Ultimate Strength of Unstiffened and Stiffened Plates subject to Combined In-Plane Compression and Lateral Pressure
- K. Doshi and S. Vhanmane
Abstract :Plating used for fabrication and construction of ship structures is subject to initial imperfections induced due to welding processes. The strength of the plating is evidently subject to degradation due to imperfections in presence of compressive axial loads. Lateral pressure also influences the strength of the plating in presence of compressive loads. The present work attempts to study this influence on the ultimate strength of unstiffened and stiffened plates with initial imperfections subject to compressive loads. Representative plating from oil tankers and bulk carrier vessels was analyzed using non-linear finite element analyses considering the above mentioned load configurations. Results from the analyses demonstrate that the presence of lateral pressure further degrades the compressive strength of the ship plating. The present analyses may prove to be useful to develop a tool which can be used by the ship designers to evaluate structural safety in a rational manner.
Parametric Bulbous Bow Design for the minimization of Ship Resistance by using CFD
- Deddy Chrismianto and Dong-Joon Kim
The parametric modeling plays an important role for the optimization aim in the Computational Fluid Dynamic (CFD) analysis. But in fact, it is so hard to create a parametric modeling for some spline shapes, such as a bulbous bow. In this study, the cubic Bezier curve and curve-plane intersection methods are applied to generate the parametric design of a bulbous bow in a solid modeling with taking into account 4(four) input parameters. For this reason, a scripting of the Application Program Interface (API)is also required to develop some programming codes under the ANSYS Design Modeler. An instance of the application of a ship resistance minimization by using CFD was made to show that the proposed method can be implemented properly. The parametric design of a bulbous bow of the container ship (KCS type) was chosen to be modified. First, this ship with using an original bulbous bow shape must be analyzed using CFD, in which this analysis shows that the computational result was close to the experiment result. Then, the optimization method was implemented to find the optimal bulbous bow.
Hydrodynamic Performance Optimization of a Wake-Adapted Propeller
- Naga Venkata Rakesh N. and V. Anantha Subramanian
Abstract: The study demonstrates the design of a wake adapted marine propeller employing the Vortex Lattice Method (VLM) applied for the case of a highly loaded propeller for the design speed. The method obtains nominal wake field and resistance data using a commercial RANSE package and starting from an initial propeller design improves it for optimum efficiency. The initial geometry of the propeller based on optimum circulation distribution is adapted to the flow conditions (wake) for the given vessel through blade alignment and propeller wake alignment. By this method the loss in terms of torque power is minimized for a given thrust requirement, thus improving the propeller efficiency. The method generates optimized propeller blade geometry. The self-propulsion condition is simulated using CFD, and the rigid body motion approach to analyse the propeller performance characteristics. The scheme represents advancement as a numerical tool towards propeller design and analysis.
Comparative Study of Container Stowage and Securing Arrangements Using Various Classification Societies Rules / Guidelines
S. Awasare and K. Doshi
One of the important aspects of container ship safety is the stowage and securing of containers onboard. It is imperative to ensure that the containers are properly secured using appropriate lashing components and equipment. For this purpose the inertial forces arising due to the ship motions as well as forces due to the wind are mainly considered for evaluation. In the current work, a comparison of various parameters for a given stack configuration viz., the imposed acceleration, inertial and wind forces on containers, racking forces on the end and side walls of the containers, the vertical tensile/compressive forces on the corner post castings, forces in the lashing rods etc as obtained from various classification societies rules/guidelines is done. The evaluations are performed on a sample stack configuration considering the utilization of lashing equipment. Motion analysis on a sample vessel also has been performed using hydrodynamics software in order to assess the validity of the acceleration values as per class rule formulations to calculate forces in three directions. The study provides a useful insight into the various parameters which are needed to correctly determine the forces subjected on containers as well as on the lashing components.