Faculty Publications

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Publications by NITK Faculty

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    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.
    2003
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    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.
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    Interfacial area and mass transfer coefficients in liquid-gas ejectors
    (2011) Arunagiri, A.; Iyyaswami, I.; Murugesan, T.
    Measurements and correlations are reported for the interfacial area and mass transfer coefficients as a function of energy dissipation in a liquid-gas ejector. The correlations for interfacial area and mass transfer coefficients have been developed using Kolmogorov's theory and Levich's hydrodynamic derivations. The present developed correlations are validated using experimental results. © 2011 Pleiades Publishing, Ltd.
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    An Energy-Efficient Hybrid Clustering Mechanism for Wireless Sensor Network
    (World Scientific Publishing Co. Pte Ltd wspc@wspc.com.sg, 2015) Muni Venkateswarlu, K.; Kandasamy, A.; Chandrasekaran, K.
    Valuable energy resources of sensor network should be utilized wisely to prolong network's lifetime. Clustering technique helps wireless sensor network (WSN) to enhance its lifetime by reducing energy consumption on every individual sensor node in the network. In multi-hop data forwarding model, difference in energy consumption among cluster heads (HS) causes hot-spot problem in the network. While data is being transferred, the CH close to base station are burdened with heavy relay traffic from several data routes and tend to die early. Unequal clustering avoids this hot-spot problem by establishing different sized clusters at various levels in the network. Since unequal clustering technique does not control number of CHs it creates, it forms huge number of clusters in the network. This increases hop count between source and destination, and leads to impose more over head on each data forwarding route in the network. Also, rapid variation in cluster size causes imbalance in energy dissipation among clustered nodes in the network. This uneven energy consumption influences network performance and lifetime. In this paper, we present an energy-efficient hybrid clustering mechanism for wireless sensor network using equal and unequal clustering techniques to create limited number of clusters in varied sizes at various level of the network. This avoids hot-spot problem with minimum hop count between the source and destination and achieves uniform energy dissipation between intra-and inter-cluster communication. Simulation results show that the proposed clustering mechanism balances the energy consumption among clusters with its hybrid cluster formation mechanism and elevates sensor network lifetime. © 2015 World Scientific Publishing Company.
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    Spatio-temporal probabilistic query generation model and sink attributes for energy-efficient wireless sensor networks
    (Institution of Engineering and Technology journals@theiet.org, 2016) Kumar, P.; Chaturvedi, A.
    Proliferation in Micro-Electro-Mechanical-Systems (MEMS) technology along with advancement in distributed computing infrastructure has facilitated the versatile usage and deployment of wireless sensors networks (WSNs) in last one and half decades. WSNs support large number of applications from the civilian and military regimes. Irrespective of these regimes; owing to difficulty associated with battery replenishment, proper energy usage has been at centre stage in WSNs operations. The lifetime of WSNs typically depends upon sensor's energy dissipation pattern, which is non-homogeneous with respect to spatial distribution over any short epochs. The genesis behind this nonhomogeneity is random generation of queries, which owes to application specific spatio-temporal parameters. Importance of spatio-temporal parameters is ubiquitous in WSNs paradigm and uncertainties are inevitable with these parameters, although the degree of uncertainties varies in accordance to applications served. Thus, from network design perspectives, precision involved with spatio-temporal aspects must be given due priority to obtain a mathematical model that maintains a good rapport with realistic query generation process. With these motivations, the study explores: (i) uses of energy-efficient clustering schemes, (ii) incorporation of spatio-temporal parameters uncertainties into probabilistic model of query generation using fuzzy-intervals bound, and (iii) sink attributes to enhance network lifetime. For various network surveillance scenarios; the performance measures average residual energy status and service-time-duration are estimated and analysed. © The Institution of Engineering and Technology 2016.
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    Magnetic field and frequency dependent LVE limit characterization of magnetorheological elastomer
    (Springer Verlag service@springer.de, 2017) Poojary, U.R.; Gangadharan, K.V.
    Magnetorheological elastomer (MRE) based semi-active isolators have the potential to replace conventional passive isolators to achieve wide frequency range isolation. The effectiveness of MRE isolator depends on the control strategies developed based on viscoelastic constitutive relations. The theory of linear viscoelasticity is the basis for viscoelastic constitutive relations which can predict the material behavior within a certain strain limit referred as linear viscoelastic (LVE) limit. Beyond the LVE limit, the performance of MRE semi-active isolator exacerbates as the control strategies turns out to be ineffective. In the present study, variation in LVE limit of MRE with the magnetic field and frequency is investigated through forced vibration tests. To exclude the effect of terminal non-linearity on the measurement, the blocked transfer stiffness method described in the ISO 10846-2 is adopted. The results revealed that the LVE limit of MRE is strongly dependant on the magnetic field and exhibited a weak dependency on the operating frequency. Under magnetized state, the transition from linear to non-linear behavior of MRE is at lower strain levels indicating the increased friction energy dissipation at particle–matrix interface. © 2016, The Brazilian Society of Mechanical Sciences and Engineering.
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    Study on performance of infilled wall in RC framed structure using basalt fibre in cement mortar
    (Structural Engineering Research Centre, 2019) Jagadeesan, P.; Palanisamy, T.
    Normally, Reinforced Concrete (RC) framed structure is built by combination of structural and non-structural elements that may satisfy the design and architectural purpose. When RC framed structures are subjected to the static lateral loading, infilled wall and RC frame elements does not react together. At this time, infilled wall is subjected only compressive forces and does not support the tensile force. So, failure is happened due to lacking of ductility and poor interaction between frame elements and infilled wall. Therefore, the objective of this study is to improve the ductility and interaction between RC frame elements and infilled wall through suitable method of strengthening of infilled wall. In this research work, the two types of specimens such as infilled RC framed structure and infilled RC framed structure strengthened by reinforced cement mortar using basalt fibre were cast and tested under experimental and analytical investigation. One-fifth scale model of single-bay, two-storey plane RC framed structure were prepared and tested under cyclic loading with the help of 1000 kN capacity loading frame and foundation block. This study focuses the significant parameters such as load-deflection curve, ductility, energy dissipation capacity, initial stiffness and failure mechanism of infilled RC frame and infilled RC frame with basalt fibre in cement mortar. The result proves that basalt fibre reinforced cement mortar improves the strength, stiffness and ductility of infilled RC framed structure and make infilled wall as integral unit in RC framed structure. © 2019 Structural Engineering Research Centre. All rights reserved.
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    Evaluation of a commercial MR damper for application in semi-active suspension
    (Springer Nature, 2019) Desai, R.M.; Jamadar, M.E.H.; Kumar, H.; Joladarashi, S.; Rajasekaran, S.C.; Amarnath, G.
    As the rheology of a magneto-rheological (MR) fluid can be controlled by an externally applied magnetic field, the damping force generated by a MR damper can be controlled by varying the current supplied to an electromagnet inside the damper. This paper presents the experimental evaluation of such a MR damper RD-8040-1 by Lord Corporation, USA, and its application in a semi-active suspension. The experiments were carried out in damping force testing machine. Sinusoidal displacement input was given to the test damper. The set of experiments were repeated for different levels of current (0–1.5 A in steps of 0.25 A) supplied to the MR damper. Plots of force versus displacement for each frequency of excitation and plots of maximum force versus frequency of excitation show that higher values of current lead to elevated values of MR damper forces. This increase in MR damper load with current supplied is studied and analyzed to develop a mathematical model of the MR damper under investigation. The nonlinear softening hysteretic behavior of the MR damper is simulated by using genetic algorithm provided in the optimization toolbox of MATLAB. Calculations on energy dissipation and equivalent damping coefficient of the MR damper show that the same damper can make the suspension system behave as an underdamped system, critically damped system or overdamped system depending on the value of current supplied to it. The application of this MR damper for heavy vehicle driver’s seat suspension is explored with the help of MATLAB simulations. © 2019, Springer Nature Switzerland AG.
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    Wave scattering by vertical porous block placed over flat and elevated seabed
    (Springer Science and Business Media Deutschland GmbH, 2019) Venkateswarlu, V.; Karmakar, D.
    The present study addresses the hydrodynamic characteristics of the incident wave through porous structure for both finite and shallow water depth. The oblique wave transformation due to the porous block over flat and elevated seabed and the submerged rigid block is presented. Analytical direct formulae are proposed to determine the wave reflection and transmission coefficient for the porous structure considering different configurations like porous block, porous block backed by wall, vertical wall away from the porous block and semi-infinite porous block at flat and elevated seabed. The analytical results for wave interaction with porous structure are presented considering the mode-coupling relation and eigenfunction expansion technique. Further, the significance of the semi-infinite porous block placed on the flat and elevated seabed is studied in detail. The analytical results obtained in the present study are validated with the numerical results available in the literature for specific cases. The significance of the critical angle and skin depth for the semi-infinite structure is explored in the wave structure interaction problems. The comparative study between various structural configurations suggests that, if the ratio of wavelength and width of the structure is greater or equal to unity (d/??1), then the structure can be regarded as semi-infinite porous block for flat and elevated seabed. The derived analytical formulae will be helpful in the preliminary design and analysis of the porous blocks. © 2019, Sociedade Brasileira de Engenharia Naval.
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    An experimental investigation on low-velocity impact response of novel jute/rubber flexible bio-composite
    (Elsevier Ltd, 2019) Mahesh, V.; Joladarashi, S.; Kulkarni, S.M.
    This paper presents an experimental investigation on low velocity impact (LVI) behaviour of flexible biocomposite laminates with different stacking sequence namely jute/rubber/jute (JRJ), jute/rubber/rubber/jute (JRRJ), jute/rubber/jute/rubber/jute (JRJRJ) and subjected to different impact energy levels using a conical shaped impactor. The performances of the proposed flexible composites are evaluated based on their energy absorption, peak force, coefficient of restitution (CoR), energy loss percentage (ELP) and failure behavior. Results indicated that JRJ provides better energy absorption and JRJRJ provides better damage resistance when subjected to LVI. Microscopic analysis revealed that the flexible composites fail mainly due to the tearing mechanism of the matrix as opposed to cracking in case of conventional stiff composites. It was also found that flexible composites are free from delamination. Compared to conventional stiff composites, there is no catastrophic failure observed in the proposed flexible composite. The overall performance evaluation of these proposed flexible composites indicates that these flexible composites can be potential sacrificial materials such as claddings used to protect primary structural components subjected to LVI. The systematic methodology employed in the present study serves as a benchmark for the effective utilization and selection of flexible composites for LVI applications. © 2019 Elsevier Ltd