научная статья по теме A STUDY ON HIGH LIFT RUDDERS WITH WEDGE TAIL AND END PLATES Машиностроение

Текст научной статьи на тему «A STUDY ON HIGH LIFT RUDDERS WITH WEDGE TAIL AND END PLATES»

cyAOCÏPOErlÈE 6'2014

APHydro2014

CONCLUSIONS

A new air circulating tank (ACT) was developed in the present study.

Following conclusions have been obtained.

1) A rectangular ACT has superior efficiency to reduce ship resistance in even trim condition. At low Froude number below 0.15, the efficiency of it is 70% of reduction ratio of wetted surface by ACT.

2) A new ACT which keeps smaller volume of air than the ACT volume is developed to avoid air escaping from it at trimmed conditions or in ship motions in waves. Convex flow guides are attached at fore and aft part of ACT to make water flow smoothly.

3) CFD simulations show thaL the new ACT makes inside air circulate naturally and reduce generation of waves on the free surface between air and bottom water flow.

4) It was experimentally confirmed that the new ACT can reduce the

resistance of a ship in trimmed condition. Some problem at large stern trim should be solved in future.

REFERENCES

1) Y. Gorbachev and E. Amromin (2012). "Ship Drag Reduction by Hull Ventilation from Lavcl to Near Future: Challegcs and Successes" ATMA.

2) T. Sato, T. Nakata, M. Takeshita, Y. Tsuchiya and H. Miyata (1997). "Experimental Study on Friction Reduction of a Model Ship by Air Lubrication" Jour. Of The Society of Naval Architccts of Japan, Vol. 182, pp 121-128.

3) S. Mizokami, C. Kawakita, Y. Kodan, S. Takao, S. Iligasa and R. Shigenaga (2011). "Development of Air lubrication system and verification by the full scale ship test". Jour, of the Japan Society of Naval Architects and Ocean Engineers, Vol. 12, pp 69-77.

A Study on High Lift Rudders with Wedge Tail and End Plates

Trieu Van Nguyen, Yoshiho Ikeda Department of Marine System Engineering, Graduate School of Engineering, Osaka Prefecture University

Sakai City, Osaka Prefecture, Japan dxl 02001 @edu.osakafu-u.ac.jp

ABSTRACT

In this study, higher lift marine rudders with wedge tail and end plates are developed by using a commercial code of Computational Fluid Dynamics (CFD). The numerical results show that, a small wedge tail of 2.5% chord length increases the maximum lift force of the rudder by 16%. Moreover, the small wedge tail and two end plates attached at top and bottom of the rudder give 25% higher maximum lift than that of the original semi-balanced rudder. Increase of drag force due to the wedge and end plates arc numerically investigated and discussed.

KEY WORDS: Rudder, lift, drag, wedge tail, end plates, ship maneuvering, CFD.

INTRODUCTION

As well known, marine rudders play an important role in ship maneuvering and navigation. Especially, very large and low speed vessels require a very large rudder to obtain a high lift force. However, the size of a rudder is usually limited by the ship stern configuration. Therefore, it is necessary to develop a new type of rudder with higher lift force and small drag.

For better maneuverability or a smaller rudder of ships, rudders with higher lift and smaller drag have been sought. The ways to increase lift force of lift surfaces were comprehensively introduced in the books written by llocmcr and Borst (1975), Molland and Turnock (2007). These books introduced that a tail wedge foil increases its maximum lift by about 20-30% but is accompanied by higher drag.

Recently, Nguyen and Ikeda (2014) numerically studied the hydrodynamic characteristics of wcdgc-tail rudder sections with high lift force of a simple rectangular rudder, The calculated results showed that a smaller wedge tail of the rudder provides better hydrodynamic performances than the large wedge tail because of higher lift but small drag.

This paper presents a development of a newly semi-balanced rudder with a wedge and endplates with higher lift but small drag by using CFD. For the calculation a CFD commercial code, ANSYS FLUENT is used.

RUDDER GEOMETRY

7.2

I

\ V

■i

CM

1 0

15 3

Tabic 1. Rudder model's parameters

Parameter Value Unit

Rudder height 24.4 cm

Chord length (Top) 17.2 cm

Chord length (Bottom) 15.3 cm

Total rudder's area 384.8 cm'

Aspcct ratio 1.92 -

METHODOLOGY FOR DEVELOPMENT High Lift Rudder Section

A high lift rudder scction with a wedge tail can be seat as in Fig. 2.

4

The geometry of the original rudder, a semi-balanced rudder, is shown as in Fig. I. 'fhe main parameters of the rudders are listed in fable 1.

Fig. 2. Rudder cross section with a wedge tail (tmax: maximum thickness, c: chord length, h: wedge thickncss)

APHydro2014

СУДОСТРОЕНИЕ 6'2014

СУДОСТРОЕНИЕ 6'2Q14

APHydro2Q14

APHydro2014

cyflOCTPOEHMi 6'2014

Measurement of Sloshing Flow Using Particle Image Velocimetry

Jieung Kim*, Jae-Han Kim**, Sang-Yeob Kim* and Yonghwan Kim*' ^Department of Naval Architecture and Ocean Engineering, Seoul National Univ ersity

Seoul, Korea

**Daewoo Shipbuilding & Marine Engineering Co. Ltd Seoul, Korea tyhwankim@snu.ac.kr

ABSTRACT

In this study, a particle image velocimetry(PIV) technique is used for measuring the velocity vectors of sloshing flow, and the measured velocity fields are compared with those of an analytic solution. For this PTV experiment, a two-dimensional rectangular tank and two high speed cameras are installed on motion platform. Various image capturing methods and filtering sehemes are used for velocity vector analysis. The velocity vectors of fluid flow are compared between experimental data and analytic solutions.

KEY WORDS: PIV, Sloshing, Standing wave, flow measurement

INTRODUCTION

As sloshing analysis is an essential element in LNG ship cargo design, fluid flows in partially filled tank have been studied actively based on experimental, semi-analytic and numerical methods. Because of the

experimental, semi-analytic and numerical methods. Because of the strong non-linearity of physical phenomena, sloshing problems were preferably studied by experimental way rather than numerical method. Particularly, sloshing-induced impact pressure has been the main interest for the structural assessment of LNG CCS(cargo containment system). Recently, velocity measurement in sloshing flow is of interest, since people are getting interested in the correlation between velocity and dynamic pressure. H'or instant, Gavory (2005) suggested to use a PIV technique for the velocity measurement of violent sloshing flow. There are a few existing studies adopted PIV technique in sloshing experiment. Lugni el al. (2006) measured pressure and velocity in flip through of sloshing using PIV. Doh et al. (2011) used PTV for evaluating the occurrence of sloshing. Ahn et al. (2012) measured oscillating characteristics of pressure and velocity using PIV in Ihe case of trapped air at the tank roof. Likewise there have been various research on PIV applied on sloshing, but it is hard to find three-dimensional PTV measurements for sloshing flow. Recently, PIV system has been equipped in SNU sloshing tank for measuring three-dimensional sloshing flows.

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