• Title, Summary, Keyword: Dolphin effect

Search Result 7, Processing Time 0.038 seconds

Motion Analyses for a Very Large Floating Structure with Dolphin Mooring Systems in Irregular Waves (불규칙파 중에서 돌핀 계류된 해상공항에 대한 운동 해석)

  • 이호영;신현경;임춘규;강점문;윤명철
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
    • /
    • /
    • pp.57-62
    • /
    • 2000
  • The very large flcating structure which am be used for as airport may be as large as several kilomet wide. The first order wave forces as well as wave drift forces are very important forces on such a very large floating In the present studv, the time simulation of motion responses with dolphin-moored VLFS in waves is presented The coeffcients and wave forces involved in the equations are obtained from a three-dimensionul panel method in the frequc The horizontal drift forces and mooring forces for dolphin systems are taken into account. As for numerical example, analyses are carried out for a VLFS in irregular wave condition

  • PDF

Dynamic Analysis of Mooring Dolphin System Considering Soil Properties (지반의 강성특성을 고려한 지반-돌핀구조계의 동적해석)

  • Yi, Jin-Hak;Oh, Se-Boong;Yun, Chung-Bang;Hong, Sup;Kim, Jin-Ha
    • Journal of Ocean Engineering and Technology
    • /
    • v.12 no.3
    • /
    • pp.19-30
    • /
    • 1998
  • In this paper, the dynamic analysis of a dolphin system for mooring a floating structure such as barge mounted plant is studied. The characteristics of the soil-pile system are simplified by a set of equivalent spring elements at the mudline. To evaluate the equivalent spring constants, the finite difference method is used. Since the characteristics of the soil-pile system are nonlinear in case of soft foundation, the nonlinear dynamic analysis technique is needed. The Newmark $beta$ method incorporating the modified Newton-Raphson method(initial stiffness method) is used. A numerical analysis is performed on two mooring dolphin systems on soft foundation and rock foundation. In case of the rock foundation, the characteristics are found to be nearly linear, so the linear dynamic analysis may be sufficient to consider the foundation effect. But in case of soft foundation, the non-linearity of the foundation appears to be very signigicant, so the nonlinear dynamic analysis si needed.

  • PDF

Dynamic Response Analyses of Fixed Type Substructures for 2.5MW Class Offshore Wind Turbine

  • Song, Chang Yong;Yoo, Jaehoon
    • Journal of Advanced Research in Ocean Engineering
    • /
    • v.3 no.1
    • /
    • pp.15-24
    • /
    • 2017
  • This paper explores a series of numerical simulations of dynamic responses of multi-piles (dolphin) type substructures for 2.5MW class offshore wind turbine. Firstly computational fluid dynamics (CFD) simulation was performed to evaluate wave loads on the dolphin type substructures with the design wave condition for the west-south region of Korea. Numerical wave tank (NWT) based on CFD was adopted to generate numerically a progressive regular wave using a virtual piston type wave maker. It was found that the water-piercing area of piles of the substructure is a key parameter determining the wave load exerted in horizontal direction. In the next the dynamic structural responses of substructure members under the wave load were calculated using finite element analysis (FEA). In the FEA approach, the dynamic structural responses were able to be calculated including a deformable body effect of substructure members when wave load on each member was determined by Morison's formula. The paper numerically identifies dynamic response characteristics of dolphin type substructures for 2.5MW class offshore wind turbine.

Behaviour Analyses of Ocean Structure Due to Ship Collision (선박의 충돌로 인한 해양구조물의 거동 해석)

  • 이호영
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
    • /
    • /
    • pp.103-107
    • /
    • 2001
  • When ship claps against the ocean structure sited at shallow water, the time simulation of motion responses of dolphin-moored ocean structure is presented. The equatien of motion based on Cummin's theory of impulse responses are employed, and solved in time domain by using the Newmark $\beta$ method. The added mass and damping coefficients involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The impact forces due to ship collision are modeled as two method, and those are elastic and non-elastic collisions. The mooring forces for dolphin systems of scean structure are considered as linear spring system.

  • PDF

Analyses on the Behaviour of Ocean Structure Due to Ship Collision (선박의 충돌로 인한 해양구조물의 거동 해석)

  • 이호영;박종환;곽영기
    • Journal of Ocean Engineering and Technology
    • /
    • v.15 no.4
    • /
    • pp.115-119
    • /
    • 2001
  • The simulation of motion responses of a dolphin-moored ocean structure in shallow water when it cllides with a ship, has been carried out. The equation of motion in the time domain according to Cummin's theory is employed, and solved by making use of the Newmark-${\beta}$ method. The added mass and damping coefficients involved in the equations are abtained from a three-dimensional panel method in the frequency domain. The impact forces due to ship collision are calculated using both the elastic and non-elastic modelings. The mooring forces for dolphin systems of ocean structure are regarded as linear spring forces.

  • PDF

Thrust Performance Improvement of a Linear Induction Motor

  • Lee, Hyung-Woo;Park, Chan-Bae;Lee, Byung-Song
    • Journal of Electrical Engineering and Technology
    • /
    • v.6 no.1
    • /
    • pp.81-85
    • /
    • 2011
  • The end effect of a linear induction motor (LIM) has been known for several decades, especially in high speed operation. The exit part of the primary is not dealt as extensively as the entry part because of its minor effect. However, the exit part is one of the keys to weaken the dolphin effect, which occurs in high speed operation. In this paper, the concept of the virtual primary core is introduced, and chamfering of the primary outlet teeth is proposed to minimize the longitudinal end effect at the exit zone. For this, LIM for the high-speed train is designed and analyzed by using finite element method. Results confirm that chamfering can improve thrust performance effectively.

Trial manufacture of dual frequency acoustic pinger to minimize cetacean bycatch (고래류 혼획을 최소화하기 위한 다주파 음향 경고시스템의 시험 제작)

  • Lee, Yoo-Won;Shin, Hyeong-Il;Kim, Seok-Jae;Seo, Du-Ok;Lee, Dae-Jae;Kim, Zang-Geun;Hwang, Doo-Jin
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.41 no.3
    • /
    • pp.207-212
    • /
    • 2005
  • Dual frequency acoustic pinger(AP) was manufactured to reduce study effect by long-term use of developed single frequency AP to prevent cetacean bycatch. Directivity characteristic of transducer was the omnidirectional pattern which showed less than ${\pm}3dB$ the change range of sensitivity on the beam pattern of right and left. Source power level(SPL) was 1384311pa with epoxy window before casing however after casing 1170B11Pa at sea. Dual frequency Af was tested to identify the avoidance behavior of bottlenose dolphin by its working. However the efficiency of dual frequency AP about the study effect was verified experiment repeatedly using single and dual frequency AP.