R. Sundaravadivelu

Bio: R. Sundaravadivelu is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Buckling & Mooring. The author has an hindex of 9, co-authored 47 publications receiving 266 citations.

The hydrodynamic behaviour of long floating structures in directional seas

Abstract: The diffraction/radiation boundary value problem arising from the interaction of oblique waves with freely floating long structures is studied using finite-element techniques. Further, the hydrodynamic behaviour of two-dimensional horizontal floating structures under the action of multi-directional waves has been studied. The linear transfer function approach is used to determine the wave exciting forces and motion responses of a structure of finite length in short-crested seas. The directional spectrum is obtained from a unidirectional spectrum with an associated frequency-dependent or frequency-independent cosine power-type energy spreading function. Based on the numerical predictions, the motions and forces on a rectangular floating structure experiencing unidirectional and multi-directional wave fields are computed.

Wave runup on a concentric twin perforated circular cylinder

Abstract: The regular wave interaction with a twin concentric porous circular cylinder system consisting of an inner impermeable cylinder and an outer perforated cylinder was studied through physical model and numerical model studies. The experiments were carried out on the twin concentric cylinder model in a wave flume to study the wave runup and rundown at the leading and trailing edges of the perforated cylinder. It was found that the maximum wave runup on the perforated cylinder is almost same as the incident wave height. The experimental results were used to develop the predictive formulae for the wave runup and rundown on the perforated cylinder, which can be easily used for design applications. The wave runup profiles around the perforated cylinder for different values of ka and porosities were studied numerically using Green's Identity Method. The results of the numerical study are presented and compared with the experimental measurements.

Hydrodynamics of a Concentric Twin Perforated Circular Cylinder System

Abstract: An experimental investigations was carried out on a perforated circular cylinder ( 0.50 m diameter) encircling an impermeable cylinder ( 0.05 m diameter) at a constant water depth of 0.7 m for both regular and random waves in the wave flume at the Department of Ocean Engineering, Indian Institute of Technology, Madras, India. The porosity of the outer cylinder was varied from 4.54 to 19.15% to study the influence of porosity on wave forces on and water surface fluctuations in and around the twin cylinder system. A numerical method is developed based on the boundary integral equation method along with a porous body boundary condition, where the porosity is modeled using the resistance coefficient f and added mass coefficient Ca for regular waves. The resistance coefficient increases with the increase in porosity and wave heights except for a porosity of 4.54%, whereas the added mass coefficient is almost zero. Porosity in the range of 10–15% can be recommended for the perforated cylinder based on the exper...

Interaction curves for stiffened panel with circular opening under axial and lateral loads

Abstract: Stiffened panels in ships and offshore oil platforms are provided with circular openings for repair, access and maintenance. This paper presents the numerical study carried out on the ultimate strength of stiffened panel with central circular opening subjected to axial load, lateral load and a combination of axial and lateral loads. Ultimate strength of the panel was evaluated considering both geometric and material non-linearities using FEA software ANSYS. Plates of varied widths and open section unequal angle stiffeners covering plate and column slenderness ratios in the practical range of 1.0–4.5 and 0.32–1.00, respectively, keeping the opening ratio equal to 1.0 are the parameters considered in this study. On the basis of the study, interaction curves were developed for normalised axial load and normalised lateral load. The developed interaction curves for stiffened panels with angle stiffeners and circular opening were found to be non-linear for lower plate slenderness ratio up to 2.0 and for the ran...

Ultimate strength of stiffened plates with a square opening under axial and out-of-plane loads

Abstract: The high strength to weight ratio and high stiffness to weight ratio of stiffened plates find wide application in aircraft structures, ship structures, offshore oil platforms and lock gates. The strength and stability of stiffened plates is highly influenced by openings and initial imperfections. The main objective is to study the behaviour of stiffened steel plates with openings up to collapse and to trace the post-peak behaviour under axial and out-of-plane loads. Four stiffened steel plates with a square opening were fabricated for testing. Angle sections were used as stiffeners. Imperfections in the plate, stiffener and overall imperfection of the whole panel were measured. All fabricated panels were tested to failure. A finite element (FE) model was developed for the analysis of stiffened plates with initial imperfections and validated with the test results. Parametric studies were conducted using the developed FE model, and interaction curves and equations were developed for the design of stiffened plates with initial imperfections and openings. The interactive effect for stiffened panels with a square opening was found to be linear, with proportional reduction of the ultimate axial load carrying capacity due to the constant out-of-plane load.

Loads for use in the design of ships and offshore structures

Abstract: The evaluation of structural responses is key element in the design of ships and offshore structures. Fundamental to this is the determination of the design loads to support the Rule requirements and for application in direct calculations. To date, the current design philosophy for the prediction of motions and wave-induced loads has been driven by empirical or first-principles calculation procedures based on well-proven applications such as ship motion prediction programs. In recent years, the software, engineering and computer technology available to predict the design loads imposed on ships and offshore structures has improved dramatically. Notwithstanding, with the stepwise increase in the size and structural complexity of ships and floating offshore installations and the advances in the framework of Rules and Standards it has become necessary to utilise the latest technologies to assess the design loads on new designs. Along the lines of the recommendations from the International Ship and Offshore Structures Committee (ISSC) I.2 on Loads this paper reviews some of the recent advances in the assessment of loads for ships and offshore structures with the aim to draw the overall technological landscape available for further understanding, validation and implementation by the academic and industrial communities. Particular emphasis is attributed on methodologies applicable for the prediction of environmental and operational loads from waves, wind, current, ice, slamming, sloshing and operational factors. Consideration is also given to deterministic and statistical load predictions based on model experiments, full-scale measurements and theoretical methods.

Influence of corrosion on the ultimate compressive strength of steel plates and stiffened panels

Abstract: This study concentrates on a comparison between steel plate and stiffened panels subject to localised corrosion. A finite element analysis is used to investigate the effect of random corrosion on the compressive strength capacity of marine structural units. Variables include the extent of corrosion; slenderness ratio and aspect ratio. A corrosion prediction model is incorporated to determine the thickness reduction with time. Corrosion-induced volume loss results in a greater reduction of ultimate strength for slender plates compared to stiffened panels, up to 45%, showing the structural element selection can strongly influence the accuracy of the estimated corrosion damage effect.

Ocean Engineering Mechanics: With Applications

Abstract: 1. Introduction 2. Review of hydromechanics 3. Linear surface waves 4. Nonlinear surface waves 5. Random seas 6. Wave modification and transformation 7. Waves in the coastal zone 8. Coastal engineering considerations 9. Wave-induced forces and moments on fixed bodies 10. Introduction to wave-structure interaction 11. Floating bodies 12. Wave-induced motions of compliant structures.

Fuzzy sliding mode control of an offshore container crane

Abstract: A fuzzy sliding mode control strategy for offshore container cranes is investigated in this study. The offshore operations of loading and unloading containers are performed between a mega container ship, called the mother ship, and a smaller ship, called the mobile harbor (MH), which is equipped with a container crane. The MH is used to transfer the containers, in the open sea, and deliver them to a conventional stevedoring port, thereby minimizing the port congestion and also eliminating the need of expanding outwards. The control objective during the loading and unloading process is to keep the payload in a desired tolerance in harsh conditions of the MH motion. The proposed control strategy combines a fuzzy sliding mode control law and a prediction algorithm based on Kalman filtering for the MH roll angle. Here, the sliding surface is designed to incorporate the desired trolley trajectory while suppressing the sway motion of the payload. To improve the control performance, the discontinuous gain of the sliding control is adjusted with fuzzy logic tuning schemes with respect to the sliding function and its rate of change. Chattering is further reduced by a saturation function. Simulation and experimental results are provided to verify the effectiveness of the proposed control system for offshore container cranes.