[논문]A numerical simulation for reduction of rudder cavitation with gap flow blocking bars

Oh, Jung-Keun; Lee, Seung-Hee; Kim, Sang-Hyun; Seo, Dae-Won

doi:10.3744/jnaoe.2012.4.2.071

[국내논문] A numerical simulation for reduction of rudder cavitation with gap flow blocking bars 원문보기

International journal of naval architecture and ocean engineering, v.4 no.2, 2012년, pp.71 - 82

Oh, Jung-Keun (Jungseok Research Institute of International Logistics and Trade, Inha University) , Lee, Seung-Hee (Department of Naval Architecture & Ocean Engineering, Inha University) , Kim, Sang-Hyun (Department of Naval Architecture & Ocean Engineering, Inha University) , Seo, Dae-Won (Jungseok Research Institute of International Logistics and Trade, Inha University)

Abstract ▼ AI-Helper

In recent practices, a half circular prismatic bar protruding beyond the concave surface of the horn facing the gap has been formed along the centerplane of a rudder to lessen the gap flow between the horn and the movable portion of the rudder system. If a flow through the gap of a rudder is reduced considerably through this approach, previous numerical studies indicate that not only the gap flow but also the rudder cavitation can be noticeably diminished. In the present study, numerical simulations on two-dimensional rudder sections were performed to show that the blocking ability of the single centre bar can be improved by the proper choice of sectional shape. Moreover, a pair of blocking bars attached symmetric to the centerplane on the opposite convex surface of the movable portion is suggested in the study as well, to circumvent the difficulties arising from the practical application of the single centre bars. The bars are placed near the outer edges of the gap easily accessible at the maximum rudder angle to allow simple installation of the device during a maintenance period of a ship. It is found that the pair of blocking bars further improves the blocking effects and application to a practical three-dimensional rudder also backs up the fact.

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제안 방법

In the initial stage, two-dimensional computations were performed to investigate the influence of cross sectional shapes upon the effectiveness of the blocking bars. Two sections were selected at the horn and pintle of the rudder model for 2-dimensional analyses and Fig.
After that, computations were carried out to study the flow characteristics around the three-dimensional rudder model equipped with the pair of blocking bars found to be the most effective among the two-dimensional models tested and the results were compared with the case without any gap flow blocking device. The numerical grid for the three-dimensional horn-type rudder system is shown in Fig.
Numerical computations were carried out at the rudder angle of 3°, as in two-dimensional computations, to confirm the capability of the bars in blocking the gap flow.
A pair of half-circular cylindrical bars fillet jointed symmetrically to the centerplane was chosen as the best pick for a gap flow blocking device and was attached to a practical three-dimensional horn type rudder to demonstrate its usefulness in blocking the gap flow and the consequential rudder cavitation. The symmetric blocking bars are convenient to install and maintain and can be mounted easily on the rudder of a ship already in operation.

대상 데이터

For numerical study of the performance of the devices for blocking gap flow, a scale model of a horn-type rudder of an 8,000 TEU class container ship with a design speed of 25 knots was selected as shown in Fig. 1. The scale ratio of the model to the original rudder was chosen to be 1/10 and the effects of the wake behind a propeller and hull were not considered.

이론/모형

3 has been used for numerical computations, which employs a cell-centered finite-volume method along with a linear reconstruction scheme in order to use computational cells of arbitrary polyhedral shapes. A SIMPLE type segregated algorithm was chosen for the velocity-pressure coupling. The discretization schemes for pressure and momentum were 2nd order accurate and the turbulent kinetic energy and dissipation rate were discretized by QUICK and 1st order upwind scheme to include the complex flow near the gap in the 2D calculations.

참고문헌 (11)

Boo, G.T., Song, I.H. and Shin, S.C., 2004. Numerical Simulation for the Rudder in order to Control the Cavitation Phenomena. Journal of Ship and Ocean Technology, 8(1), pp.42-50.
Kim, M.C., Lee, U.S. and Byun, T.Y., 2008. Study on Optimization of Anti-erosion Rudder Section of Large Container Ship by Genetic Algorithm. Journal of the Society of Naval Architects of Korea, 45(3), pp.403-410.

원문보기 상세보기
Paik, B.G., Kim, K.Y., Ahn, J.W., Kim, Y.S., Kim, S.P. and Park, J.J., 2008. Experimental study on the gap entrance profile affecting rudder gap cavitation. Ocean Engineering, 35(1), pp.139-149.

상세보기
Park, K.R and Lee, Y.G., 2010. A Study on the Rudder Shapes for the Suppression of Cavitation around a Horn-type Rudder. Journal of the Society of Naval Architects of Korea, 47(4), pp.553-564.

원문보기 상세보기
Rhee, S.H., Lee, C.M., Lee, H.B. and Oh, J., 2010. Rudder Gap Cavitation: Fundamental Understanding and Its Suppression Devices. International Journal of Heat and Fluid Flow, 31(4), pp.640-650.

상세보기
Rhee, S.H. and Kim, H., 2008. A Suggestion of Gap Flow Control Devices for the Suppression of Rudder Cavitation. Journal of Marine Science and Technology, 13(4), pp. 356-370.

상세보기
Singhal, A.K., Athavale, M.M., Li, H. and Jiang, Y., 2002. Mathematical bases and validation of the full cavitation model. Journal of Fluid Engineering, 124(3), pp.167-264.
Shen, Y.T., Jiang, C.W. and Remmers, K.D., 1997. A Twisted Rudder for Reduced Cavitation. J. Ship Research, 41(4), pp. 260-272.
Seo, D.W., Lee, S.H., Oh, J.K. and Kim, H., 2010. A Numerical Study for the Efficacy of Flow Injection on the Diminution of Rudder Cavitation. International Journal of Naval Architecture and Ocean Engineering, 2(2) , pp.104-111.

원문보기 상세보기
Seo, D.W., Lee, S.H., Kim. S.H. and Oh, J.K., 2012. Practically applicable devices for blocking the gap flow of a horn rudder to reduce rudder cavitation and their verification through numerical simulations. J Mar Sci Technol, 17(1) , pp.18-29.

상세보기
Guo, B., Langrish, T.A.G. and Fletcher, D.F., 2001. Simulation of turbulent swirl flow in an axisymmetric sudden expansion. AIAA journal, 39(1). pp.96-102.

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