| Study on the double-logarithmic profile of tidal flow velocity in the near-bed layers |
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| 作者姓名： | NI Zhihui SONG Zhiyao WU Lichun |
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| 作者单位： | NI Zhihui(Southwestern Research Institute of Water Transport Engineering, Chongqing Jiaotong University, Chongqing 400016, China; State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China);SONG Zhiyao(Key Laboratory of Virtual Geographic Environment Ministry of Education, Nanjing Normal University, Nanjing 210097, China);WU Lichun(Chongqing Education College, Chongqing 400067, China) |
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| 基金项目： | The National Natural Science Foundation of China under contract，the public welfare projects of Water Resources Ministry of China under contract，the Natural Science Foundation of the Jiangsu Higher Education institutions of China under contract |
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| 摘 要： | Tidal current velocity profile in the near-bed layers has been widely studied. The results showed that velocity profile in the near-bed layer obviously departure from the traditional logarithmic profile, due to the acceleration or deceleration. Although the logarithmic linear profile can reduce the rate of deviation from this, only it is a lower-order approximate solution. In this paper, considering the unsteady and non-linear features of tidal motion, the double logarithmic profile near-bed layers in estuarine and coastal waters is established on the assumption that the turbulent shear stress along the water depth was parabolic distribution, and on the basis of Prandtl''s mixing length theory and von Karman''s self-similar theory. Having been verified the data observed at the West Solent in the south of England, and comparison of the logarithmic linear profile, it found that the double logarithmic profile is more precious than the latter. At last, the discussed results showed that:(1) The parabolic distribution of the tidal shear stresses verified good by the field data and experimental data, can be better reflected the basic features of the tidal shear stress deviating from linear distribution that is downward when to accelerate, upward when to decelerate. (2) The traditional logarithmic velocity profile is the zero-order approximation solution of the double logarithmic profile, the logarithmic linear profile is the first order, and the logarithmic parabolic profile is the second order. (3) Ignoring the conditions of diffusion and convection in the tidal movement, the double logarithmic profile can reflect the tidal properties of acceleration or deceleration, so that the calculation of the friction velocity and roughness length are more reasonable. When the acceleration or the deceleration is about zero, the double logarithmic profile becomes the logarithmic profile.
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| 关 键 词： | 剖面 床层 对数 流速 潮汐 |
| 收稿时间： | 9/2/2008 12:00:00 AM |
| 修稿时间： | 2009/8/30 0:00:00 |
Study on the double-logarithmic profile of tidal flow velocity in the near-bed layers |
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| NI Zhihui,SONG Zhiyao,WU Lichun.Study on the double-logarithmic profile of tidal flow velocity in the near-bed layers[J].Acta Oceanologica Sinica,2009,28(6):84-92. |
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| Authors: | NI Zhihui SONG Zhiyao and WU Lichun |
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| Institution: | 1.Southwestern Research Institute of Water Transport Engineering, Chongqing Jiaotong University, Chongqing 400016, China;State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China2.Key Laboratory of Virtual Geographic Environment(Ministry of Education), Nanjing Normal University, Nanjing 210097, China3.Chongqing Education College, Chongqing 400067, China |
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| Abstract: | Tidal current velocity profile in the near-bed layers has been widely studied. The results showed that velocity profile in the near-bed layer obviously departure from the traditional logarithmic profile,due to the acceleration or deceleration. Although the logarithmic linear profile can reduce the rate of deviation from this, only it is a lower-order approximate solution. In this paper, considering the unsteady and non-linear features of tidal motion, the double logarithmic profile near-bed layers in estuarine and coastal waters is established on the assumption that the turbulent shear stress along the water depth was parabolic distribution, and on the basis of Prandtl's mixing length theory and von Karman's self-similar theory. Having been verified the data observed at the West Solent in the south of England, and comparison of the logarithmic linear profile, it found that the double logarithmic profile is more precious than the latter. At last, the discussed results showed that: (1) The parabolic distribution of the tidal shear stresses verified good by the field data and experimental data, can be better reflected the basic features of the tidal shear stress deviating from linear distribution that is downward when to accelerate, upward when to decelerate.(2) The traditional logarithmic velocity profile is the zero-order approximation solution of the double logarithmic profile, the logarithmic linear profile is the first order, and the logarithmic parabolic profile is the second order. (3) Ignoring the conditions of diffusion and convection in the tidal movement, the double logarithmic profile can reflect the tidal properties of acceleration or deceleration, so that the calculation of the friction velocity and roughness length are more reasonable. When the acceleration or the deceleration is about zero, the double logarithmic profile becomes the logarithmic profile. |
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| Keywords: | turbulence shear stress tidal current double logarithmic profile near-bed layers friction velocity roughness length |
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