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

Behaviour of a Ship in a Typhoon
Cdr PR Kulkarni

Transient dynamic finite element analysis of plate panelsunder air blast loading
Lt Cdr Nagesh

Numerical Modelling Of Marine Screw Propeller With Comparison From Series Data
V. Anantha Subramanian and V.Amminikutty

Suppression Of Instability And Wall Turbulence Using A Compliant Surface
Cdr PS Josan, P. K. Sen, and S. V. Veeravalli

Cavitation Investigation and Nose Cone Optimisation of an Underwater Vehicle using Wind Tunnel
Lt Cdr A Saiju and Cmde N Banerjee

Performance Evaluation of Glass Epoxies - Coatings for Aggressive Environments
Lt Cdr S Sreekumar

An Inverse Design Approach for minimizing Wake at propeller plane using CFD
Lt Cdr R.Vijayakumar and V. Anantha Subramanian

BACK COVER, Vol. 1, No. 1, Mar 2005

Behaviour of a Ship in a Typhoon
Cdr PR Kulkarni

 ABSTRACT
Ship survivability against capsize in heavy seas is one of the areas of primary concern to the ship designer, ship operator and the ship regulator alike. Behaviour of a ship in rough weather depends on the magnitude and direction of wave excitation and ships own capability to resist such excitation. Most dangerous variety of wave excitation can be a group of steep, relatively long waves approaching the ship from the stern (following/quartering waves). Waves of this kind are known to incur significant reductions in roll restoring capability (i.e. the tendency of the ship to return to upright position), leading to very heavy rolling and ultimately capsize. Recent research on ship motion dynamics has lead to the discovery of the underlying causes of broaching, which occurs in quartering seas. This is a type of ship motion instability, which is manifested on the horizontal plane with a sudden divergence from the initial course (leading to a difficulty in course keeping), and may end up with a rapid ship capsize. The paper presents these aspects and properties of the following/quartering seas followed by a reconstruction of the sequence of events and circumstances that lead to a ship encountering three successive typhoons in the South China Sea. The ship was forced to maintain high speeds while encountering quartering seas for as long as 28 hours in an extremely adverse weather condition in the vicinity of a typhoon. This naturally resulted in the ship taking very heavy roll motion. The ship suffered a difficulty of steering control and ability to maintain course, a sure sign of occurrence of broaching, and it is a wonder that the ship did not capsize. On the return of the ship to its base port, while the associated structural damage sustained by the ship after encountering the typhoons was a cause of much debate, the underlying seakeeping aspects of the episode seem to be little understood. This paper presents ship-wave interaction under those conditions to explain the damages suffered.
 
Transient dynamic finite element analysis of plate panelsunder air blast loading
Lt Cdr Nagesh

ABSTRACT
The main objective of this work is correlation of simulated transient inelastic response using suitable material model and damage progression scheme with the experimental results of metallic plates both stiffened and unstiffened panels, subjected to blast loads. Such a comparison and validation will serve as guides to the numerical modeling and analysis of air blast loaded structure response phenomenon. The secondary objective is to provide data that could be used for checking the accuracy of a variety of calculation methods. The far field air blast phenomenon has been discussed and CHALMERS [1] methodology has been used to establish the blast load time history with specific explosive/charge parameters as inputs. The methodology to calculate the near field air blast load time history has also been discussed with reference to the work of JACINTO et.al.[19]. The time history of the blast loading as well as experimental / analytical response is obtained from the published works of OLSON [5] and Houlston et.al.[4]. A transient dynamic nonlinear (both geometric and material) analysis has been carried out to verify the numerical simulation with experimental and analytical results. Features of computational modeling and simulation of structures under impulsive loads have been discussed. The efficacy of the parametric numerical solution model has been established by comparison with experimental/analytical solution results from a variety of sources and different plate geometry / configuration. Elastic response of simply supported plate panels under low intensity shock loads have been compared with the experimental results of Houlston et.al.[4]. The stiffened panel response to shock has been compared with analytical results of Olson[5].
 
Numerical Modelling Of Marine Screw Propeller With Comparison From Series Data
V. Anantha Subramanian and V.Amminikutty

ABSTRACT
The propeller performance is usually predicted using open water model tests. In this paper an alternate approach has been attempted. The propeller variables are numerically modelled using a finite volume commercial code, FLUENT 6.0®. The case study considered here is the propeller designed for free running condition of a lube oil tanker. The propeller is modelled numerically using a three-dimensional unstructured mesh. In order to account for the propeller rotation, the model has been treated using the rotating reference frame capability in FLUENT. Two turbulence models namely, the standard k- and k- were used for simulation. The numerical models were run for different advance coefficients (J) to get the corresponding open water performance coefficients (KT, KQ, ). These results were then compared with
available series data for propeller performance characteristics. The approach and methodology for the numerical modelling along with comparisons are presented. The results are highly encouraging and the method is promising for evaluation of off-series designs.
 
Suppression Of Instability And Wall Turbulence Using A Compliant Surface
Cdr PS Josan, P. K. Sen, and S. V. Veeravalli

ABSTRACT
This paper discusses the role of hydrodynamic stability theory in understanding wall turbulence and its possible suppression by using compliant surfaces. Our work reveals that, in wall turbulent flows, there are three important ‘mode classes’; namely, the Tollmien-Schlichting (TS) mode class, the Static Divergence (SD) mode class, and the High-speed highly damped (HSHD) mode class. All these modes scale with inner wall variables (with r c close to 0.3) and so do the material properties of the compliant surface. The general thrust should be to replace TS modes by the HSHD stable modes. Outer modes (with r c close to 1.0) were also investigated and found to be damped.
 
Cavitation Investigation and Nose Cone Optimisation of an Underwater Vehicle using Wind Tunnel
Lt Cdr A Saiju and Cmde N Banerjee

ABSTRACT
Conventionally cavitation investigations of marine crafts and their propulsors are undertaken in the Cavitation Tunnel. However predictions of cavitation inception for underwater bodies can also be accurately carried out in the Wind Tunnels. Wind Tunnels are being used extensively for development of underwater vehicles especially torpedoes and underwater launched missiles for studying pressure distribution over the body and control surfaces, flow pattern on the body, vehicle-propulsor interaction studies, boundary layer and wake investigations etc. Tests in the Wind Tunnel are convenient, much faster, and far less expensive to conduct compared to those in the Towing Tanks and Cavitation Tunnels. This paper covers the cavitation studies carried out in the NSTL Wind Tunnel for optimisation of the nose profile of an underwater vehicle. The results obtained compare well with the cavitation investigation carried out in the Cavitation Tunnel on a similar body, which clearly establishes the usefulness of Wind tunnel tests in hydrodynamic research, especially in predicting inception of cavitation on submerged bodies.
 
Performance Evaluation of Glass Epoxies - Coatings for Aggressive Environments
Lt Cdr S Sreekumar

ABSTRACT
Corrosion protection of steel is a major design consideration for the use of steel for bridges, buildings, refineries, ships, etc. For steel in service, by far the most commonly used materials for corrosion protection are coatings. Without this protection, the steel would corrode to a stage with significant metal loss and possible reduction of structural integrity before reaching the design life of the structure. Protective coatings perform important functions like preventing the corrosion of the steel by isolating the steel from the environment, improving appearance etc. The paint industry has made significant progress in improving protective coatings. The prompt adoption and proper use of these improved materials can be expected of those responsible for the protection and appearance of costly structures especially in aggressive environments like splash zone, boot top areas of ships, tank linings etc,.Off late, extra corrosion resistance glass flake having high aspect ratio are becoming the integral part of many high performance coatings due to its chemical inertness, low water vapour permeability, superior cathodic disbandment properties and abrasion resistance. Solvent free or high solid glass reinforced coatings can provide an effective solution against the premature failure of coating systems even under the most demanding service environments like splash zone in offshore refineries, underwater immersion, internal tank linings involving harsh chemicals. The paper will elaborate on the benefits of glass flake reinforcement in high solid epoxy coatings and study the effect of increasing glass flakes loading on the performance of epoxypolyamine based coating system.
 
An Inverse Design Approach for minimizing Wake at propeller plane using CFD
Lt Cdr R.Vijayakumar and V. Anantha Subramanian

ABSTRACT
Knowledge of wake characteristic in the stern region is important for ensuring good propeller design and performance. CFD offers an effective technique of qualitatively (in terms of path of flow) as well as quantitative assessment of influence due to stern appendages such as bossings, struts supports and local shapes variations. This paper establishes the utility of CFD in the analysis of flow in the case of broad beamed vessels with characteristics cut stern shape. The analysis quantifies the effect of small changes in stern rake angles and offers an inverse design approach towards finalizing the stern shape. The method consists of solving the standard ke turbulent model of RANS equations in cell centered finite volume multi zone grid in the flow domain. This approach has been used in estimating the velocity at the propeller plane. The results have been compared with experimentally obtained values of nominal wake. The approach suggests that CFD can provide a cost effective quick assessment of flow and a reliable means of pre-empting adverse influences such as vibration and noise due to unfavorable wake in the stern region.
 
Copy of this volume can be purchased from the publishing office of the journal.