Conference Papers
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Item PID control of structure with tuned liquid column damper(Institute of Electrical and Electronics Engineers Inc., 2016) Abubaker, S.; Nagan, S.; Nasar, T.New civil engineering structures are long and slender and they have less damping. Therefore they are subjected to large vibrations when earthquake or wind acts. These excitations may cause structural collapse of the structure. Therefore to control these vibrations supplementary control devices are used. Tuned liquid column damper (TLCD) is one of a passive control device to reduce the excitations. TLCD will transfer the energy from the structure to TLCD by the motion of water in a U-shape tube like devices fitted with an orifice opening. Due to this motion the excitations will reduced. The aim of this paper is to study the effectiveness of PID control in TLCD system. The results are obtained with structure only, passive, PID controlled system. From this paper, the vibrations can be effectively suppressed with the PID controller. © 2016 IEEE.Item Scale effects of sloshing on a sway excited rectangular ship tank(Royal Institution of Naval Architects membership@rina.org.uk 10 Upper Belgrave Street London SW1X 8BQ, 2019) Shri, S.; Nasar, T.Sloshing behavior of liquid in containers is one of the fundamental fluid-structure interactions. Liquid sloshing is associated with various dynamical systems and engineering problem, such as the liquid cargo slosh in ships and trucks of transporting liquid, oil oscillation in large tanks, and water oscillation in a reservoir due to ground and wind acceleration, etc. Oscillation of water in a partially filled container due to the external forces or external disturbances is called as sloshing. An experimental study has been carried out to study the scale effects on sloshing dynamics of liquid in a partially filled sway excited rectangular tank. The model tanks considered in this study are 1:43, 1:57 and 1:86. The aspect ratio (hs/L) of 0.1625, 0.325, 0.4875 are adopted which represents 25%, 50% and 75% of liquid fill levels of tank depth respectively. A sloshing tank is positioned on the shake table such that during the sway excitations, the sloshing oscillations occurs along the longitudinal axis. Time histories of sloshing oscillations and sloshing force are measured using load cells and wave probes, respectively. The effect of excitation frequencies and excitation amplitudes on sloshing force and sloshing oscillations is discussed here. © 2019: The Royal Institution of Naval ArchitectsItem A study on shore-line dynamics during and post-construction of breakwaters in kasaragod fishing harbour(Springer Science and Business Media Deutschland GmbH, 2021) Chaitanya, V.K.; Nasar, T.; Paravath, K.Coast belonging to one particular stretch happens to be versatile because of its dynamicity. This dynamicity is accounted because of both natural and man-made activities. Hence, it is necessary to monitor any fragile coastal stretch’s dynamicity in a temporal basis. In this study, an attempt is made to study the dynamicity of coastal morphology using geospatial and numerical approach. Shore-line on both sides of Kasaragod River firth, laterally Karnataka coast of the India, has modified following construction of breakwaters for fishing harbour. The breakwaters were constructed between 2010 and 2015 after which a severe change is observed in shore-line. Construction flaws were reported as a result of which strong waves were formed leading to the difficulty in launching boats into the sea. Coastal morphology needs to be further analysed to propose a more scientific and lasting solution. Shore-line is extracted from field surveyed data (supplied by Department of Harbour Engineering, Kerala). To ensure the forecast end point rate (EPR) and linear regression rate (LRR) for shore-line data, digital shore-line analysis (DSAS) technique was applied and compiled for up to 2017 in response to the construction of a pair of breakwaters at river inlet. © Springer Nature Singapore Pte Ltd 2021.Item Drag coefficient for porous screen in a non-oscillating perpendicular to plane-in flow(American Society of Mechanical Engineers (ASME), 2021) Bhandiwad, M.S.; Nasar, T.The flow-through porous bodies/structure is one of the more advanced research in the area of energy dissipation in coastal and civil engineering fields. The experiments on the determination of drag coefficient of screens with varying porosities and for the range of flow velocities lead to explore damping ratio in a typical fluid-structure interaction problem. An experimental study has been carried out to assess the drag coefficient of the porous screens as suggested by Keulegan, G. H (1968) [3]. Six different screens with porosities of 4.4%, 6.8%, 9.2% 15%, 20% and 25% are considered. In the experiments, water with a known head from one tank is allowed to flow through a pipe equipped with porous screens into the other tank. Based on the experimental observation, the correlation between Reynolds number and drag coefficient is obtained for all porous screens. The effect of damping nature (damping ratio) of the screen for a particular range of Reynolds number has been explored. As the Reynolds number increases, the drag coefficient decreases with increasing the porosity of the screen. Further, it is understood that the value of the damping ratio decreases with an increasing relative head (H/L). © © 2021 by ASMEItem Impact of Estuarine Breakwaters on Adjacent Shorelines at Muthalapozhy Harbour in Kerala(Institute of Electrical and Electronics Engineers Inc., 2022) Paravath, K.; Nasar, T.A shoreline is a boundary between the land and the ocean, is prone to periodic changes on account of various dynamic factors such as wave characteristics, coastal orientation, currents, and bathymetry. As a result, shoreline location varies continuously with respect to time. Shoreline change is the direct consequence of coastal erosion and accretion, along with the effect of nearshore currents. Shorelines on both sides of Muthalapozhy tidal inlet, which is located along Kerala coast in India, was modified following the construction of breakwaters for developing a fishery harbour. The fishing harbour work was initiated in 2002. Severe erosion at the immediate north of the north breakwater and choking of harbour mouth due to spit formation was observed. The construction of modified breakwaters began in 2013, after resolving the deficiencies in the first phase. An attempt to study the shoreline oscillations at Muthalapozhy harbour using numerical approach is reported in this paper © 2022 IEEE.Item A Study on Morphodynamic Nature of Muthalapozhi Fishery Harbour in Kerala Using Geospatial Approach(Springer Science and Business Media Deutschland GmbH, 2023) Paravath, K.; John, A.; Nasar, T.It is crucial to monitor the dynamics of any fragile coastal stretch on a regular basis. Shorelines on both sides of Muthalapozhi tidal inlet, which is located along Kerala coast in India, were modified after the construction of breakwaters for a fishing harbour. The fishing harbour work was initiated in 2002. Severe erosion at the immediate North of the breakwater and choking of harbour mouth due to spit formation was observed. The construction of modified breakwaters began in 2013, after resolving the deficiencies in the first phase. Coastal morphology needs to be further analysed to check the adequacy of the breakwaters. An attempt to study the dynamicity of coastal morphology of Muthalapozhi Harbour using geospatial approach is reported in this paper. In response to the breakwater construction, End Point Rate (EPR) and Linear Regression Rate (LRR) are calculated using Digital Shoreline Analysis System (DSAS) in ArcGIS software. The results indicate that high accretion with a maximum rate of 209 m/year in the year 2019 is observed on the immediate southern side of the south breakwater. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Groundwater Quality Evaluation In The Gurupura River Basin Using GIS and Remote Sensing Approach(Institute of Electrical and Electronics Engineers Inc., 2023) Suryawanshi, V.; Ramesh, H.; Nasar, T.The objective of this study was to assess the quality of groundwater resources in the Gurupura basin, located in Dakshina Kannada district, Karnataka, India, specifically for domestic and drinking purposes. To achieve this, various water quality analysis techniques were employed, such as the water quality index (Brown's 1970), spatial groundwater evaluation using GIS-based interpolation, and multivariate statistical analysis. Physiochemical parameters of groundwater samples were analyzed on-site both before and after the monsoon season of 2021. The findings of the study indicate that the groundwater quality deteriorates during the pre-monsoon period, primarily due to a decline in the groundwater table and the presence of salinity in coastal wells. However, in the post-monsoon period, the groundwater quality significantly improves and is deemed pure and suitable for both drinking and domestic purposes. © 2023 IEEE.Item Effectiveness of porous baffle on resonance sloshing motion: An experimental study(American Institute of Physics Inc., 2023) Sahaj, K.V.; Nasar, T.Liquid movement in tanks that is partially filled can cause large structural loads if the tank movement is near the natural period of fluid within the tank. Sloshing implies the movement of a free liquid surface inside a vessel. A shake-Table experiment for various depths of water of aspect ratio 0.163, 0.325, and 0.488 are investigated to examine the effect of sloshing. The frequencies of excitation range from 0.4566 Hz to 1.9757 Hz which covers up to the fifth mode sloshing frequency and a constant amplitude of 7.5mm is adopted. A single porous at l/2 location is considered to check its effectiveness in comparison with the unbaffled condition. Three different porosities of 15%, 20%, and 25 % are adopted. Capacitance wave probes are used to record the free surface elevation at the end walls. The results of maximum free surface elevation (ηmax) and spectral moments (mo) are present here. The suppression of resonant sloshing motion by porous baffle is analyzed. A higher sloshing oscillation is observed for the aspect ratio (hs/l) of 0.325 than compared with the other two fill levels. © 2023 Author(s).Item Integrated Ecological River Health Assessment of Netravathi Basin Based on Physiochemical and Hydrochemical Analysis(Springer Science and Business Media Deutschland GmbH, 2024) Suryawanshi, V.; Ramesh, H.; Nasar, T.River health assessment is critical, and it is essential to monitor the river's quality and health condition. Because most rivers are drying up and becoming polluted as a result of a lack of assessment and regular maintenance, all major elements of a riverine system, such as aquatic flora and fauna, water quality, habitat, hydrology, the physical shape of the channel, and other geomorphological elements, should be considered and included in it. The objective of this research is to assess the health of the Netravathi River using physiochemical parameters. River Netravathi is the only freshwater resource in Mangalore's coastal metropolis. The river flows 103 km from its point of origin to Mangalore city, with catchment area of 3657 Km2. To assess river health, seven physical parameters were measured seasonally at the river site, and laboratory testing of river water samples for eight chemical parameters have been carried out. Rivers are essential to the life and survival of many plant and animal species. The discharge of sewage, industrial effluents, municipal solid waste, agricultural waste all of which impact the water quality carried by river flow. According to the findings, the health of the River Netravathi is considerably better in the post-monsoon season than in the pre-monsoon season, because the river becomes dry in most sections of the district and the flow of river water drops dramatically. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Experimental Study on Liquid Sloshing Dynamics in a Sway Excited Rectangular Tank(Springer Science and Business Media Deutschland GmbH, 2024) Sahaj, K.V.; Shri, S.; Nasar, T.An experimental shake table program is performed to explore the hydrodynamic behavior of liquid sloshing phenomena in a partially filled rectangular tank of 1:43 scaled tank subjected to sway excitation. Three different aspect ratios (hs/l, liquid depth, hs to the length of the tank, l) of 0.163, 0.325 and 0.488 which corresponds to 25%, 50% and 75% fill depths are considered. Excitation parameters such as frequencies ranging from 0.45 to 3.2 Hz which encompasses up to fifth mode of sloshing frequency and amplitudes of 4 and 8 mm are considered. An experimental setup is designed and devised to measure the sloshing force by using ballast mass concept. The experimental parameters such as run-up of sloshing oscillation, sloshing force and spectral energy are discussed. Experimental results of sloshing oscillation are compared with the numerical works of Nasar et al. (J Nav Archit Mar Eng 9:43–65, 2012). The present study reveals that the effect of excitation on sloshing oscillation is more pronounced near first mode of resonance and insignificant at off-resonance conditions. The effect of excitation amplitude on the fill level is pronounced in the order of 50, 25 and 75% fill levels on sloshing oscillation, sloshing force and spectral energy. The sloshing force is found to be about 9.32, 26.03 and 26.43 N for the excitation parameters of forcing frequency (f) that equals to first mode sloshing frequency (f1) and amplitude of excitation A = 8 mm. The sloshing tank with 75% fill depth experiences more sloshing force on its containment than 25 and 50% fill depths. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.