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Mechanism of local scour around submarine pipelines based on numerical simulation of turbulence model

Acta Oceanologica Sinica 2006年第2期25卷 142-152页

作者： L Lin1*, LI Yucheng1,3, CHEN Bing21. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China2. School of Civil and Hydraulic Engineering, Dalian University of Technology, Dalian 116024, China3. R&D center of civil Engineering Technology, Dalian University, Dalian 116622, ChinaReceived 20 July 2005 accepted 14 December 2005 State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China randd Center of Civil Engineering Technology Dalian University Dalian 116622 China School of Civil and Hydraulic Engineering Dalian University of Technology Dalian 116024 China

The mechanism of local scour around submarine pipelines is studied numerically based on a renormalized group (RNG) turbulence model. To validate the numerical model, the equilibrium profiles of local scour for two cases are simulated and compared with the experimental data. It shows that the RNG turbulence model can give an appropriate prediction for the configuration of equilibrium scour hole, and it is applicable to this situation. The local scour mechanism around submarine pipelines including the flow structure, shear stress distribution and pressure field is then analyzed and compared with experiments. For further comparison and validation, especially for the flow structure, a numerical calculation employing the large eddy simulation (LES) is also conducted. The numerical results of RNG demonstrate that the critical factor governing the equilibrium profile is the seabed shear stress distribution in the case of bed load sediment transport, and the two-equation RNG turbulence model coupled with the law of wall is capable of giving a satisfying estimation for the bed shear stress. Moreover, the piping phenomena due to the great difference of pressure between the upstream and downstream parts of pipelines and the vortex structure around submarine pipelines are also simulated successfully, which are believed to be the important factor that lead to the onset of local scour.

关键词： submarine pipeline mechanism of local scour renormalized group turbulence model large eddy simulation piping

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Factors Influencing the Morphological Characteristics of Village Chickens’ Genetic Resources in the Abu-Dhabi Emirate, UAE

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Open Journal of Animal Sciences 2018年第1期8卷 87-103页

作者： Mohammad J. Tabbaa Hussein H. Hassanin randd Abu-Dhabi Food Control Authority Abu-Dhabi UAE Department of Animal Production School of Agriculture The University of Jordan Amman Jordan Animal Production Abu-Dhabi Food Control Authority Abu-Dhabi UAE

The study was accomplished to identify the characteristics of village chickens’ (VCs) genetic resources in the Abu-Dhabi Emirate of United Arab Emirate (UAE) and to study factors affecting these characteristics. Each bird was individually observed, identified, measured and characterized of thirteen VCs pure breeds and crossbreds. The overall VCs had normal feather morphology (95.1%) and distribution (77%). Except for Fayomi chickens which were 100% mottled, no specific plumage pattern was found. Almost 52% of the VCs had white skins. Six different colors were reported for the shanks and maximized for white shanks (34.3%). Large breasts (46%) were more available. The predominant plumage color was mixed colors (37.5%). Face size tended to be small (42.8%) to medium (40.4%). More brown (48.9%) then orange (27.3%) eyes were found. Dark (49.7%) beaks were more available than white (28.6%) or yellow (21.7%) beaks. The distribution of wattle colors was similar to that of ear-lob colors with some variation. Small wattles (41.9%) were most available. Single comb (82.4%) is the most available;11 other types and one with no comb were represented with low frequencies. In the whole sample, red and white combs (56.7%) were the most available;however, plain red (23.8%) and red and black (15.5%) were represented. Results of factors influence showed that body weight was high significantly (P < 0.01) influenced by the interaction between both breed and region and breed and sex. Significant (P < 0.01) influence of interaction was observed between breed and location on body length, wing span and shank length. The interaction between breed and sex only significantly (P < 0.01) influenced shank length. Though, all main effects of breed, sex and region significantly (P < 0.01) influenced continuous measures. Most morphological characteristics were significantly (P < 0.01) different among breeds. This study reported the morphological characteristics of the different VCs breeds kept in Abu-

关键词： Body Weight Breeds Morphological Characteristics UAE Village Chickens

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