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RISS 인기검색어
- 검색키워드
- 저자 : Lee Kee Quen (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Vortex-induced vibration characteristics of a low-mass-ratio flexible cylinder
Lee Kee Quen,Aminudin Abu,Naomi Kato,Pauziah Muhamad,Kang Hooi Siang,Lim Meng Hee,Mohd Asamudin A Rahman 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.5
A laboratory experiment is conducted is to investigate the behaviour of a low-mass-ratio and high aspect ratio flexible cylinder under vortex-induced vibration (VIV). A flexible cylinder with aspect ratio of 100 and mass ratio of 1.17 is towed horizontally to generate uniform flow profile. The range of Reynolds number is from 1380 to 13800. Vibration amplitude, in-line and cross-flow frequency response, amplitude trajectory, mean tension variation and hydrodynamic force coefficients are analyzed based on the measurement from strain gauges, load cell and CCD camera. Experimental results indicate that broad-banded lock-in region is found for the cylinder with a small Strouhal number. The frequency switches in the present study indicates the change of the VIV phenomenon. The hydrodynamic force responses provide more understanding on the VIV of a low mass ratio cylinder.
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Sloshing suppression by floating baffle
Kang, Hooi-Siang,Md Arif, Ummul Ghafir,Kim, Kyung-Sung,Kim, Moo-Hyun,Liu, Yu-Jie,Lee, Kee-Quen,Wu, Yun-Ta Techno-Press 2019 Ocean systems engineering Vol.9 No.4
Sloshing is a phenomenon which may lead to dynamic stability and damages on the local structure of the tank. Hence, several anti-sloshing devices are introduced in order to reduce the impact pressure and free surface elevation of liquid. A fixed baffle is the most prevailing anti-sloshing mechanism compared to the other methods. However, the additional of the baffle as the internal structure of the LNG tank can lead to frequent damages in long-term usage as this structure absorbs the sloshing loads and thus increases the maintenance cost and downtime. In this paper, a novel type of floating baffle is proposed to suppress the sloshing effect in LNG tank without the need for reconstructing the tank. The sloshing phenomenon in a membrane type LNG tank model was excited under sway motion with 30% and 50% filling condition in the model test. A regular motion by a linear actuator was applied to the tank model at different amplitudes and constant period at 1.1 seconds. Three pressure sensors were installed on the tank wall to measure the impact pressure, and a high-speed camera was utilized to record the sloshing motion. The floater baffle was modeled on the basis of uniform-discretization of domain and tested based on parametric variations. Data of pressure sensors were collected for cases without- and with-floating baffle. The results indicated successful reduction of surface run-up and impulsive pressure by using a floating baffle. The findings are expected to bring significant impacts towards safer sea transportation of LNG.
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Kang, Hooi-Siang,Kim, Moo-Hyun,Bhat Aramanadka, Shankar S.,Kang, Heon-Yong,Lee, Kee-Quen Techno-Press 2017 Ocean systems engineering Vol.7 No.3
Excessive dynamic-tension variations on the top-tensioned risers (TTRs) deteriorate the structural integrity and cause potential safety hazards. This phenomenon has become more remarkable in the development of deep-water fields with harsher environmental loads. The conventional prediction method of tension variations in hydro-pneumatic tensioner (HPT) has the disadvantage to underestimate the magnitude of cyclic loads. The actual excessive dynamic tension variations are larger when considering the viscous frictional fluid effects. In this paper, a suppression method of tension variations in HPT is modeled by incorporating the magneto-rheological (MR) damper and linear-force actuator. The mathematical models of the combined HPT and MR damper are developed and a force-control scheme is introduced to compensate the excessive tension variations on the riser tensioner ring. Numerical simulations and analyses are conducted to evaluate the suppression of tension variations in HPT under both regular- and irregular-wave conditions for a drilling riser of a tensioned-leg platform (TLP). The results show that significant reduction of tension variations can be achieved by introducing the proposed system. This research has provided a theoretical foundation for the HPT tension control and related structural protection.
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