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RISS 인기검색어
- 검색키워드
- 저자 : Wei-Haur Lam (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Analysis of the 3D Zone of Flow Establishment from a Ship's Propeller
Wei-Haur Lam,Gerard Hamill,Desmond Robinson,Srinivasan Raghunathan,Yongchen Song 대한토목학회 2012 KSCE Journal of Civil Engineering Vol.16 No.4
In the present study an experimental investigation of the time-averaged velocity and turbulence intensity distributions from a ship’s propeller, in “bollard pull” condition (zero speed of advance), is reported. Previous studies have focused mainly on the velocity profile of not a rotating ship propeller but a plain jet. The velocity profile of a propeller is investigated experimentally in this study. The velocity measurements were performed in laboratory by using a Laser Doppler Anemometry (LDA). The measurements demonstrated two-peaked ridges velocity profile with a low velocity core at the centre within the near wake. The two-peaked ridges combined to be one-peaked ridge at 3.68 diameters downstream indicating the end of the zone of flow establishment. The study provides useful information from a rotating ship’s propeller rather than a simplified plain jet to researchers investigating flow velocity generated from a propeller and probably resulting local scouring.
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Predictions of Wake and Central Mixing Region of Double Horizontal Axis Tidal Turbine
Stephen Oppong,Wei-Haur Lam,Jianhua Guo,Leng Mui Tan,Zhi Chao Ong,Wah Yen Tey,Yun Fook Lee,Zaini Ujang,Ming Dai,Desmond Robinson,Gerard Hamill 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.7
Predicting the velocity distribution of double horizontal axis tidal turbines (DHATTs) is significant for the effective development of tidal streams. This current research gives an account on double turbine wake theory and flow structure of DHATT connected to single support by using the joint axial momentum theory and computational fluid dynamics (CFD) method. Characteristics of single turbine wake were previously studied with two theoretical equations predicting the initial upstream velocity closer to the turbine, and it’s lateral distributions along the downstream of the turbine. This current works agreed with the previous wake equations, which was used for predicting the velocity region along the downstream of the turbines. Flow field separating the two turbines is complicated in nature due to the indirect disturbance of turbines and no report was found on this central region. The Central region in the downstream flow is initially suppressed due to the blockage effects with a high velocity close to the free stream. Lateral expansion of two turbine wakes penetrated the central region with velocity reduction and followed by the flow recovery further downstream. This work provides more understandings of the wake and its central mixing region for double turbines with a proposed theoretical model.
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Jinxin Jiang,Wei-Haur Lam,Yonggang Cui,Tianming Zhang,Chong Sun,Jianhua Guo,Yanbo Ma,Shuguang Wang,Gerard Hamill 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3
The current research proposed the theoretical model for ship twin-propeller jet based on the axial momentum theory and Gaussian normal distribution. The twin-propeller jet model is compared to the more matured single propeller jet model with good agreement. Computational Fluid Dynamics (CFD) method is used to acquire the velocity distribution within the twin-propeller jet for understanding of flow characteristics and validation purposes. Efflux velocity is the maximum velocity within the entire jet with strong influences by the geometrical profiles of the blades. Twin-propeller jet model showed four-peaked profile at the initial plane downstream to the propeller compared to the two-peaked profile from a single-propeller. The four-peaked profile merges to be twopeaked velocity profile and then one-peaked profile due to the fluid mixing. Entrainment occurs between the ambient still water outside and the rotating flow within jet due to the high velocity gradient. The research proposes a twin-propeller jet theory with a serial of equations enabling the predictions of velocity magnitude within the jet.
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