Cavitation is a complex phenomenon to measure, depending on site conditions in specific regions of the Earth, where there is water with various physical properties. The development of ship and propulsion technology is currently intended to further explore territorial waters that are difficult to explore. Climate differences affect the temperature and physical properties of water on Earth. This study aimed to determine the effect of cavitation related to the physical properties of water. Numerical predictions of a cavitating propeller in open water and uniform inflow are presented with computational fluid dynamics (CFD). Simulations were carried out using Ansys. Numerical simulation based on Reynolds-averaged Navier–Stokes equations for the conservative form and the Rayleigh–Plesset equation for the mass transfer cavitation model was conducted with turbulent closure of the fully turbulent K-epsilon (k-ε) model and shear stress transport (SST). The influence of temperature on cavitation extension was investigated between . The results obtained showed a trend of cavitation occurring more aggressively at higher water temperature than at lower temperature.
23 April 2018 in Journal of the Brazilian Society of Mechanical Sciences and Engineering
This work models the effect of an impact phenomenon—namely the interaction between seabed rock and a ship during its operations—on the ship structure. The collision between a tanker vessel with a conical rock is simulated, a scenario that is similar to the famous grounding of the Exxon Valdez oil tanker. The study uses finite element analysis to simulate numerical parameters that are related to structural response and the contours of the ship hull under impact loading. The traditional element-length-to-thickness (ELT) ratio of 10 is recommended in this work. ELT ratios in the range of 11 to 13 are shown to produce similar results in terms of internal energy, contact force, and structural acceleration. Additionally, the analysis time is reduced by approximately 20% for the recommended ELT ratio. This result is very helpful for researchers using finite element analysis to simulate ship accidents, since the mesh size or length of complex structures is used to maintain the efficiency and accuracy of the simulation results.
1 August 2017 in Latin American Journal of Solids and Structures
The impact phenomenon is one of many subjects that is interesting and has become an inseparable part of naval architecture and ocean engineering fields. Limitless possibilities in cause and scenario make the demand to understand the physical behavior of ship structures due to impact phenomenon is increasing. In present work, a series of virtual experiment is performed by finite element method to solve several defined collision scenarios. Two involved ships are classified as the striking ship which penetrates the target and struck ship as the target. Hull arrangement of the struck ship is considered as main parameter which single and double hull configurations are proposed to be assessed. An observation of the damage extent on struck ship subjected to collision loads are presented. The results indicate that the internal arrangement of the struck ship provides significant effects to resistance capability and structural failure after collision process. Finally, an analysis regarding the extent of the damage is summarized with a statistical calculation to provide distribution of crashworthiness criteria of the defined scenarios.
1 August 2017 in Latin American Journal of Solids and Structures
A series of analyses are carried out to predict the structural crashworthiness of a ship during a collision. The numerical configuration is verified by structural simulations based on a laboratory experiment wherein a penetration test is considered as the experimental reference. Comparative observations of structural behaviour are carefully conducted to ensure the reliability of the present method for conducting large-scale collisions. At this stage, the proper procedure and configuration for structural calculations subject to accidental loads are determined. The second stage addresses the calculations for various side collision scenarios. The simulations consider a double hull Ro-Ro passenger ship being struck at various locations, and the overall behaviour of the side hull along the longitudinal axis is observed. The main study considers the target location and striking speed to obtain adequate data related to crashworthiness criteria, i.e. the internal energy and extent of damage. Finally, the criteria of various scenarios are summarized. Further calculations comparing the results with a safety factor are presented together with a consideration of structural behaviour to estimate the safety limit within the confines of strait territory.