Volume 2 Issue 3
Authors: Lidui Wei; Haijun Wei; Yunlong Sun; Liwei Liu
Abstract: Based on the whole flexible engine block and the flexible crankshaft reduced by CMS method, considering mass-conserving boundary conditions, the average flow Reynolds equation and Greenwood/Tripp asperity contact theory, an EHD mixed-lubrication model of the main bearings for the diesel engine is developed and researched with finite volume method and finite element method. The results show that under the whole flexible block model, maximum oil film pressure and maximum peak contact pressure decrease, while minimum oil film thickness increases. Oil flow over edge decreases, and friction loss also decreases. Therefore, coordination deformation ability of whole engine block is favourable to mean load. In the whole block model, friction contact happens in both upper shell and lower shell positions. So, wearing resistance of both upper and lower shells must be enhanced simultaneously. Therefore, it is very important to predict the mixed-lubrication performance of main bearings accurately, based on the whole flexible engine block.
Keywords: Flexible Whole Engine Block Model; Crankshaft; Main Bearing; Elastohydrodynamic Mixed-Lubrication
Numerical Computation of Wave Resistance Around Wigely Hull Using Computational Fluid Dynamics Tools
Authors: Salina Aktar; Goutam Kumar Saha; Md. Abdul Alim
Abstract: The practical application of the Computational Fluid Dynamics (CFD), for predicting the flow pattern around ship hull has made much progress over the last decade. Today, several of the CFD tools play an important role in the ship hull form design. CFD has been used for analysis of ship resistance, sea-keeping, manoeuvering and investigating its variation when changing the ship hull form due to varying its parameters, which represents a very important task in the principal and final design stages. Resistance analysis based on CFD (Computational Fluid Dynamics) simulation has become a decisive factor in the development of new, economically efficient and environmentally friendly ship hull forms. Three-dimensional finite volume method (FVM) based on Reynolds Averaged Navier-Stokes equations (RANS) has been used to simulate incompressible flow around two conventional models namely Wigely parabolic hull in steady-state condition. The numerical solutions of the governing equations have been obtained using commercial CFD software package FLUENT 6.3.26. Model tests conducted with these two models are simulated to measure various types of resistance coefficient at different Froude numbers. It is instructive to visualize the free surface wave generated due to the motion of the hull. This was created using a derived part within FLUENT .The numerical results in terms of various resistance coefficients for different Froude numbers have been shown graphically or in the tabular form. We have also compared wave drag coefficient with another numerical result named Boundary Element Method (BEM) .The agreement between the numerical results and the experimental indicates that the implemented code is able to reproduce correctly the free-surface elevation around the Wigely parabolic hull. The computed results show good agreement with the experimental measurement and also with BEM.
Keywords: Resistance Co-efficient; Turbulent Model; Froude Number; Pressure Co-efficient; RANS Equation; Wave Resistance Co-efficient
Authors: Hidemi Mutsuda; Akihiro Ishida; Yasuaki Doi; Suandar Baso
Abstract: In recent years, to achieve a goal of reducing greenhouse gas, a fishing boat which is very economical on gas should be needed. Over the last two decades, improvements of bow part in fishing boat have been researched to reduce water resistance. Moreover, stern End Bulb research took place mostly in Japan. No one finds universal knowledge for reducing drag resistance because many fishing boats run with individual catching styles for each fish. It is also difficult to appropriate some techniques in cruise ship and tanker for fishing boat. In this study, to reduce drag resistance, improvement of body line and addition product at stern part were examined. All of the cases proposed in this study could reduce water resistance. The maximum reduction rate was around 15 to 20% comparing with the basic form (original case). Some useful improvements were found based on Computational Fluid Dynamics (CFD) works and flow visualization by Particle Image velocimetry (PIV) technique.
Keywords: Fishing boat; Stern; Resistance reduction; CFD