Japan Bulk Carrier Research Articles

Numerical Prediction of Propeller-Hull Interaction Characteristics Using RANS Method

Abstract The paper presents the results of computational evaluation of the hull-propeller interaction coefficients, also referred to propulsive coefficients, based on the unsteady RANS flow model. To obtain the propulsive coefficients, the ship resistance, the open-water characteristics of the propeller, and the flow past the hull with working propeller were computed. For numerical evaluation of propeller open-water characteristics, the rotating reference frame approach was used, while for self-propulsion simulation, the rigid body motion method was applied. The rotating propeller was modelled with the sliding mesh technique. The dynamic sinkage and trim of the vessel were considered. The free surface effects were included by employing the volume of fluid method (VOF) for multi-phase flows. The self-propulsion point was obtained by performing two runs at constant speed with different revolutions. The well-known Japan Bulk Carrier (JBC) test cases were used to verify and validate the accuracy of the case studies. The solver used in the study was the commercial package Star-CCM+ from SIEMENS.

Evaluation of hydrodynamic performance of pre-swirl and post-swirl ESDs for merchant ships by numerical towing tank procedure

Due to the EEDI regulation, recent merchant ships have strictly been required to achieve certain rate of energy saving, and thus equipment of energy saving devices (ESDs) has been quite popular. The purpose of this study is to investigate the working principle of pre and post swirl type ESDs via complementary use of experiment and viscous computational fluid dynamics (CFD).Three different hull forms (Japan Bulk Carrier: JBC, Duisburg Test Case container ship: DTC, and coastal tanker: COT) with three different ESDs are of the interest. Propeller open water, resistance and self propulsion tests are totally replaced by viscous CFD simulations, termed numerical towing tank procedure.For JBC, detailed investigations of self propulsion parameters, balance of kinetic energy flux, local flow and propeller loads clarify the working principle of its stern duct. For DTC, the present computations find out that vertical distribution of the twist angle of its rudder and the distance between propeller boss cap and the rudder bulb should be modified. For COT, the scale effect in axial and tangential components of its nominal and total wake are studied. In the meantime, the reason of deterioration/improvement in self propulsion coefficients by the pre swirl stator fins are identified.

A generic wake analysis tool and its application to the Japan Bulk Carrier test case

Economic pressures and regulatory obligations have brought about a great interest in improving ship propulsion efficiency. This has motivated and directed research to improve the hydrodynamic performance of a vessel thus seeking the development and generation of optimised designs. When analysing flow characteristics of a vessel, particular attention is given to analysing its wake field and stern flow characteristics. For the detailed analysis of the wake flow field, a Wake Analysis Tool (WAT) was developed within the programming environment of a commercial CAE tool. The WAT is based on a framework that enables easy interaction to an external CFD solver reading flow field properties from a generic csv file. The wake flow field is visualised and analysed in schematic form according to the standard and customized (i.e. the British Ship Research Association criteria) wake analyses. By coupling the CAE tool with a commercial flow solver, an example was given how to use the wake tool in a fully automated simulation process. Finally, the wake tool was used to analyse the nominal propeller wake flow of the Japan Bulk Carrier (JBC) thus showing how it can be efficiently applied to a set of numerical results.

Numerical simulation of the ship self-propulsion prediction using body force method and fully discretized propeller model

The study proposes a numerical solution for the self-propulsion prediction of the Japan Bulk Carrier (JBC) ship model based on two different approaches: the first is the body force method using an infinite-blade actuator disk, while the second is based on a 3-D fully discretized propeller using the sliding grid technique. The computations are performed for the ship with and without Energy Saving Device (ESD) by making use of the ISIS-CFD solver which is available in the commercial software Fine™/Marine provided by NUMECA. The solver is based on finite volume method to build the spatial discretization to solve the Reynolds-Averaged Navier-Stokes equation (RANSE) in a global approach. Closure to turbulence is made by making use of k-ω SST model for the actuator disk case and EASM for the propeller model case. A comprehensive investigation is brought into attention for the nominal wake and the effective wake flow, for clarifying and understanding the hull-propeller interaction. The computed results are compared to the experimental results presented in the Tokyo Workshop on the Naval Hydrodynamics 2015 and showed a reasonable agreement.

Vorticity structures and turbulence in the wake of full block ships

The objective of this paper is to study the physics of flow around the JBC (Japan Bulk Carrier) using different CFD methods and the open source toolkit (OpenFOAM). The computations were performed for a one-phase flow with a doubled body model using URANS k-ω SST, hybrid IDDES, and hybrid LeMoS turbulence models. A verification and validation procedure was performed for integral time-averaged forces acting on the ship and rotating propeller. The main point of this paper is the prediction of turbulent parameters in the wake. The turbulence kinetic energy was compared with measurements in different cross sections along the hull. Hybrid URANS/LES simulations have demonstrated superiority over URANS ones for the computation of the turbulence kinetic energy. The flow physics in the wake of full block ships, which can be reproduced only by scale resolving techniques, is discussed. Finally, the unsteady forces on a rotating propeller MP.687 working behind the JBC hull are determined.