Propulsion Shaft Alignment: Review and Development of Improved Procedure for Achieving Alignment Solution
Amit Batra

Application of Doublet Based Lower and Higher Order Panel Methods for Computing the Potential Flow around Two Dimensional Hydrofoil
Md. Shahjada Tarafder, Gazi Md. Khalil & Muhammad Rabiul Islam

Computation of Turbulent Viscous Flow around Submarine Hull Using Unstructured Grid
M. M. Karim, M. M. Rahman and M. A. Alim

Variability in Sound Speed Structure and SOFAR Channel Depth in the Indian Ocean
V.S Swaminathan and Prasad K. Bhaskaran

Chronology of Indian Shipping
PR Kulkarni

BACK COVER, Vol. 5, No. 1, January 2009

Propulsion Shaft Alignment: Review and Development of Improved Procedure for Achieving Alignment Solution
Amit Batra

 ABSTRACT
This paper brings out the process involved in undertaking marine propulsion shaft alignment calculations and the methodology used to carry out surveys to asses the alignment condition. The paper also defines a generalized procedure which has been devised so that the alignment checks of a shaft line can be undertaken while the ship is afloat using strain gauge measurements and results fed into an optimization algorithm to get the alignment solution. The procedure also obviates the necessity of the difficult task of assessing hull deflections. The alignment solution is obtained using two-stage 'Multi-Objective Optimization' procedure. Software titled MARSHAL has been developed, which uses finite element calculations with multi objective optimization algorithms to enable the accurate analysis and correct solutions of the shaft alignment problem.

Keywords: Propulsion shaft alignment, multi-objective optimization, strain gauges

Application of Doublet Based Lower and Higher Order Panel Methods for Computing the Potential Flow around Two Dimensional Hydrofoil
Md. Shahjada Tarafder, Gazi Md. Khalil & Muhammad Rabiul Islam

ABSTRACT
This paper deals with the doublet based lower and higher order panel methods for computing the potential flow problem around the two-dimensional hydrofoil without considering the effect of free surface. Using Green's second identity the Laplace equation is transformed into an integral equation in terms of a distribution of singular solutions, such as doublets on the boundaries. After satisfying the boundary conditions the integral equation can be written into a matrix form and the matrix is solved by Gaussian Elimination procedure. The Kutta condition is applied at the trailing edge of the lifting body to generate required circulation which is constant across the wake surface. The validity of the computer scheme is examined by comparing the numerical results with the analytical as well as experimental results of van de Vooren, NACA 0012 and NACA 4412 hydrofoils. In comparison to the higher order method, the use of the lower order method results in fewer numerical manipulations and each method has the problem near the trailing edge of the hydrofoil.

Keywords: Panel method, Hydrofoil, potential flow, numerical hydrodynamics

Computation of Turbulent Viscous Flow around Submarine Hull Using Unstructured Grid
M. M. Karim, M. M. Rahman and M. A. Alim

ABSTRACT
This paper presents finite volume method based on Reynolds-averaged Navier-Stokes (RANS) equations for computation of 2D axisymmetric flow around bare submarine hull using unstructured grid. The body used for this purpose is a standard DREA (Defence Research Establishment Atlantic) bare submarine hull. Shear Stress Transport (SST) k-w model has been used to simulate turbulent flow past the hull surface. Finally, computed results using unstructured grid are compared with those using structured grid and also with published experimental measurements. The computed results show good agreement with the experimental measurements.

Keywords: axisymmetric body of revolution, underwater vehicle, unstructured grid, viscous drag, CFD, turbulence model

Variability in Sound Speed Structure and SOFAR Channel Depth in the Indian Ocean
V.S Swaminathan and Prasad K. Bhaskaran

ABSTRACT
The present work reports estimation of sound speed structure and variability in SOFAR (Sound Fixing and Ranging) channel depth for the Indian Ocean. The study is based on inter-comparison of the above using the state-of-art WOA (World Ocean Atlas) and a comprehensive ocean atlas for Indian Ocean (new climatology) recently developed for the Indian Ocean. The new climatology is more robust because in-situ data of temperature and salinity as function of depth for a period of approximately five years obtained from the randomly deployed ARGO profiling floats is embedded in its formulation. As sound speed profile in real ocean is sensitive to variation in temperature (T), salinity (S) and water pressure (D), the new climatology provides an opportunity to skill assess sound speed structure and SOFAR channel for the Indian Ocean with the existing state-of-art WOA. An inter-comparison study was then performed for two contrasting months of January and July which reveals a difference of +0.5 ms-1 for a larger area in the Indian Ocean, with maxima-minima centered at ± 3ms-1 for both these months. It should be emphasized here that these differences are due to inclusion of in-situ ARGO data in preparation of the new climatology. Further, the study advocates differences in the computed monthly averaged SOFAR channel depth with immense application potential for underwater communication.

Keywords: SOFAR channel, WOA, New Climatology, ARGO, Comparison

Chronology of Indian Shipping
PR Kulkarni

ABSTRACT
Sequential arrangement of events in their order of occurrence with respect to a time line constitutes a chronology. As the author of this paper set about to piece together a linear representation of the progress of Indian shipping and shipbuilding in a chronological outline of certain historical events that have shaped its evolution, the authentic and verifiable data was hard to come by. The only such data, which would nodoubt have been compiled after painstaking research, was found in one of the sections of the book by NG Jog titled "Saga of Scindia". The book is a record of the first fifty years of the pioneers of Indian Shipping, the Scindia Steam Navigation Company Limited, which celebrated the Golden Jubilee on 27 March 1969. Accordingly, NG Jog presents the Chronology of Indian Shipping only up to 1969 in his book. There is a need for updating the events associated with Indian Shipping beyond 1969 and convert it into a Chronology of Indian Shipping and Shipbuilding. It is also found that some milestones within the timeline covered by NG Jog, have not been recorded. Attempts to revise and update the chronology by the author, by approaching the various agencies/authorities have not been successful. Our maritime history is not a matter of chance or of casual growth: it is a heritage. It is a heritage that must be guarded jealously and studied carefully in all its phases. Towards such an objective, it is hoped that this chronology, reproduced from NG Jog's book, motivates the readers to compile and update the chronology of Indian Shipping and Shipbuilding.

Keywords: Chronology, Indian Shipping, Maritime History