WORKING PAPERS Beauty and the beast in the labor market: A ...

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• fiche de synthèse - matière potentielle : effect

WORKING PAPERS Working Paper No 2011-62 December 2011 Beauty and the beast in the labor market: A distribution regression approach Karina DOORLEY Eva SIERMINSKA

• estimates of the marginal distribution by integration of the conditional distributions over job
• counterfactual wage distributions
• people at specific wage levels
• vector of characteristics
• human capital development
• physical appearance
• hourly wage
• wages
• distribution
• people

Sujets

• Effect
• Oaxaca
• Distribution
• Physical
• People
• Specific
• Conditional

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• Publié par: jazat
• Nombre de lectures: 101
• Langue: English
• Poids de l'ouvrage: 1 Mo

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th The 11Asian International Conference on Fluid Machinery and rd The 3Fluid Power Technology Exhibition Original Paper

 Papernumber: AICFM_AT_001 November 21-23, 2011, IIT Madras, Chennai, India

The effect of motion of two floater bodies for optimization of wave energy generation system in ocean

1 11 23 Kui Ming Li, Nanjundan Parthasaraty, Young Kyu Park, Yoon Hwan Choi, Yeon Won Lee

1 Graduated School of Mechatronics Engineering, Pukyong National University, Korea San 100, Youngdang-Dong, Nam-Gu Busan, 608-739 Korea. 2 BK21, School of Mechanical Engineering, Pukyong National University, Korea San 100, Youngdang-Dong, Nam-Gu Busan, 608-739 Korea. 3 Department of Mechanical & Automotive Engineering, Pukyong National University, Korea San 100, Youngdang-Dong, Nam-Gu Busan, 608-739 Korea. [e-mail]

Abstract Wave energy is one among renewable energy, which is clean, pollution free and abundant. Nowadays, many governments around the world have been paying more and more emphasis on exploiting the wave energy. Consequently the technologies of developing power generation from wave energy have been breaking through increasingly. In order to design a optical generate system similar to the pelamis system, it is necessary to construct floating motion in different wave. This study is concentrated on the variable of wavelength. The simulation was available due to CFD. It visualizes not only wave generation in tank, but also the motion of two floater effect on the wavelength. It is compared both to displacement and rotation angle with time in different wavelengths.

Keywords:Wave Energy, CFD, 6-Degree of freedom, Floater, Wavelength

1. Introduction

Wave energy is clean and no-pollution energy. In whole world, the wave energy of 8,000- 80,000TWh/yr(or 1-10TW) is stored[1]. According to the development of renewable energy, many countries in the world give an impetus to the technology of new wave energy generation. Among many wave energy transformation systems, Fig.1 is pelamis system developed by pelamis company and in 2004 at Scotland, length 120m, diameter 3.5m and 750kw supportable prototype pelamis system is established[2]. According to a study of A. Al- Habaibeh[3], the efficient of pelamis system is higher than other system of wave energy transformation. The result of Igor Bulatov[4]'s study using EMINENT software tool, the material of wave energy will use in more big scale in case of applying the technology of pelamis.

Fig. 1Schematic diagram of Pelamis system Especially, pelamis system is a promising marine energy resource because high efficient, low equipment and maintain cost and adaptation field of this system will grow gradually. Under crisis of depletion of the resources currently, the design of the generation system using the wave energy is surely needed. Accepted for publicationPaper ID: AICFM_AT_001 Corresponding author: Kui Ming Li,Graduated School of Mechatronics Engineering, Pukyong National University,Korea 1

Figure 2Pelamis type power generation system Figure 2 shows generation theory of pelamis system. A joint region of multiple floating body fluctuate up-down or left-right and inner piston of hydraulic cylinder work a reciprocating motion keeping regular stokes. Through the work of piston, high pressure hydraulic energy is created and high pressure oil passed hydraulic motor rotate the rotor. This rotor generate the electronic energy. In order to design large-scale generation system like pelamis type in ocean, we need to study on multi floater motion, which was effected by the wave characters, also if we can optimize design the hydraulic piston travel installed in the generation system. In this study, we've realized wave generation by CFD in tank, travel and angle between two floaters in different wave. 2. Numerical Analysis  In order to realize the wave motion in free surface, we using ANSYS CFX 13. software to simulated in this study. Water and air as functioning fluid, used to multi phase model. 2.1 Continuity Equation: r # Ñ ×( r U)10  (1) ¶t Momentum Equation: ( r U) # Ñ ×( r UÄU)1 %Ñp# Ñ × t #S  (2) M ¶t r is density, U is pressure,is fluid velocity, S is source term. Shearing stress is defined by M T 2 . t 1 m (ÑU#(ÑU)% Ñ×U) 3 The homogeneous model is available in this study, which is display the volume ratio of two fluids in space. The bulk transport equations can be derived by summing the individual physic transport equations over all phases to give a single transport equation for f . ( rf )# Ñ ×( r U f %9 Ñ f )1S  (3) ¶t where: N p ∑ a a r 1 g r  (4) a 11

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N p 1 ∑ aa a U1 g r U  (5) r a 11 N p 9 1 g 9  (6) ∑ a a a 11 where g , g  is each of fluid, N  is total(Phase) number, g , r ,U,9 is each of volume ratio, density, velocity and 1 2p a aa a diffusion coefficient, separately. 2.2 Rigid Body Equation  Themotion equation for rigid body of floaters as the flows. d(P) 1F  (7) dt d( p ) 1m  (8) c dt The equations state that for a rigid body undergoing translation and rotation the rate of change of linear and angular momentu, and p and , respectively, of the rigid body is equal to the applied force and torque, m , respectively, acting on the body. c Then, the equation of motion for a translating center of mass can be expressed as the follows: m & x & F  (9) Where m  is the mass andrepresents the sum of all forces which include aerodynamic, weight of rigid body, spring and/or explicit external force. Expanding the sum of all forces, may be written as: F1F#mg%k(x%x)#F . where Aero SpringSO Ext F the aerodynamic force, isis the gravity, k the linear spring constant and is F all other external forces is Aero SpringExt acting on the body. 2.3 Boundary condition and analysis condition Figure 3 was showed that left wall is defined as the moving piston wall, which for the wave generation. top is defined as opening type. Outlet is gives the static pressure with water deep, namely, p r gh . Bottom is defined as a wall gives no-slip condition.

Figure 3Computational domain and boundary condition In order to realize wave generation like ocean we available to the piston type , which was widely used in wave maker theory. we defined the stroke length of piston in difference wave forms.[5]. Hsinh 2kh2kh S1  (10) stroke 2 cosh2kh%1 2 p where. S is the wave height,the stroke length, is k1 is wavelength, iswave number, h  iswater height. stroke Similar with equation (10) we made the equation (11), which was relation with wave properties of wave height and frequency like

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L expressed in equation (12). In linear wave theory, 0 is assumed, So, we assumed H1 in this study. 10 1L S1 ´(1%cos w t)  (11) stroke 2 10 2 p h w 1gktanh(kh)1gktanh( )  (12) L

Figure 4A rigid body has six models of motion surge(1), sway(2), heave(3), roll(4), pitch(5), and yaw(6).

 Thefloater motion is simulated by 6-degree of freedom method. In this study, we considered only heave(3) and pitch(5),which was shown in Figure 4. it was simulated by transient state, calculated total 10s in each timestep 0.1s.

3. Results and Discussions  Themain purpose in this study is the displacement and rotation angular of floaters when the regular wave comes. We choose wavelength as variable to observe the change of floater distance. Figure 5 is comparison picture of velocity vector in different wavelength after calculated 9 seconds by transient state, which was in center of XY cross-section along Z-direction.  Itcan be seen that left side is the wave generation area, so the velocity is higher than other place. And with the distance far away from left wall, the velocity is relatively lower, which was due to Ekman layer of bottom wall boundary, it is not so deep that result in the energy decreased, also energy loss during wave pass floaters.  Becauseof energy loss, wave height is lower in the small wavelength 1m, in particular near floaters. The wave height is more higher in large wavelength. The motion of both two floaters are more heavy to change.

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Figure 5Velocity vectors for different wavelength  Figure6 is the distance change between c and d with different time. The distance started from minmum distance in 1m. The distance c-d change to c'-d' wiinstalled inside hydraulic cylinder of generation system.able to design in hydraulic system inside of generation syrgest value compare with wavelength 4 and 5m. The disttimstep, it's due to phase difference, the distance increasi

Figure 6Distance change between the left floater and the right floater for various wavelength

Figure 7a left floater for base lineAngle inFigure 8a left floater for base lineAngle in  Figure7, 8 are rotation angle in left and right floater, separately. when the wave comes, both left and right floater rotate with time around the center point b and e. The rotation angle is great, when wavelength is large. The angle in left is larger than the right in same wavelength.  Likediscussed earlier in Figure 6, if we know the displacement and rotation angle, we can predict all motion information of floaters. it would be available to the optimize design in generation system of multi-floater. 4. Conclusions  The6-degree of freedom is used to analyze the 3-Dimensional CFD motions of two floaters effected by the properties of wave in this study. and got some conclusions as the follows. We made the regular wave by CFD in wave maker domain. It realizes the wave motion in fluid for rigid body. simultaneously, not only calculates the angle of rotation for both floaters, but also the distance change between two fixed points of floaters. Available to these kinds of information, which changes with time we can guide the design the optimization of generation system for wave energy.

Reference [1]Richard Bound, "Status and Research and Development Priorities, Wave and Marine Accessed Energy," UK Dept. of Trade and Industry(DTI), DTI Report # FES-R-132, AEAT Report # AEAT/ENV/1054, United Kingdom,2003. [2]Antonio F.de O.Falcao, "Wave energy utilization: A review of the technologies" Renewable and Sustainable Energy Reviews 14,pp. 899-918, 2010. [3]A.Al-Habaibeh, D. Su, J. McCague, A.Knight,“An innovative approach for energy generation from waves”, Energy Conversion and Management 51, pp. 1664-1668, 2010. [4]Igor Bulatov, Simon J Perry, Jiri J Klemes,“A new emerging energy technology- Pelamis-Demonstration of the assessment by EMINENT tool”, CHEMICAL ENGINEERING TRANSACTION, Volume 18,2009. [5]Robert G. Dean and Robert A. Dalrymple,“Water Wave mechanics, for Engineers and Scientists” [6]ANSYS 13.0 Help

Acknowledgment This research was supported by the National Research Foundation of Korea, financially backed by the Ministry of Education, Science and Technology (MEST) 2010. (No.2010-0026578)

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