This paper reports the development of a new body-force model for the rotating propeller within viscous flow code and its application to uniform flow and propeller advancing with the angle of attack. A simplified quasi-steady blade element theory with the infinite-bladed propeller model (time averaged propeller induced velocity field) is coupled with the Reynolds averaged Navier-Stokes (RANS) code to determine the thrust and the torque distributions. The present effort aims to reduce the computational effort while keeping the effect of ship with motion in quasi-steady manner for propeller. The solid-surface effect on the propeller loading and power is also studied. Open-water validation simulations are done for the Methodical-AU type fixed-pitch propeller. Reported results show fair predictive agreement between the new body-force model and the experimental data.
Computational Fluid Dynamics (CFD) technique for ship hydrodynamics has been well developed with advanced capabilities for resistance and propulsion, seakeeping, and maneuvering. The Authors’ laboratory (Laboratory 3 of Department of Naval Architecture and Ocean Engineering in Osaka University) specializes in resistance and propulsion field and has carried out several simulations based on the CFD code in non-inertial ship-fixed coordinates system. The purpose of this research is to transform the present computation code to the one in inertial coordinate and to investigate the flow field around the Wigley hull for several motions up to three degrees of freedom (3 DOF). The transformed code is simulated on the flat plate initially and the nature of the flow field is investigated and confirmed with the hydrodynamics theory. Then, the wigley hull motions are simulated in several ways such as; uniform motion, pure yaw and circular motion test. The features of the flow field and hydrodynamic forces acting on the hull are discussed based on the computed results. Finally, the propeller effect is implemented behind the wigley hull using the body-force concept by the quasi-steady infinite bladed Blade Element Theory and a propulsion characteristic is observed. The transformed computation code in inertial coordinate is found to be much easier to simulate the different kinds of maneuvering motions compared to the code in non-inertial system and this paper covers the detailed transformation steps and the discussions on the computation results of different motions.
The viscous flow simulation is carried out around the KVLCC2 tanker model by the simple and effective way using a new body-force distribution model for the propeller-hull and propeller-hull-rudder interaction. The simple body-force model based on quasi-steady blade element theory is coupled with the Reynolds averaged Navier-Stokes (RANS) code CFDSHIP-IOWA. The captive tests in the trimmed condition and even-keel condition are computed with rudder and without rudder. The computational condition is set up according to the experiments in Osaka University towing tank and the output flow fields are analyzed in details especially in the wake field around the rudder and propeller. The computational results are not only validated with the experiments but also compared with the real propeller computation and other body-force models in order to find out the advantage of the current method. Summarizing the results, the present study could provide the complicated wake field patterns behind the tanker hull form which are as close as the experiment by simply using the new body-force distribution model and the current method can predict the wake field superior to the other body-force models.
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