SWATH Ship Design Formulae Based on Artificial Neural Nets
Volker Bertram, Ehsan Mesbahi

Study of Design Solutions to the Problem of Ballast Water
S. Mukherjee, O.P. Sha and S.C. Misra

Design of a Comprehensive Underwater Target Classifier for Passive Sonar
Arnab Das, Arun Kumar, Rajendar Bahl

Application of Bio-Diesel in Marine Engines-An Attempt to Comply with the MARPOL Act
B.V. Appa Rao, P.V.Rao, Ch. Satyanarayana, S.Chandra Prasad

Warship Design and Technology Imperatives for Emerging Navies
Cdr G Srinivasan, Cdr SS Vombatkere

Stability of Fluid Flow Through a Compliant Pipe : Part 2. Non-Axisymmetric Disturbances
P.K. Sen, Munendra Kumar and A.K. Raghav

Cavity Length Prediction of Full Cavitation Model
Anil Rawat, S. K. Dash

• Discussions on papers published in JST

‘Dynamic Analysis of Articulated Floating Bridge’
‘Study of Problem of Exhaust Smoke Ingress into GT Intakes of a Naval Ship’

• Book Reviews

'Saga of Scindia'

BACK COVER, Vol. 3, No. 1, Jan 2007

SWATH Ship Design Formulae Based on Artificial Neural Nets
Volker Bertram, Ehsan Mesbahi

ABSTRACT
Simple design formulae for resistance and power prediction for SWATH ships are derived using Artificial Neural Networks. These formulae can be programmed easily in spreadsheets or optimization routines. The formulae were derived from a database compiled at ENSIETA and are supplemented by previous work. The experience with the presented applications shows that artificial neural nets often allow a better approximation of data than classic regression analysis, but this is largely due to the more adaptable functional relations.

Keywords : SWATH, resistance, power prediction, design formulae, Artificial Neural Networks, polynomials

Study of Design Solutions to the Problem of Ballast Water
S. Mukherjee, O.P. Sha and S.C. Misra

ABSTRACT
Ballast water has been a necessity for every sea-going vessel. It is only in the last two decades that the invasion of non-indigenous biological species has been recognized to be a global problem. Mid-ocean exchange and treatment of ballast water coupled with monitoring that exists today is referred to as Ballast Water Management. The current paper tries to establish a new methodology to deal with the problem at the ship design stage. The idea is to keep the ballast tank open to the sea and simulate a situation of controlled damage. The scenario is similar to that of "lost buoyancy". The flow within the vessel is used to achieve the recycling of water. The paper discusses the feasibility, exchange and impact (on resistance) of the alternatives in design. The study shows that the concept can be successfully extended to sea-going vessels.

Keywords: Ballast water, exchange, ballast-less, model ballast tanks, barge, diffusion.

Design of a Comprehensive Underwater Target Classifier for Passive Sonar
Arnab Das, Arun Kumar, Rajendar Bahl

ABSTRACT
The overall design of an underwater target classifier for use with a passive sonar is presented in this paper. To be able to classify a particular platform is the ultimate aim. However due to the severity of the underwater channel and other complex issues, there are difficulties in achieving the ultimate goal. Thus we propose some intermediate classes based on certain parameters, which also have lot of potent information for any naval battle scenario. As a first cut we classify the platforms based on their propulsion type. In the next step we propose to identify the subclasses within the propulsion type. For quick classification decision one needs to compromise on reliability as the Signal-to-Noise Ratio (SNR) enhancement process involves averaging dependent on frame length. Additionally, transient detection and classification has been proposed for differentiating biological noise from transients like torpedo hatch opening or door
opening inside a submarine. Active transmission can be encountered sometimes and it is desirable to detect the active waveform to be able to identify the transmitter. In the proposed design all such factors have been kept in mind to evolve a classifier design that is optimal both in terms of reliability and fast decision-making and comprehensive to be able to give as many target parameters as possible.

Keywords : Comprehensive Underwater Target Classifier, transient detection and classification, feature extraction, pre-processing, passive sonar classifier, SNR enhancement.

Application of Bio-Diesel in Marine Engines-An Attempt to Comply with the MARPOL Act
B.V. Appa Rao, P.V.Rao, Ch. Satyanarayana, S.Chandra Prasad

ABSTRACT
Bio-diesel application in Marine diesel engines has gained importance in the recent years in the light of marine pollution. Any bio-diesel emits more NOX than what diesel fuel does because of the oxygen content implicit in the molecular structure and there is insignificant or total absence of SOX emission. NOX can be reduced in several ways. In the present study, a trial was made on a laboratory-based direct injection diesel engine with neat Jathropha Methyl Ester (JME) and JME plus H2O vapor. The super heated water vapor (in varied quantities) at 4500 centigrade was introduced in the inlet manifold along with the air during suction. The engine performance and exhaust emission were studied when the engine was tested (at no load and ¾ load) with petroleum diesel, neat JME and JME plus H2O vapor. The cylinder head vibrations were recorded to analyze the knocking and detonation aspects of the engine at selected loads. From the investigations it was observed that water fumigation successfully reduces the dangerous ‘NO’ emission without engine modification and with the retrofit of water evaporator called fumigator.

Keywords: Bio-diesel, JME, water fumigation, exhaust emissions , Heat Release Rate (HRR), cylinder vibration.

Warship Design and Technology Imperatives for Emerging Navies
Cdr G Srinivasan, Cdr SS Vombatkere

ABSTRACT
Navies traditionally function along a quadrangular grid with the military role
underpinning three complementary roles – the politico-diplomatic, the constabulary and the benign. However, globalisation has given birth to a geo-economic based military paradigm that has manifested in an increasing degree of multilateral naval cooperation, resulting in navies operating together in coalition even though they are not part of any military alliance. As a consequence regional states with emerging navies , having a strong desire to be reckonable maritime powers, are emerging as pivotal role players with an increasing say in international affairs. Emerging navies are therefore required to acquire capabilities commensurate with their new perceived role. These navies are resorting to warship acquisition in the short term and indigenous warship construction & allied military programmes in the long term in an attempt to reduce their historical dependence on developed countries. However, in this endeavour emerging navies are subject to numerous constraints, which mandate a set of imperatives for naval planning and warship design that are considerably different from established norms . This paper examines the constraints of emerging navies within the framework of the new military paradigm vis-à-vis the existing processes of naval planning and warship design. The purview of the paper would be limited to the imperatives of warship design in this context.

Key words : Warship Design, Warship Technology, Emerging navies, Design Imperatives, Indigenisation, Technology insertion, Technology Imperatives, Obsolescence.

Stability of Fluid Flow Through a Compliant Pipe : Part 2. Non-Axisymmetric Disturbances
P.K. Sen, Munendra Kumar and A.K. Raghav

ABSTRACT
The present work discusses the hydrodynamic stability of compliant pipe flow, considering a visco-elastic pipe, with an outer rigid shroud, and with Hagen-Poiseuille flow through the pipe. It includes the normal compliance studies by Sen and Arora [1] method, physical realisability studies by the equivalent plate-spring model, normal (N) compliance studies for the full viscoelastic wall. Here, only non-axisymmetric disturbances have been considered. The coupled fluid-solid equations have been solved numerically by the Sen and Arora [1] method. Stability of surface flow of a ship can be used to set up criteria for drag reduction on such bodies, requiring special surface materials. Here we also study the neutral stability curves for different values of the Kumaran compliance parameter G and the solid-to-fluid viscosity ratio m. However, the normal (N) compliance modes are more unstable and are substantially different from the normal plus tangential (N+T) compliance modes. It is also observed that wall dissipation tends to damp all the modes.

Keywords : Flow stability, compliant pipe, N-T compliance, divergence modes, flexible structure,
drag reduction.

Cavity Length Prediction of Full Cavitation Model
Anil Rawat, S. K. Dash

ABSTRACT
In the present paper an effort is made towards an approach that enables designers to eliminate, reduce or shift the cavitation regions over a hydrofoil using a cavitation model available in a commercially available CFD software. All numerical results were first validated with the experimental results for 2D NACA 66 (MOD) hydrofoil, and a conical submerged body. The general characteristics of the cavitating flow are very well predicted. In particular, the cavity length is calculated with high accuracy. Once the validity of the cavitation model available in the CFD software was established, the performance of the NACA 65 section was studied numerically by comparing the results with those obtained for NACA 66 (MOD) hydrofoil. With this approach, commercially available CFD software such as Fluent can be used as a valuable prediction tool, at an early stage of the hydrofoil design, for design verification and optimization and to predict cavitation related surface damage, which may affect the life of the equipment.

Keywords : Cavitation, cavitation model, cavity length, CFD, hydrofoil.

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