 |
| |
CURRENT ISSUE
Vol. 6, No. 2; July 2010
PREVIOUS ISSUES
Vol. 6, No. 1; January 2010
Vol. 5, No. 2; July 2009
Vol. 5, No. 1; January 2009
Vol. 4, No. 2; July 2008
Vol. 4, No. 1; January 2008
Vol. 3, No. 2; July 2007
Vol. 3, No. 1; January 2007
Vol. 2, No. 2; July 2006
Vol. 2, No. 1, January 2006
Vol. 1, No. 1. March 2005 |
| |
|
|
Stability of Fluid Flow Through a Compliant Pipe With Interface Interventions
PK Sen and Munendra Kumar
Stress Analysis of Cylindrical Panels with Different Boundary Conditions Using Extended Kantorovich Method
Rahbar Ranji A and Rostami Hoseynabadi H
Dezincification of Brass in Cochin Estuary, India
A. Mathiazhagan, Rani Joseph, K.P.Narayanan & P.Seralathan
Simulation of Variety of Waves in a Physical Wave Tank
Dr. Ramakrishnan Balaji, Sannasiraj S.A and Sundar V.
Thrust Allocation Logic of Dynamically Positioned Offshore Vessel
Jeyasenthil R and Dasgupta J
A method for analysis of costs and benefits of antifouling systems applied on ship’s hull
Sangeeta Sonak, Asha Giriyan and Prajwala Pangam
BACK COVER, Vol. 6, No. 1, January 2010
Stability of Fluid Flow Through a Compliant Pipe With Interface Interventions
PK Sen and Munendra Kumar
ABSTRACT
The present paper discusses the hydrodynamic stability of flexible pipe flow, considering a viscoelastic pipe, with an outer rigid shroud, and with Hagen-Poiseuille flow through pipe, with interface interventions. There are two types of interface interventions considered in this paper. The first is an interface plate which allows only normal motion to pass through to the solid-side. The second is an interface sheet pasted to the solid-side. This sheet is held by light springs at the ends, and the springs are so stretched in tension that the sheet does not allow mean tangential displacement of the solid-side. Yet, since the springs are light, perturbation and tangential displacements are actually passed on to the solid-side. The neutral stability curves for different values of the compliance parameter  and of the solid to fluid viscosity ratio mr = ms/mf are examined, where ms is the solid-side viscosity, and mf is the fluid-side viscosity and r , V and G are respectively the density of fluid, maximum velocity of fluid and shear modulus of f the visco-elastic material. The effect of displacement stress term is studied for different types of modes. The normal (N) compliance modes are more unstable and are subsequently different from the normal plus tangential (N+T) compliance modes. It is also found that wall dissipation tends to damp most classes of modes.
Keywords: Pipe flow stability, Normal and tangential compliance, Neutral curves, Interface interventions, Visco-elastic pipe, Static divergence modes.
Stress Analysis of Cylindrical Panels with Different Boundary Conditions Using Extended Kantorovich Method
Rahbar Ranji A and Rostami Hoseynabadi H
ABSTRACT
A semi-Analytical approach for the stress analysis of thin cylindrical panels under general loading is presented. Different combinations of boundary conditions i.e. simply supported and clamped are considered. The formulation is based on extended Kantorovich method (EKM). Application of EKM to the system of partial differential equations reduces the governing equations of problem to a double set of ordinary differential equations in the variables x and q. These sets of equations were then solved in an iterative manner until convergence was achieved. In any iteration, exact closed form solutions are obtained for ODE systems. Rapid convergence and high accuracy of method are examined through a comparison with exact solutions (where available) and with finite element analyses. Both deflection and stresses at various points show good agreements.
Keywords: Extended Kantorovich method; Cylindrical Panel; Stress Analysis.
Dezincification of Brass in Cochin Estuary, India
A. Mathiazhagan, Rani Joseph, K.P.Narayanan & P.Seralathan
ABSTRACT
Corrosion characteristics of brass panels were investigated in estuarine water, Cochin at an interval of 1, 3, 6, 9 and 12 months. The weight gains and corrosion rates were measured by gravimetrically and open circuit potentials were determined by digital multimeter with a saturated calomel electrode (SCE). The concentrations of Cu2+ and Zn2+ ions in solution, produced by the corrosion of brass were determined by atomic absorption spectrometry. Morphology of corroded surfaces, with and without the corrosion products, was analyzed by scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) was used for the identification of the corrosion products and X-ray diffraction (XRD) was used for identification of the crystalline corrosion products. The results of the study were discussed in the light of the estuarine water characteristics.
Keywords: Brass, corrosion, estuary, Cochin
Simulation of Variety of Waves in a Physical Wave Tank
Dr. Ramakrishnan Balaji, Sannasiraj S.A and Sundar V.
ABSTRACT
A variety of water waves have been simulated in a physical wave tank facility and their characteristics were investigated. Wave groups, breaking waves and nonlinear waves are simulated and analysed in the present study. The wave group and breaking wave time histories were theoretically estimated and then converted to first order physical wave tank paddle driving signals. The various types of measured wave elevation time histories were processed using different analyzing techniques to understand their characteristics. The details of the test facility, instrumentation, testing conditions and the analysis are presented in this paper.
Keywords: Wave groups, breaking waves, nonlinear waves, physical wave tank and phase portraits.
Thrust Allocation Logic of Dynamically Positioned Offshore Vessel
Jeyasenthil R and Dasgupta J
ABSTRACT
In Dynamic Positioning systems, “Thrust Allocation” is the problem of determining the thrust and the direction of each of the “n” thrusters of an over-actuated offshore vessel from the desired forces and moment derived in the control law. This is formulated as a non-linear optimization problem, where the objective is to minimize the use of control effort subject to the constraints such as actuator rate and power constraints as well as other operational constraints. This paper presents the thrust allocation method for vessels equipped with azimuth thrusters, where the nonlinear constrained allocation problem has been solved by Sequential Quadratic Programming (SQP) method. Simulation results are presented for a semi-submersible where the constraint compliance has been satisfactorily achieved.
Keywords: Thrust Allocation; Azimuth Thrusters; Dynamic Positioning; Sequential Quadratic programming method, nonlinear constrained optimization.
A method for analysis of costs and benefits of antifouling systems applied on ship’s hull
Sangeeta Sonak, Asha Giriyan and Prajwala Pangam
ABSTRACT
Ship’s hull remain submerged in sea and hence attract growth of fouling organisms. Antifouling paints are applied on the hull of the ships and boats to control attachment of these marine organisms. Since the mid 1960s, tributyltin based antifouling paints are used against fouling organisms. They established themselves as antifoulants of choice. However, TBT is described as the most toxic substance ever introduced in the marine environment. Therefore, Convention to Control the use of Harmful Antifouling Systems on Ships (AFS Convention) was adopted by IMO in 2001. The convention prohibits use of harmful organotins in anti-fouling paints used on ships. While the application of organotin-based antifouling paints is prohibited on ship’s hull, there are no safe and effective alternatives available for control of growth of fouling organisms. Therefore, this paper examines the cost of fouling to the shipping industry and points out to an urgent need to focus and invest in research on antifouling technologies. The paper presents a methodology to calculate the efficiency of antifouling systems based on an assessment of their costs and benefits to the ships. Using this method, costs and benefits of an individual antifouling system can be evaluated.
Keywords: Fouling, antifouling system, AFS Convention, cost and benefit, method
|
