Copy of this volume can be purchased from the publishing office of the journal.

Some Disturbing Aspects of Inland Vessel Stability Rules
Milan Hofman, Ivan Maksic and Igor Backalov

Design Formulation of Forward Bottom Hull Structure Due to Slamming Loads
S. Sinha, G. Rao, and S. Kar

On the Computation of Resistance of Planing Crafts Using RANS Models
N. Sulficker Ali, K. Murali and V. Anantha Subramanian

Something from Nothing ? Utilisation of ATU Condensate
Cdr AK Rohatgi and Cdr Shantanu Bose

Stability of Fluid Flow Through a Compliant Pipe : Part 1. Axisymmetric Disturbances
P.K. Sen, Munendra Kumar and A.K. Raghav

Free Vibration Analysis of Laminated FRP Composite Stiffened Plates with Arbitrary Stiffener Layout
A. Bhar and S.K. Satsangi

•  Discussions on papers published in JST

         ‘Behaviour of Ship in a Typhoon’
         ‘Effective Feedback for Better Ship Design’
         ‘Ship Recycling Activities in India – An Overview’

• Book Reviews

          ‘Early Marine Charts of India’

BACK COVER, Vol. 2, No. 2, July 2006

Some Disturbing Aspects of Inland Vessel Stability Rules
Milan Hofman, Ivan Maksić and Igor Bačkalov

ABSTRACT
Nonlinear rolling of typical inland container vessels subjected to severe beam wind was investigated in series of numerical tests. The mean wind speed was estimated from the stability rules, and the wind gusts from the appropriate wind spectrums. From the time history of vessel motion, the probability that the open container hold would be flooded was obtained. Surprisingly, it was found that inland vessels are not as safe as are seagoing ships in beam wind and waves. In some extreme but realistic circumstances, the vessels, satisfying all the present stability rules, could be flooded and eventually capsized. Such results show not only the vulnerability of inland container vessels to the severe beam wind, but also indicate some shortcomings of the present inland stability rules. A previous analysis of the same subject indicated a question: why there are no accidents of inland container vessels in severe beam storms, as the results obtained anticipated. The present investigation offers a possible, but somewhat unexpected solution to this dilemma.
Keywords:Inland container vessels, stability rules, beam wind, nonlinear rolling.

Design Formulation of Forward Bottom Hull Structure Due to Slamming Loads
S. Sinha, G. Rao, and S. Kar

ABSTRACT
Wave slamming is an important parameter for designing the forward part of the ship structure. The slamming loads are highly dynamic in nature, characterized by very short duration of the load, usually 10-20 milli-seconds and a peak value for even a shorter duration. Therefore a dynamic analysis is required to study the response of the structure. This is particularly so in case of very light and optimized structures as found on naval vessels and other high-speed vessels. Also, considering the extreme load response with a small probability of occurrence, certain amount of permanent deformation can be acceptable. This paper describes the systematic transient dynamic analysis carried out for nearly 2000 cases and proposes a simple method based on this study, for design of structures subjected to slamming loads. A Dynamic Load Factor (DLF), which converts the dynamic load into an equivalent static load, is introduced, after which a simple static analysis would yield the same results as that obtained from the dynamic analyses. The method also provides for accounting any acceptable value of permanent deformation criteria for plate thickness and presence of in-plane stresses.
Keywords: Wave Slamming, FEM, Transient Dynamic Analysis, Natural frequency, Dynamic
Load factor, Nonlinear, Elasto-plastic, Permanent deformation, Forward structure.

On the Computation of Resistance of Planing Crafts Using RANS Models
 N. Sulficker Ali, K. Murali and V. Anantha Subramanian

 ABSTRACT
This study deals with the modeling of ship- generated waves in the context of prediction of resistance of planing crafts. The free surface phenomenon around the vessel could play an important role in the resistance - both wave making and viscous. In the present study Computational Fluid Dynamics (CFD) has been used to study the effect of free surface by modeling the flow around the hull, with and without a tunnel. While using CFD for resistance computation, turbulence modeling is an important aspect and needs specific attention. Among the various available turbulence modeling schemes, the present study uses the Realizable k-e turbulence model and Reynolds stress transport model. Reynolds stress transport model, which solves for all six stress components, is found to give good prediction of frictional drag and thus total drag for planing vessels, with and without tunnel. The computational results of pressure and drag were validated against the experimental results obtained from towing tank tests on a planing hull form.

Something from Nothing ? Utilisation of ATU Condensate
CdrAK Rohatgi and Cdr Shantanu Bose

 ABSTRACT
The condensate from the Air Treatment Units of the Air Conditioning and Ventilation System in  most ships is led through the Scupper and drain system into the bilges and thereafter pumped overboard. The ATU condensate is fresh water and may be considered for effective utilization. The present paper estimates the quantity of condensate likely to be available and examines the likely areas wherein the same can be utilized for non-domestic use onboard.

Stability of Fluid Flow Through a Compliant Pipe : Part 1. Axisymmetric Disturbances
P.K. Sen, Munendra Kumar and A.K. Raghav

 ABSTRACT
The present paper discusses the stability of compliant pipe flow, considering a visco-elastic pipe having an outer rigid shroud, with Hagen-Poiseuille flow through the pipe and with axisymmetric disturbances. It includes the normal plus tangential (N+T) compliance problem and the only normal (N) compliance problem. Study of such flows can help in drag reduction on the submerged surface of ships, etc. The Sen & Arora  method is used for the only normal compliance problem. All rigid type (deviant of rigid wall) modes are stable. Unstable modes are basically either static divergence (SD) modes or transitional modes. We study in this part the stability curves for different values of the Kumaran compliance parameter G , and the solid to fluid viscosity ratio mr , for axisymmetric disturbances. The normal compliance modes are usually more unstable, and are substantially different from the normal plus tangential (N+T) compliance modes. It is also observed that wall dissipation in general tends to damp all the modes. However static divergence (SD) modes are also found at low values of Reynolds number R. For these modes the wall dissipation has virtually no effect.

Free Vibration Analysis of Laminated FRP Composite Stiffened Plates with Arbitrary Stiffener Layout A. Bhar and S.K. Satsangi

ABSTRACT
Free vibration analysis of laminated composite stiffened plates with different boundary conditions has been carried out using the finite element method. An eight-noded quadratic isoparametric plate-bending element for the plate, in combination with a three-noded quadratic isoparametric beam element for the stiffener, has been used to form a stiffened plate-bending element keeping in mind the displacement compatibilities between the plate and the stiffener. A different method of formulating consistent mass matrix for the stiffener element, which involves less computation compared to previous methods, has been derived and applied successfully to free vibration analysis. The stiffened plate element so derived is capable of accommodating stiffener placed anywhere within the plate element giving great freedom for mesh generation. The first order shear deformation theory has been used for the plate and stiffener elements. The natural frequencies obtained have been compared with those published in the literature.


Copy of this volume can be purchased from the publishing office of the journal.