Subrata Bhattacharya

Indian Institute of Technology Madras | IIT Madras · Department of Ocean Engineering

The current research article presents the experimental investigation to comprehend the critical suction height and the region influenced by flow around particles during the hydraulic collection of polymetallic nodules (PMNs). The present investigation employed a water jet-eductor driven suction pipe to collect PMNs from the deep sea bed. Rectangula...

The wavenumber–frequency spectra (WFS) of turbulent wall pressure fluctuations are used to design underwater acoustic systems, and a method is presented to determine them for flat plate flow using large-eddy simulations (LES). First, the Reynolds averaged Navier–Stokes (RANS) analysis is carried out for flow over the plate using k–ω shear-stress tr...

High density polyethylene pipe has been used to draw coldwater for low temperature thermal desalination plants since the year 2006 at Lakshadweep Islands, India. The pipeline endured in-line oscillations due to shear current in one of the desalination plants, and this gave an opportunity to observe the response parameters of the prototype pipeline....

Flow-induced aerodynamic noise from four cylindrical shapes of infinite length at a low subcritical flow regime is studied using Large Eddy Simulation (LES) and acoustic analogy. Numerical simulations are performed for short-span (length to diameter ratio of 3) cylinders, and a sound correction method based on equivalent/spatial coherence length ha...

The normal mode method is widely used in ocean acoustic propagation. Usually, finite difference and finite element methods are used in its solution. Recently, a method has been proposed for heterogeneous layered waveguides where the depth eigenproblem is solved using the classical Rayleigh–Ritz approximation. The method has high accuracy for low to...

Heave plates are widely used in floating offshore structures to reduce the heave motion by increasing heave damping and heave added mass, and these parameters are sensitive to the amplitude and frequency of heave motion. It is important to obtain the hydrodynamic parameters, namely, damping and added mass of the floater not only at its natural freq...

Estimation of aerodynamic as well as hydrodynamic noise from an infinitely long circular cylinder subjected to low Reynolds number sub critical flow regime is detailed in this study. Large Eddy Simulations were performed on a smaller cylinder span length and correction factors were applied to account for the sound generated from longer span lengths...

Spar, tension leg platform, and semi-submersibles use heave plates to reduce heave response by increasing heave damping and added mass. Conventional practice is to use a linear damping ratio, which is typically obtained from free heave decay tests or Computational Fluid Dynamics (CFD) simulations. However, with the addition of heave plates, the sys...

Numerical studies were performed to establish relationship between far field noise and spatial coherence length () for circular cylinders in the subcritical flow regime. Hybrid methods involving Large eddy simulations and acoustic analogy was used to estimate aerodynamic noise from circular cylinders for various Reynolds numbers (Re) between 3900 t...

The vortex induced vibration of slender cylindrical structures is common in offshore structures and marine applications such as risers, towing cables, etc. The VIV response of such slender elements in steady uniform current has been investigated in the past using numerical and experimental studies. Though few numerical studies exist for varying cur...

Aerodynamic noise from circular cylinder subjected to uniform flow of Reynolds number (Re) 19800 was predicted numerically. Large Eddy Simulations (LES) and Ffocws Williams-Hawkings (FWH) analogy was used to predict the far field pressure fluctuations and further the far field sound. Shorter span length of cylindrical section was used for the numer...

Dynamic Positioning System (DPS) is a critical component of marine vessels and floating platforms that are used in offshore operations. It is a computer-controlled system that automatically maintains a ship’s position and heading using thrusters fitted to the ship. Reliability assessment of DPS can be analyzed through conventional fault tree analys...

This special issue presents a remarkable collection of papers on ‘coupled dynamic analysis of floating structures with concept technologies: current status and emerging future trends’.

Estimation of roll damping of ships from free roll decay experiments or using appropriate semi-empirical formulae is a common practice. The total roll damping of a ship or a barge can be strongly nonlinear consisting of linear and nonlinear components; especially when bilge keel is fitted to the hull as a damping device and also when angles of roll...

Ships are prone to large roll motions in beam and oblique seas at encounter frequencies near the design frequency of the vessel. The nonlinearity of roll damping and roll motion has been investigated in the past by various researchers. The prediction of roll damping and roll motion of ships becomes difficult by simplified approaches. Ship roll moti...

Unburied flexible pipelines are deployed for conveying the cold water for desalination process in coral island. Generally, high-density polyethylene material is used as cold water pipeline, where the pipelines could not be buried in coral seabed considering its buoyancy in seawater and simplistic in deployment configuration. However, such pipelines...

A method of optimizing the cost and reliability of a system represented by a fault tree is proposed which is useful in choosing the technology options for basic events that are available to the system designer. The problem of optimization is to minimize the overall system cost by exercising technology choices that will yield a prescribed probabilit...

Depth dependence of sound speed is integral to the study of most phenomena pertaining to waveguide propagation in ocean acoustics. The normal mode method has widely been used to study depth dependent acoustic waveguides. The depth eigenproblem associated with the normal mode approach could be solved exactly only for a few cases. The well-known KRAK...

In this paper the results of CFD simulations, that were carried out to study the impact pressures acting on a symmetric wedge during water entry under the influence of gravity, are presented. The simulations were done using a solver implementing finite volume discretization and using the VOF scheme to keep track of the free surface during water ent...

The water impact and subsequent entry of three rigid axisymmetric bodies, a sphere and two cones, in the early phase are simulated using CFD utilizing a VOF scheme to track the free surface and the results compared with the recent experimental results available in the literature. The penetration depth, vertical velocity and vertical acceleration ti...

Drag and flow-induced sound reduction on a circular cylinder fitted with splitter plate is numerically studied. The numerical simulations of the cylinder, without and with splitter plate, have been carried out at subcritical Rey-nolds number (Re) of 97,300 using large eddy simulation (LES). Ffowcs Williams and Hawkings (FW-H) acoustic analogy has b...

The paper presents aeroacoustic results for the flow around finite-length circular cylinders at Reynolds number 84 770 for various length-to-diameter (L/D) ratios (= 3, 9, 20, 25, 30, and 35). The incompressible Navier-Stokes equations are solved using the large eddy simulation model of turbulence followed by acoustic predictions in the far field u...

Bilge keels are commonly used as roll mitigation device in ships, barges and FPSOs. The assessment of damping of a floating body can be carried out using free oscillations at natural frequency and forced oscillations for other frequencies. Various parameters like roll center, radius of gyration and the appendages attached to the hull may affect the...

This paper presents a probabilistic failure analysis of leakage of the oil and gas in a subsea production system using fault tree analysis (FTA). A fault tree was constructed by considering four major areas where the leakages can be initiated. These are: gas and oil wells, pipelines, key facilities and third party damage. Conventional FTA requires...

This paper adopts Genetic Algorithm (GA) -driven optimisation framework to solve the design optimisation problem of an autonomous underwater vehicle that aims to minimise the delivered power under the constraints on the geometric parameters that define the hull shape. The GA and computational fluid dynamics (CFD) solvers are seamlessly integrated i...

A multi-objective optimization framework is developed for design of submarine hull shape. Internal volume of the vehicle and its hydrodynamic drag are optimized by seamlessly integrating non-dominated sorting genetic algorithm and Reynolds averaged Navier–Stokes solver in a single code. The methodology seeks a geometric shape with minimum drag and...

Underwater gliders are buoyancy propelled vehicle which make use of buoyancy for vertical movement and wings to propel the glider in forward direction. Autonomous underwater gliders are a patented technology and are manufactured and marketed by corporations. In this study, we validate the experimental lift and drag characteristics of a glider from...

This paper presents a study on the line heating simulation process with an efficient "finite element analysis (FEA)" simulation model. The simulation model is conceived using concepts from three dimensional (3D) FEA of heat and mass transfer, plate theory and geometry, and implemented with commercially available software (Ansys*™ Mechanical APDL)....

Linear damping models have been used in the past for solving floating body dynamics, especially for simple geometries such as spar. However, due to the addition of heave damping elements to spar such as heave plate, complex flow around these elements may change the relationship between damping and velocity of the body to nonlinear. The damping play...

The prediction of nonlinear roll motion of ships depends highly on the accurate estimation of roll damping. The nonlinear nature of roll damping arises from the viscous flow and the associated phenomenon of flow separation around the ship hull. Roll damping changes noticeably with a slight change in the ship hull geometry and appendages. The estima...

Underwater gliders are buoyancy propelled vehicle which makes use of buoyancy for vertical movement and wings to propel the glider in the forward direction. AUGs are patented and are manufactured and marketed by corporations. To date, there had been no research in India towards its development. Also, there is no literature on the development of a v...

The most common method of reducing roll motion of ship-shaped floating systems is the use of bilge keel which act as damping elements. The estimation of the damping introduced by bilge keel is still largely based on empirical methods. The present work adopts the CFD approach to the estimation of roll damping, both without and with bilge keel and va...

Oil exploration that initially started ashore has now moved well into deeper offshore areas due to reduced possibilities of new fields in shallower waters. Increasing demand of oil and gas exploration leads offshore drilling and production of hydrocarbon deposits towards greater water depths. Exploration process shall become cost effective by emplo...

Flow past a rectangular cylinder at a Reynolds number of 1,33,000 has been studied numerically using the large-eddy simulation technique. The Smagorinsky-Lilly model stress model has been used for the small scales of turbulence. The objective of this work was to develop a CFD model to compute the generated aerodynamic noise from rectangular cylinde...

This paper presents an optimization model that incorporates a clash free mechanism for design of Autonomous Underwater Vehicles/Gliders (AUVs/Gs). The present model allows the designer to pack the internal components satisfying the stability and buoyancy criteria and integration of Computer Aided Design (CAD) and Computational Fluid Dynamics (CFD,...

In the present work, reliability of the software Mirtoolbox that was developed for music signal processing has been investigated into. Motivation for the work stems from the fact that performance report of the software is not available in the literature from sources other than the developers of the software. A few functions available in the softwar...

Analytical solutions of the normal modes for acoustic wave propagation in shallow water homogeneous ocean overlying an interacting semi-infinite solid half space consisting of homogeneous, isotropic soil or rock are studied in this paper. The effects of the three parameters, namely, water depth, mechanical and acoustic properties of seabed and sour...

The ocean acts as an acoustic waveguide (WG) bounded at the top by the sea surface and the bottom by the seafloor. The sound speed and density may in general vary spatially, in particular across the depth of the water column. Sound speed variation in a WG plays a significant role in acoustic propagation. In this paper, we consider depth dependence...

The present work is aimed at CFD simulation and experimental study on frequency and amplitude dependency of heave damping of Spar hulls by forced oscillation along heave direction in calm water condition. Conventionally, the heave damping is obtained by free decay test of a scale model which gives damping only at the heave natural frequency, but th...

Roll motion of ships and ship-like floating bodies is subject of interest since a long time. The roll motion and the related damping becomes highly unpredictable, unlike other motions. This is mainly due to the non-linear effects arising from the viscous flow around the hull and the appendages attached to it. Various roll motion mitigation devices...

Underwater glider moves vertically by change in buoyancy and moves horizontally due to wings. In this paper, we validate the experimental lift and drag characteristics of a glider from the literature using Computational Fluid Dynamics (CFD) approach. This approach is then used for the assessment of the steady state characteristics of a glider under...

This paper presents a multi-objective optimization design framework that is integrated with the Computer Aided Design (CAD) for geometric variation and Computational Fluid Dynamics (CFD) software for hydrodynamic computations for the design of Autonomous Underwater Vehicles (AUVs). The optimization model utilizes the ‘Non-dominated Sorting Genetic...

A review of the recent progress made regarding ocean environmental data and models with uncertainties in focus is given in the perspective of marine structures׳ design and operations. Uncertainties of wind, waves, current, sea water level and ice data and models are discussed and recent achievements leading to improvement of their accuracy are addr...

A recently developed deterministic FE model for range and depth dependent acoustic waveguides (Vendhan et al, J. Acoust. Am., 126, 3319–3326, 2010) may be extended to a medium with random properties. Such a model would require the eigensolution for a depth dependent waveguide at the far field of the FE domain. The aim of the present paper is to stu...

The numerical study of water entry of a three dimensional (3D) rigid wedge under free fall is carried out, by finite volume discretization and volume of fluid (VOF) scheme to keep track of the free surface, by using a commercial solver. The different hydrodynamic parameters of the rigid wedge when it strikes the liquid surface under the action of g...

A computational toolbox to study the behaviors of underwater sound propagation using MATLAB having graphic user interface. The toolbox is named as “COAT”.

The design of 'Autonomous Underwater Vehicles (AUVs)' is mission specific and it is getting more and more complex with time because of higher demands of range, endurance, payload, operation flexibility, navigational capabilities for deep and restricted water depths, energy efficiency and special mission requirements as placed by the user agencies....

This paper presents a 3D (three dimensional) ‘Finite Element Analysis (FEA)’ model for the prediction of residual deformation due to line heating in metal plate forming processes that are common and preferred choice of manufacturing in shipbuilding, automotive and aerospace industries. The spatial and temporal discretizations have significant effec...

Damping elements are used in ships and offshore structures as response reduction devices for maintaining the motion response within acceptable limits. The design of these elements relies on a combination of empirical approach and past experience. In this paper, an investigation of the wave excitation and hydrodynamic reaction forces acting on float...

The aim of this special issue is to present the recent approaches and results in research and technology related to deep water offshore structures. In this issue, we focus on new research results that are either of theoretical or of applied nature and illustrate the current forefront of research, education, and practice in ‘‘Structural Analysis of...

In shallow water ocean, the acoustic waves interact with seabed sediment or rock layers along the propagation path. In this paper, the dispersive properties of wave propagation in an ocean consisting of a fluid layer with constant sound speed overlying a semi-infinite solid elastic (sediment or rock) layer with constant compressional and shear wave...

A computational fluid dynamics approach to study drag reduction of axisymmetric underwater bodies by air jet injection in the boundary layer is presented. The well-known ‘mixture’ model is used to capture the multiphase flow and the SST k-ω (shear stress transport) turbulence closure model has been used in the computations. Well-studied Afterbody1...

Drag reduction on underwater vehicles is a problem of practical significance studied for decades. Appreciable work had been done in past, but complexity of problem had prevented significant reduction due to turbulence and multiphase flow characteristics. Air injection in underwater vehicles had been proved to be most efficient technique in comparis...

Damping elements are used in ships and offshore structures as response reduction devices for maintaining the hydrodynamic response within acceptable limits. The use of such elements so far has been based on past experience or using empirical based design approach. An investigation of the wave excitation forces acting on these structures with and wi...

A fuzzy autopilot algorithm for maneuvering of surface ships is proposed and its performance studied. A mathematical model for nonlinear maneuvering of cargo ships has been used in conjunction with the proposed fuzzy autopilot. The autopilot works with two error measures that are inputs, error in heading angle and the offset error from the desired...

This paper addresses the Computational Fluid Dynamics Approach (CFD) to simulate the flow over underwater axisymmetric bodies at higher angle of attacks. Three Dimensional (3D) flow simulation is carried out over MAYA Autonomous Underwater Vehicle (AUV) at a Reynolds number (Re) of 2.09×10 6 . These 3D flows are complex due to cross flow interactio...

Damping elements have been in use as heave damping devices in offshore structures to reduce the motion response. Vortex formation and shedding around these elements in turbulent flow is the key to their effectiveness as damping elements. The understanding of flow pattern and the magnitude of flow variation around them may be useful to improve the d...

This paper presents a computational fluid dynamics (CFD) approach to the calculation of translational added mass coefficient of axisymmetric underwater bodies in both longitudinal and transverse directions. The proposed method involves CFD simulations of accelerated as well as uniform flows past axisymmetric bodies based on Reynolds averaged Navier...

The estimation of the motion response of a floating semi-submersible type offshore platform for a desalination plant, of capacity 10 million litres per day (MLD) of fresh water, is the focus of the study. The platform needs station keeping by a mooring system using a spar moored in deep water. To cater to these requirements, several design configur...

A method is presented to determine the response of a spherical acoustic transducer that consists of a fluid-filled piezoelectric sphere with an elastic coating embedded in infinite fluid to electrical and plane-wave acoustic excitations. The exact spherically symmetric, linear, differential, governing equations are used for the interior and exterio...

Ship dynamics in ocean waves involve frequency-dependent added mass and radiation damping which can be estimated either by potential theory-based calculations or by experiments. With uniform forward speed, the added mass and damping matrices become asymmetric. In this paper, we attempt to use a system identification approach, specifically the rever...

This paper deals with the application of nonparametric system identification to the nonlinear maneuvering of ships using neural network method. The maneuvering equations contain linear as well as nonlinear terms, and one does not attempt to determine the parameters (or hydrodynamic derivatives) associated with nonlinear terms, rather all nonlinear...

This paper deals with the application of nonparametric system identification to a nonlinear maneuvering model for large tankers using artificial neural network method. The three coupled maneuvering equations in this model for large tankers contain linear and nonlinear terms and instead of attempting to determine the parameters (i.e. hydrodynamic de...

A parametric identification method for the estimation of hydrodynamic derivatives embedded in the nonlinear steering equations for ship maneuvering in calm seas is presented. The models developed for identification involve determination of constant, "low-frequency" hydrodynamic derivatives. The method is robust, noniterative, and computationally li...

Dynamics of a large moored floating body in ocean waves involves frequency dependent added mass and radiation damping as well as the linear and nonlinear mooring line characteristics. Usually, the added mass and radiation damping matrices can be estimated either by potential theory-based calculations or by experiments. The nonlinear mooring line pr...

Process plants deal with hazardous (highly flammable and toxic) chemicals at extreme conditions of temperature and pressure. Proper inspection and maintenance of these facilities is paramount for the maintenance of safe and continuous operation. This article proposes a risk-based methodology for integrity and inspection modeling (RBIIM) to ensure s...

A new frequency domain system identification method for estimation of hydrodynamic derivatives embedded in linear steering equations for ship maneuvering in calm seas is presented. The frequency domain multiple input-single output models developed for identification involves determination of constant, 'zero-frequency' hydrodynamic derivatives. The...

Role of mini tension leg platforms (TLP) in oil exploration and production in marginal deepwater fields is becoming increasingly important. Mini TLP combines the simplicity of a spar and favorable response features of a TLP. In this paper, the results of a detailed experimental and numerical investigation of the coupled dynamic behavior of a mini T...

In a domain method of solution of exterior scalar wave equation, the radiation condition needs to be imposed on a truncation boundary of the modeling domain. The Bayliss, Gunzberger, and Turkel (BGT) boundary dampers, which require a circular cylindrical and spherical truncation boundaries in two-(2D) and three-(3D)-dimensional problems, respective...

Dynamics of a large moored floating body in ocean waves involves frequency dependent added mass and radiation damping as well as the linear and nonlinear mooring line characteristics. Usually, the added mass and radiation damping matrices can be estimated either by potential theory-based calculations or by experiments. The nonlinear mooring line pr...

The role of mini tension leg platforms (TLP) in oil exploration and production in marginal deepwater fields is becoming increasingly important. SeaStar is a mini TLP that combines the simplicity of a spar and favourable response features of a TLP. In this paper, the results of a detailed numerical investigation of the coupled dynamic behaviour of S...

The coupled nonlinear dynamic analyses of a Mini Tension Leg Platform (Mini TLP) using Morison wave force model as well as diffraction effects combined with Morison wave forces are presented. The computed motion as well as dynamic tether tension response amplitude operators (RAOs) are validated by tests conducted on a 1:56 scaled model tethered in...

In a domain method of solution of exterior scalar wave equation, the radiation condition needs to be imposed on a truncation boundary of the modeling domain. The Bayliss, Gunzberger, and Turkel BGT boundary dampers, which require a circular cylindrical and spherical truncation boundaries in two-2D and three-3D-dimensional problems, respectively, ha...

Conventional tow fishes are commonly employed in underwater instrumentation and surveys. However, due to uncommon functional requirements, towed bodies, which are not of the conventional and established shapes have to be used. In such cases, the roll and pitch orientation of the body, its stability and depth of operation are the important criteria...

In a domain method of solution of exterior scalar wave equation, the radiation condition needs to be imposed on a truncation boundary of the modelling domain. The Bayliss, Gunzberger and Turkel (BGT) boundary dampers of first- and second-orders, which require a circular cylindrical truncation boundary in the diffraction-radiation problem of water w...

The determination of the drag and inertia coefficients, which enter into the wave force model given by Morison's equation, is particularly uncertain and difficult when a linear spectral model is used for ocean waves, and the structure is compliant and has nonlinear dynamic response. In this paper, a nonlinear System Identification method, called Re...

Direct measurement of the wave kinematics in laboratory and field has always occupied a central place in experimental research in water waves. In this paper, a laboratory scale, multi-stage three component Perforated-ball Velocity Meter (PVM) has been used to measure the wave kinematics in linear as well as nonlinear waves, in long crested as well...

Studies on wave propagation in cylinders have a long history [M. J. Berliner and R. Solecki, J. Acoust. Soc. Am. 99, 1841-1853 (1996)]. Onoe et al. [J. Appl. Mech. 29, 729-734 (1962)] studied the attenuating and propagating modes of an isotropic cylindrical rod. Mirsky [J. Acoust. Soc. Am. 37, 106-1021 (1965)] presented the solution for harmonic wa...

In a domain method of solution of exterior scalar wave equation, the radiation condition needs to be imposed on a truncation boundary of the modeling domain. The Bayliss, Gunzberger and Turkel (BGT) boundary dampers (1982), which require a circular cylindrical truncation boundary in the difffraction-radiation problem of water waves, have been parti...

Role of mini tension leg platforms (TLP) in oil exploration and production in marginal deepwater fields is becoming increasingly important. The choice of wave force model in the analysis of such structures could either be the Morison's equation or linear diffraction-radiation theory depending on the wave frequency range. In this paper, coupled nonl...

The dynamics of underwater towing of flexible cylindrical structures belongs to the class of fluid-structure interaction problems commonly referred to as ``cylinders in axial flow''. The serious concern in such towing operations is the various types of hydroelastic instabilities exhibited by the structure at certain critical tow speeds. In practice...

Numerical modelling of exterior acoustics problems involving infinite medium requires truncation of the medium at a finite distance from the obstacle or the structure and use of non-reflecting boundary condition at this truncation surface to simulate the asymptotic behaviour of radiated waves at far field. In the context of the finite element metho...

A Perforated-ball Velocity Meter (PVM) device measures the wave induced forces on a cantilevered ball-tube assembly and the wave kinematics is computed from these forces by solution of an inverse problem given by the Morison's equation. The drag and inertia coefficients of both the ball and the tube are experimentally determined and the forces on b...

Bodies under impulsive motion, immersed in an infinite acoustic fluid, severely put to test any numerical method for the transient exterior acoustic problem. Such problems, in the context of the finite element method FEM, are not well studied. FE modeling of such problems requires truncation of the infinite fluid domain at a certain distance from t...

A perforated-ball velocity meter (PVM) has been developed for measuring all three components of water particle velocities at five different vertical locations simultaneously in regular, long crested as well as short crested free surface wave field in laboratory scale. The device measures the wave induced forces on a cantilevered ball-tube assembly....

This paper is concerned with the computation of second order steady hydrodynamic forces experienced by floating bodies exposed to regular waves. A finite element method developed earlier for the linear diffraction-radiation problem of floating bodies in the frequency domain has been extended to build the capability for calculating second order mean...

The dynamics of flexible slender circular cylinders in axial flow having regard to their fluidelastic instability characteristics is an extensively studied problem in the literature. A finite element formulation of the problem is presented in this paper. The formulation has been validated with the analytical results of supported cylinders available...

A block equation solver for the solution of large, sparse, banded unsymmetric system of linear equations is presented in this paper. The method employs Crout variation of Gauss elimination technique for the solution. The solver ensures the efficient use of the available memory by doing block factorization and storage. It uses a skyline storage sche...