with its crest at or below the sea water level, used for protection of coastal structures and beaches from the erosion caused by wave action. Reef breakwaters are coast parallel structure built wi th an objective of reducing the wave action on the beach. It is constructed with uniformed size armour whose weight is sufficient to resist wave attack. Modeling of co-efficient of wave transmission (Kt) of such reef is a topic chosen for present study. Preliminary equation is derived from dimensional analysis as semi empirical equation which involves different parameters like wave characteristics, reef dimensions and nominal diameter of armour units. Simulation of results is undertaken with modeling in MATLAB. Results obtained are thus compared with experimental results and existing equations from the literature. Finally semi-empirical equation for Kt is established. © 2015 Published by Elsevier Ltd.Item PSO-SVM approach in the prediction of scour depth around different shapes of bridge pier in live bed scour condition(Springer Verlag service@springer.de, 2019) Marulasiddappa, B.M.; Kuntoji, G.; Rao, M.; Mandal, S.Scour is one of the major factors which affects directly on the durability and safety of the Bridge abutments. Based on the experimental data of Goswami in 2012, an effort is made to predict local scour by using a hybrid approach of Swarm Intelligence based algorithms which is today one of the powerful tools of optimization techniques. In this work, an intelligent model based on support vector machine in combination with the particle swarm optimization (PSO-SVM) technique is developed. The PSO-SVM models are developed with RBF, Polynomial and Linear kernel functions. The circular, rectangular, round-nosed, and sharp-nosed shapes of piers are considered in live bed scour condition. The scour depth around bridge piers is predicted by considering Sediment size, flow velocity, and time of flow as input parameters. Prediction accuracy of the models is evaluated using the model performance indicators such as Root Mean Square Error (RMSE, Correlation Coefficient (CC), Nash Succlift Error (NSE), etc. The results obtained from the model are compared with the measured scour depth to validate the reliability of the hybrid model. Based on the results, PSO based SVM model is found to be successful, reliable, and efficient in predicting the scour depth around the bridge pier. © Springer Nature Singapore Pte Ltd. 2019.Item Experimental investigations of structurally pre-stressed actuator based active vibration isolation system(American Institute of Physics Inc. subs@aip.org, 2020) Divijesh, P.; Rao, M.; Rao, R.; Dheeraj; SushithActive Vibration Isolation is considered to be one of the most effective methods to reduce the undesirable vibrations generated in any mechanical system. Stacked piezoactuators are suitable actuators used for variety of applications such as micro and nano positioning applications because of their high stiffness and fast response. However in order to provide optimal preloading force to the stacked actuators for longer lifetime and better performance with dynamic applications these stack actuators are structurally pre-stressed. In the present work, an active vibration isolation system is designed and developed using two structurally pre-stressed actuators namely source actuator and isolator actuator where source actuator is used for generating vibrations and the isolator actuator to nullify the generated vibrations. Initially the transfer function of the MLA 10x10x20 stack actuator was identified using its known parameters and was modeled in MATLAB/ Simulink to estimate the simulated displacement for a particular voltage at different frequencies. The simulated displacements were then compared with experimental displacements for different frequencies and the results were plotted. The experimental displacements of both source actuator and isolator actuator were found at different frequencies and was compared with the simulated displacements for a particular voltage and the results were plotted. Finally active vibration isolation experiments were carried out using the proposed set up for a particular voltage at different frequencies and the percentage of vibration isolation achieved was also estimated. © 2020 Author(s).Item An experimental investigation on toe stability for vertical—caisson breakwaters(Springer Science and Business Media Deutschland GmbH, 2021) Kumaran, V.; Subba Rao; Rao, M.For the design and construction of a vertical-caisson breakwater which is more significant task in the field of ocean engineering, since the incidicent wave and reflected wave acting on the structure causes severe bottom scouring and final leads to failure of the structure. The influences of wave height, wave period, and toe armor unit stability are under investigation in this study. The experimental work conducted by Brebner and Donnelly [1], was put forward, that for a certain fixed relative foundation depth (d1/d) and wavelength (L), the significant wave height (Hs), will have an exponential relationship with the number of rocks displaced in the armor layer of the toe of the vertical-caisson structure. The investigation are conducted in the regular 2D wave flume at wave mechanics laboratory, NITK, Surathkal. The present paper provides the required information regarding the damage level of toe armor units in transition water depths and the effect of wave parameters are analyzed. © Springer Nature Singapore Pte Ltd 2021.Item Development of piezoactuator based rotary tool feeding system for micro-EDM(Elsevier Ltd, 2022) Venugopal, T.R.; Rao, M.; Rao, R.; Sushith, K.Micro Electrical Discharge Machining (micro-EDM) is widely employed for the fabrication of component parts used in Micro Electro Mechanical System (MEMS) devices and many other applications. Spark gap, being a critical process parameter in micro-EDM, must be maintained at optimum length for stable machining. To meet this critical requirement, the tool feeding system employed in micro-EDM must be capable of feeding the tool electrode adaptively to maintain the optimum spark gap. This paper proposes to develop a Flexurally Amplified Piezoactuator based rotary tool feeding system for micro-EDM. Hysteresis behavior of the piezoactuated tool feeding system is modeled using Maxwell's hysteresis model. Model based tool feed control experiments were conducted for different feed displacements ranging from 100 μm to 600 μm and spindle rotational speeds from 400 rpm to 1800 rpm. From the experimental results it is observed that the developed rotary tool feeding system performs with an error less than 1% for larger feed displacements at higher spindle speeds. Machining experiment with tool rotation enhanced blind hole depth by 29.21% compared to machining without tool rotation. [copyright information to be updated in production process]. © 2022 Elsevier Ltd. All rights reserved.