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Surendran Sankunny
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Surendran Sankunny
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Surendran Sankunny
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Surendran, S.
Sankunny, Surendran
Surendran, Sankunny
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16 results
Now showing 1 - 10 of 16
- PublicationStudies on an algorithm to control the roll motion using active fins(01-03-2007)
; ;Lee, S. K.Kim, S. Y.The very purpose of attaching fins to the hull is to reduce the roll motions of a ship. Roll minimization is a requisite for various operations in the seas. The presence of fin system provides enhanced state of stabilization especially when the vessel is performing a fast maneuvering amidst rough environmental disturbance. The fins in turn are activated by electro-hydraulic mechanism based on the in-built intelligence as per control theory like proportional-integral-derivative (PID) or fuzzy logic. As per this paper, fin system is activated using PID control algorithm. A frigate-type warship is considered for the demonstration purpose. Nonlinear roll motions are controlled using active fins. Lift characteristics of the fins in hydrodynamic flow were studied using CFD package fluent. Good amount of reduction in roll amplitude is achieved from various simulations in random sea. The approach can be used for any irregular sea conditions. © 2006 Elsevier Ltd. All rights reserved. - PublicationRoll dynamics of a Ro-Ro ship(01-12-2002)
; Venkata Ramana Reddy, J.The prediction of ship stability during the early stages of design is very important from the point of safety. Ships experience six modes of rigid body motions in a seaway, which can be split into two groups as translatory and oscillatory motions. Out of the six motions of a ship, the critical motion leading to capsize of a vessel is the rolling. In the present study, particular attention is paid to the performance of a ship in beam sea. The rolling motion of a ship has been described by a nonlinear differential equation taking into account the nonlinearities in both the restoring moment and the damping moment. Solution of differential equation of roll motion is sought using MATLAB. The effect of different representation of restoring moment on roll motion is investigated. It is seen that, the effect of different representation of restoring moment on roll motion depends on the characteristics of the GZ curve. A parametric investigation is undertaken to identify the effect of different parameters viz., wave steepness, encountering frequency etc., on the capsizing conditions of a ship. The rolling response of ship is determined in the frequency domain. The analysis has been carried out by varying both the wave steepness and the wave frequency. The approach has been demonstrated considering a Ro-Ro ship as test vessel. - PublicationNumerical simulation of ship stability for dynamic environment(01-01-2003)
; Venkata Ramana Reddy, J.The prediction of ship stability during the early stages of design is very important from the point of vessel's safety. Out of the six motions of a ship, the critical motion leading to capsize of a vessel is the rolling motion. In the present study, particular attention is paid to the performance of a ship in beam sea. The linear ship response in waves is evaluated using strip theory. Critical condition in the rolling motion of a ship is when it is subjected to synchronous beam waves. In this paper, a nonlinear approach has been tried to predict the roll response of a vessel. Various representations of damping and restoring terms found in the literature are investigated. A parametric investigation is undertaken to identify the effect of a number of key parameters like wave amplitude, wave frequency, metacentric height, etc. © 2002 Elsevier Science Ltd. All rights reserved. - PublicationSimplified model for predicting the onset of parametric rolling(01-03-2007)
; ;Lee, S. K.Sohn, K. H.The world container fleet shows the fastest growth of any ship type. The infrastructure for loading and unloading container ships are also growing in many ports around the world. Such a trend is due to the fact that the containerized transportation is becoming more and more attractive due to many factors. The increasing demand in container transportation is met by use of more number of container ships including Post-Panamax and Malacca-max containers. Loss of containers in seas and accidents of container vessels are reported from many parts of seas. New generation containers are severely hit by parametric rolling. Pure loss of stability, due to exponential increase of roll in either broaching-to or head sea conditions, is called parametric rolling, is subjected to rigorous investigation by many researchers. Algebraic expression based on well known Duffing's method is proposed for solutions in parametric rolling. The variation in GM and damping values from trough to crest conditions associated with bow flare immersion and emergence in head sea conditions with pitch resonance with the heading waves are said to be the prime reason for parametric rolling. A simple model to predict the beginning of parametric rolling is described in this paper. © 2006 Elsevier Ltd. All rights reserved. - PublicationReduction in the dynamic amplitudes of moored cable systems(12-08-2009)
; Goutam, M.Cable-body systems are intelligent and cost-effective structures used in ocean engineering and also for many oceanographic missions. The demand for such systems is increasing steadily because of new types of systems like wind farms, ocean energy converters and floating airports. Mooring of such platforms to a fixed point on the earth makes the system secure. Dynamic behaviour of a moored system with a subsurface buoy is studied here. The optimum position of the buoy is found using an analytical approach. The location of the buoy along the cable is a critical aspect in tension reduction. An analytical method is developed for the solution of a typical mooring problem taking into account the presence of a subsurface buoy. The method originally proposed by Walten and Polachek (1959) is modified here to suit the present problem. The nodal accelerations and velocities at the points of lumped mass of subsequent time steps can be expressed as per the Houbolt scheme. Integration of the accelerations and velocities lead to the solutions of the mooring-line dynamic problems subject to constraints to achieve the numerical convergence of solution. Dynamic amplitudes vary with the frequency of excitation at the surface due to external disturbances like waves and current. Wave, current and water depths are considered for the dynamic load built up along the mooring line. A number of cases are worked out, and some important and significant results are presented in this paper. Dynamic tension variations with and without a subsurface buoy are determined. Effect of pre-tension is determined and presented. Dynamic amplitude for different frequency ratios and different amplitudes of motions are determined. The method is useful for deepwater systems in which tension reduction provides better efficiency for the performance of the anchor by providing better seakeeping ability in the case of a ship or a platform. - PublicationStudy on the adequacy of scantlings of hatch covers of capsize bulk carriers and suggestions for alternate materials(01-12-2009)
; Kannan, C.Hatch cover failure leads to flooding of the forward cargo compartment and occasionally results in fatal casualty. The foremost hatch cover and the next one within 25% length of the vessel are prone to the impact by shipping of green water. The loss of hundreds of bulk carriers with the precious lives is a nightmare to both designers and insurers. The tail of Rayleigh distribution of showing the extreme rare wave heights is a matter needed great attraction of designers and analysts. Though rare, the extreme wave heights are responsible for the failure of bulk carrier ships. Deficiency in the scantling of bulk carrier covers is brought out in this paper and suggestions for betterment are proposed. Suggestions to use better material having higher strength to weight ratio is made. The tricky point is that the more we increase the strength of the hatch cover the more is its self weight. The position of vertical centre of gravity of vessel goes up and that is not desirable for commercial ships in many aspects. Unlike tanker ships decks the decks of bulk carrier ships are weakened by the presence of the hatch covers. - PublicationTechnical note Studies on the feasibilities of control of ship roll using fins(01-01-2006)
; Kiran, V.Consequences of roll motions can degrade the effective performance of a ship in a seaway. Roll motion stability becomes more critical when the moving ship encounters beam seas. Such stability is ensured using the actions of extra fins fitted to hull. Roll motion is controlled if the accelerations are high enough to cause any panicky situations for the passengers in the case of a passenger ship. Mission requirements, vessel types, loading conditions, and environmental loads cause the extent of roll and roll accelerations for a ship. In this article, the feasibility of control of roll motion using active fins is discussed. Such fins are better suited for certain types of naval ships. The stability of such vessels becomes critical during fast maneuverings and more critical in the presence of unfavorable weather conditions. Roll motion analysis on the basis of a frigate ship is performed, and proposal to reduce the roll motion using fins is also presented. Lift coefficients corresponding to various angles of attack were obtained using Fluent. Turbulence was modeled using k – ε (two-equation) model and Reynolds stress model. A number of simulations were performed for various sea conditions, and effect of ship speed on the angle of attack required for the fin to stabilize the ship was determined. Case studies were taken up with various sea states and with varying forward speeds of the ship in the beam sea. © 2006 Copyright Taylor and Francis Group, LLC. - PublicationRoll performance of a small fishing vessel with live fish tank(01-10-2005)
;Lee, S. K.; Lee, GyoungwooThe concept of live fish tanks in trawlers is to use the catch in a better condition and to reduce marine pollution. It also reduces the infrastructure meant to freeze the catch to preserve it for longer period. But the presence of additional free surface in the vessel challenges the stability of the vessel. This is besides the sloshing effect due to the moving liquid mass in the tank. Roll motions are initiated due to various factors related to the hull characteristics of the vessel, loading and operating conditions and its interaction with the environment. Location of fish tank, its orientation, arrangement of baffles inside the tank to reduce the free surface affects and careful design of tank opening are to be given priority during the design, manufacturing and tank testing. The results obtained from tank test of model are compared with that of analytical method. The non-linear roll performance become further complicated due to the free surface and sloshing effects of the mass in the live fish tank. Wave makers are used for generating waves under laboratory conditions compatible with the scaled down model of the trawler model. The tests are conducted in the towing tank of Pusan National University. © 2005 Elsevier Ltd. All rights reserved. - PublicationStudies on pullout capacity of anchors in marine clays for mooring systems(01-04-2006)
;Narasimha Rao, S. ;Hema Latha, K. ;Pallavi, B.In marine applications, single point or spread mooring systems are used for providing temporary berthing of vessels. In this investigation, it is suggested that pile anchors and suction anchors can be used depending on the water depth. By testing a model, the influence of parameters like mooring chain inclination, consistency of the clayey soil in the seabed and anchor embedment ratios on pullout capacity has been brought out. Tests were carried out on single pile, 2-pile, 4-pile anchors made out of pipe piles of 25.4 mm dia with length to diameter ratios, L / D of 10, 14 and 18 and model suction anchors (closed-top caisson) of 113 mm dia with L / D = 2, 3 and 4. These were installed in a model test bed made out of soft marine clay. The results indicate that in respect of pile anchors as of the chain inclination changes from horizontal to vertical direction, the pullout resistance shifts from passive earth pressure to skin friction. The results in respect of suction anchors can be interpreted in terms of various components proposed. © 2006 Elsevier Ltd. All rights reserved. - PublicationControl of ship roll motion by active fins using fuzzy logic(13-06-2007)
; Kiran, V.Fuzzy logic controller to reduce the roll motions of a ship using active fins is discussed in this article. Roll minimization is a requisite for various operations in the sea. Fin action provides enhanced state of stabilization especially when the vessel is performing a fast manoeuvring amidst rough environmental disturbances. The fins, in turn, are activated by electro-hydraulic mechanism based on the in-built intelligence as per suitable control theories. In this article, the fin pairs are activated using fuzzy logic control algorithm. The design of fuzzy controller is simple and need not require complicated mathematical procedures. A frigate-type warship is considered for the demonstration purpose. The control output is the fin angle. Non-linear roll motions are controlled using active fins. Fins lift characteristics in hydrodynamic flow were studied using CFD package Fluent. Input variable fuzzification, fuzzy membership functions and output set de-fuzzification are discussed in the article. A fairly good amount of reduction in roll amplitude is achieved through various simulations in random sea. The approach can be used for irregular sea conditions. © Woodhead Publishing Ltd.