Faculty Publications

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Author: search.filters.author.Nasar, T.

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    Coupled boundary element method (BEM) and finite element method (FEM) for hydroelastic analysis of floating plate
    (Springer, 2019) Shirkol, A.I.; Nasar, T.
    In the present study, a numerical model is developed to analyse equation of motion of the plate which is elastic in nature and has a shallow draft L/d ≤ 1/20 (small thickness). The platform may be of any shape (geometry) subjected to monochromatic waves. The developed numerical model is capable of investigating the VFLS of any geometry (arbitrary shape) at finite (0.05 ≤ h/λ ≤ 0.5) depth. A hybrid numerical model is developed and used to solve fluid–structure interaction between the elastic thin plate and water wave. A Higher Order Boundary Element Method (HOBEM) has been adopted in order to maintain the same order, basis function and contains the same nodes between BEM and FEM. Two equations have been determined to build the connection between plate displacement and velocity potential. Displacement of the floating platform has been obtained by solving the plate equation of motion. To solve the plate equation of motion, FEM has been adopted. The equation which relates the plate displacement and water is solved by Boundary Integral Equation (BIE). A modified Green’s function which differs from the bygone Green’s function has been developed by using the Bessel, Hankel and Struve functions of order zero. Both the equations are solved simultaneously to get the displacement of floating elastic plate and velocity potential. The results obtained are validated with Wang (J. Fluids Struct. 19:557–572, 2004 [22]). © Springer Nature Singapore Pte Ltd. 2019.
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    Experimental investigation on effect of submerged solid baffle in a barge carrying liquid sloshing tank
    (Springer, 2019) Nasar, T.; Sannasiraj, S.A.
    An experimental programme is conducted to investigate, barge responses, sloshing dynamics and sloshing pressure in a partially liquid-filled baffled tank which is equipped in a floating barge. The barge was subjected to regular wave excitations with wave height of 0.1m and frequencies ranging from 0.45 to 1.54Hz under beam sea condition. An aspect ratio (hs/l, liquid depth, hs to length of tank l) of 0.488 corresponds to 75% fill level is considered. In addition, a solid baffle wall at l/2 (height of solid baffle wall as h/2, h = tank height) is considered which is a typical arrangement in LNG sloshing tank. The effectiveness of solid baffle is investigated in comparison with unbaffled conditions. The barge responses at liquid-filled condition and equivalent dry weight conditions are compared. © Springer Nature Singapore Pte Ltd. 2019.
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    Geospatial and Hydrogeochemical Insights for Monitoring Water Quality and Salinity in Coastal Regions of Southern Karnataka, India
    (Springer Science+Business Media, 2025) Suryawanshi, V.; Ramesh, H.; Nasar, T.
    Coastal areas face significant challenges due to the depletion of groundwater and seawater intrusion into freshwater aquifers. Additionally, insufficient monitoring of freshwater quality is a major concern for consumers. In Karnataka’s Dakshina Kannada district, groundwater is crucial for meeting the needs of the community, industry, and agriculture. This study investigates the impact of excessive use, human activities, and agricultural chemicals on groundwater quality, with a focus on the hydrogeochemistry of the Natravathi and Gurapura catchments. The study analyzed 32 groundwater samples collected seasonally from 2021 to 2022 for 18 physiochemical parameters. The Water Quality Index (WQI) was determined using factors such as pH, Dissolved Solids, Oxidatio Reduction Potentisl, Electrical Conductivity, Total Hardness, Total Dissolved Solids, Calcium, Chlorides, Potassium, and Sodium. WQI scores ranged from 0 to 52 post-monsoon and 0 to 42 pre-monsoon. An ArcGIS-based spatial distribution map was created to show temporal changes in groundwater quality. Post monsoon measurements showed significant cations ranging from 4.25 to 64.54 mg/l, calcium from 40 to 520 mg/l, chloride from 40 to 200 mg/l, and potassium from − 8.05 to 15.44 mg/l. Pre-monsoon measurements indicated sodium levels from 28 to 208 mg/l, calcium from 240 to 840 mg/l, chloride from 19.99 to 159.9 mg/l, and potassium from 0 to 61.79 mg/l. WQI results for the post-monsoon season showed 36% of sampling sites as excellent, 52% good, 8% poor, and 4% very poor, while pre-monsoon results indicated 13% excellent, 46% good, and 42% poor. The research reveals higher toxin concentrations in drinking water during pre monsoon period compared to post monsoon, with increased salinity in freshwater aquifers making the water unsuitable for consumption. © 2025 The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    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.
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    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 Architects
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    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.
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    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 ASME
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    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.
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    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.
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    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.