港航外文翻譯--從一個船閘到另一個船閘（原文）

1、 885From water entry to lock entry Xue-nong Chen1* 1Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology P.O.Box 3640, D-76021 Karlsruhe, Germany * E-mail: xue-nong.chen@kit.edu ABSTRACT :

2、 In this paper, the ship lock entry problem is studied, which is physically similar to, but numerically different from, the water entry problem simulated by the author 25 years ago under the instruction of Prof. He. A

3、 one- dimensional unsteady hydraulic narrow-channel model for the flow coupled to the ship's motion in surge, heave and pitch is formulated and numerically implemented. The calculated ship motions were validated b

4、y comparison with model experiments carried out in the Duisburg shallow water tank. The viscous effects are further taken into account in order to investigate the scale effect in the experimental modeling in a framewo

5、rk of new lock project of Panama Canal. Thus, the experimentally validated model is applied to optimize the lock entry time by changing the trust course in the full-scale case. KEY WORDS: Water entry; ship lock entr

6、y; free surface motion; ship motion; dynamic fluid-rigid body coupling. 1 INTRODUCTION Twenty five years ago, under the instruction of Professor Yousheng He, the author was finished with his master-degree thesis [1]

7、on the topic of 3-D numerical simulation of water entry problem. A key nature of this problem is a strong interaction between rigid body and free surface motions. As a rigid body (a missile) crashes into water, it ma

8、kes a remarkable free surface motion and it experiences by reaction a huge momentum that brakes its forward motion or alters its motion direction in case of asymmetrical entry. Today, in the Professor He’s Eightieth

9、Birthday Symposium, the author would like to introduce another problem, which comes from a totally different application field, but has a very similar physical nature to the water entry problem, namely, ship lock en

10、try. As the ship begins to enter the lock, because of the sudden narrowness or shallowness of the lock, the ship pushes a mass of water ahead, so that a bore is generated in the lock. By the way of reaction the ship s

11、uffers an impact, decreasing its forward speed enormously and causing remarkable pitch and heave motions. It has really the same nature as the water entry problem, where again the interaction between rigid body and f

12、ree surface is in the foreground. In this paper the problem of ship motions into or within a very narrow lock, not only restricted by the lock entry, is studied with special attention to the interaction between ship m

13、otion and ship waves and moreover to the viscous effects of flow blockage and friction. A one-dimensional unsteady hydraulic narrow-channel model for the flow coupled to the ship's motion in surge, heave and pitc

14、h is formulated and numerically implemented. Although the first numerical example of ship entry into a lock was validated by model experiments carried out in the Duisburg shallow tank [2], by applying a primitive tri

15、al and error viscous coefficient [3], a new physical viscous model is needed and developed in this paper. The accurate prediction of such motions, especially the ship entry speed and time, is of great practical relev

16、ance, not only from the technical point of view, but also from the economical point of view. However, it is very difficult to extend the model scale experimental results to the real scale ones under the Froude simila

17、rity, because the fluid viscosity plays an important role in this unsteady flow and can not be fully taken into account simply by an addition of an overall Reynolds dependent viscous resistance to the pressure one. 8

18、87local friction on the canal side-walls and the ship-hull surface. It has a dominant effect, but the modeling that was applied in the past [3], was quite primitive and its value was determined by trial and error in t

19、he numerical calculation. The improvement of this local friction model is the main effort of this paper, which will be described in the next section. The α2-term represents a small viscous wave damping and may be ne

20、glected. By virtue of symmetry only three degrees of freedom (surge, heave and pitch) are considered. The relevant hydrodynamic forces Fx, Fz and the moment My due to the pressure (6) acting on the ship are expresse

21、d in detail in [3]. The rigid body dynamic equation of the ship surge motion reads 22 ddx f m F T R tξ = + ? , (7) where T is the propeller thrust and Rf the hull frictional resista

22、nce. In current calculations the thrust T, as a function of time, is assumed to be known. However, it is a function to be optimized, e.g. for a minimal entry time. A local frictional resistance model is developed base

23、d on the Prandtl turbulent velocity profile. This is an essential part in the viscous model and a new development in comparison with the viscous resistance correlation used in [3], i.e. the ITTC-1957 formula w

24、ith some empirical velocity-increase correction due to the restricted water effect. The rigid body dynamic equations of the ship heave and pitch motions read -22 ddzs m F t = , 2' ' ' 2 d , dy y G y G J

25、 M tθ =(8) By substituting the pressure integral of Fz and My’G into above equations a compact form of heave and pitch equations can be rendered as ( )2sink 2 d d ( ) 0 d d s w w s s m g A s M I t t α ρ θ + + + + =(9)

26、( )2trim 2 d d ( ) 0 d d t w w J g I M s I t tθ θ α ρ θ + + + + = (10) with ' ' y y G J J =for simplicity, s α and t α as empirical damping coefficients for sinkage and trim, respectively

27、, the static water-plane integrals /2/2 ( ')d 'lwl A b x x? = ∫ , /2/2 ( ' ' ) ( ')d 'lw GlM x x b x x? = ? ∫ , /2 2/2 ( ' ' ) ( ')d 'lw GlI x x b x x? = ? ∫ , and dynamic auxilia

28、ry integrals /2sink/2 ( ) ( , ) ( ')d ',llI t x t b x x ζ? = ∫/2trim/2 ( ) ( ' ' ) ( , ) ( ')d 'lGlI t x x x t b x x ζ? = ? ∫ . 3 VISCOUS TURBULENCE MODEL The gap flow between the ship hull and t

29、he lock wall is similar to Couette-Poiseuille shear flow, if it would be laminar. For theoretical understanding a cylindrical laminar Couette-Poiseuille flow solution is useful, which indeed can be derived analy

30、tically. Nevertheless the flow here both in the model and real scales is turbulent. Therefore a more realistic turbulence model should be applied here. In the next subsections following issues are discussed: (1) The

31、local pressure drop and its effect in momentum equation (2) Colebrook correlation for pressure drop or friction (3) Prandtl velocity profile and blockage effect of the viscous boundary layer 3.1 Local viscous frict

32、ion model based on prandtl turbulence model The fully developed turbulent flow in a pipe is well understood, where the pressure drop and the velocity profile can be evaluated by e.g. Colebrook correlation [5] and the

33、 Prandtl turbulent model [6], respectively. The pressure drop correlation is based on the local relative velocity and the local hydraulic diameter. This is especially suitable for the lock-ship interaction problem, s

34、ince the relative fluid velocity and the hydraulic diameter are different from place to place and from time to time. In particular the lock or canal wetted wall and the ship wetted surface have to be distinguished by