The wave plus current flow over vortex ripples at an arbitrary angle     

Ken Haste Andersen  Carla Faraci   《Coastal Engineering》2003,47(4):431

This work concerns the wave plus current flow over a sand bed covered by vortex ripples, with the current and the waves coming from different angles. Experiments were performed in a basin, where current and waves were perpendicular, in order to determine the conditions (current strength) leading to a regular ripple pattern formation. Numerical simulations were conducted changing the direction between the waves and the current from 0° to 90° and the ratio between the current strength and the wave orbital velocity from 0.2 to 1.5. Close to the bed, the current aligns parallel to the ripple crests, leading to a veering current profile with the vertical coordinate. The current-related friction coefficient was calculated. It was found that it decreases as the angle approaches 90°, while it increases for decreasing values of the current with a trend that can be described by a power law.  相似文献   

Dynamics analysis for flux of carbon dioxide across seasurface   总被引：1，自引：0，他引：1  

Zhang Huai  Sun Fu 《海洋学报(英文版)》1996,15(4):447-455

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Dynamics of the turbidity maximum in King Sound, tropical Western Australia   总被引：1，自引：0，他引：1  

E. Wolanski  S. Spagnol 《Estuarine, Coastal and Shelf Science》2003,56(5-6):877-890

King Sound is a 100-km-long embayment located in tropical northwestern Australia with a spring tidal range of 11 m. This is the second largest tide in the world after the Bay of Fundy in Canada. Intertidal areas cover about 800 km². The upper reaches of the sound are turbid with fine suspended sediment concentration reaching 3 kg m⁻³. Field studies of the dynamics of water and fine sediment were carried out in the dry seasons of 1997 and 1998. The tide was a propagating wave, shoaling and dissipating by friction as it entered the sound. This mode of propagation generated an asymmetric tidal current with a stronger current at flood than at ebb. An evaporation-driven salinity maximum zone was found in the upper reaches of the sound, and this was also where the turbidity maximum occurred. Tidal pumping by the tidal asymmetry and, possibly, the biological filter formed by muddy marine snow, trapped the fine sediment in the upper regions of King Sound. Wind-driven waves contributed significantly to entrainment of bottom fine sediment, possibly through wave pumping of the sediment and not wave-induced orbital velocities. Field data suggest that erosion of bottom fine sediment was proportional to the sixth power of the tidal current and the third power of the wave height.  相似文献   

Time domain BEM analysis of dynamic response of a cylinder embedded in soil with frictional slip at the interface     

Yang-De Feng  Yue-Sheng Wang  Zi-Mao Zhang 《Soil Dynamics and Earthquake Engineering》2003,23(4):303-311

A 2D time domain boundary element method (BEM) is developed to study the dynamic response of a cylinder embedded in soil. The interface is assumed in contact with Coulomb friction. For the incident wave strong enough, local slip may occur along the interface. We suppose a pressure enough high is applied on the interface so that separation is impossible. The present problem is indeed a nonlinear boundary value problem since the mixed boundary conditions involve unknown intervals (slip and stick regions). In order to determine the unknown intervals, an iterative technique is developed. As an example, we consider the scattering of a circular cylinder embedded in an infinite solid. Numerical results for the near field solutions are presented. The nonlinear nature of the system is discussed.  相似文献   

Yield surfaces and flow rules for deformation of granular materials with a volume constraint     

C.M. Sands  H.W. Chandler 《Computers and Geotechnics》2010

This paper presents a procedure for developing yield functions with consistent flow rules for granular materials from a family of two parameter dissipation functions in combination with appropriate kinematic constraints. Through a mathematical procedure described in the paper, a general formulation is developed that can, by adjusting the values of the two parameters, reproduce a wide range of yield surfaces, including the Drucker–Prager, Matsuoka–Nakai, and Lade–Duncan. Specifically, an analytical expression for the yield function is obtained in terms of a parameter that is a selected solution to a high order polynomial. The roots of this polynomial can always be found using the eigenvalues of the companion matrix and instructions on how to select the appropriate root are given in the paper. Two ways of incorporating anisotropy into the procedure are explored and the role within it of the recent history of deformation is examined.  相似文献   

Tides and mixing in the northwestern East China Sea,Part II: Near-bottom turbulence   总被引：1，自引：0，他引：1  

Iossif Lozovatsky  Zhiyu Liu  Hao Wei  H.J.S. Fernando 《Continental Shelf Research》2008

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Nonlinear regression model for peak-failure strength of rockfill materials in general stress space     

《地学前缘(英文版)》2018,9(6):1699-1709

A nonlinear regression model for peak-failure strength prediction of rockfill materials is proposed. It is based on the relationship between the peak-failure stress ratio and the normalized confining pressure as well as the relationship between the normalized peak-failure stress ratio and the exponent function of the intermediate principal stress ratio. This model can well predict the variations of the peak-failure stress ratio with the initial confining pressure and the intermediate principal stress ratio for different rockfill materials under different general stress paths. Comparisons of the measured and predicted results show that the peak-failure strength under the constant-p' and constant-b path is larger than that under the constant-σ'_3 and constant-b path. The predictive capacity of the proposed model for the peakfailure stress ratio is better than that for the peak-failure friction angle.  相似文献   

The effect of spatially varying earthquake ground motions on the stochastic response of bridges isolated with friction pendulum systems   总被引：1，自引：0，他引：1  

Sevket Ates  Alemdar Bayraktar  A. Aydin Dumanoglu 《Soil Dynamics and Earthquake Engineering》2006,26(1):31-44

In this paper, a comprehensive investigation of the effect of spatially varying earthquake ground motions on the stochastic response of bridges isolated with friction pendulum systems is performed. The spatially varying earthquake ground motions are considered with incoherence, wave-passage and site-response effects. The importance of the site-response effect, which arises from the difference in the local soil conditions at different support points of the isolated bridge, is investigated particularly. Mean of maximum and variance response values obtained from the spatially varying earthquake ground motions are compared with those of the specialised cases of the ground motion model. It is shown that site-response component of the spatially varying earthquake ground motion model has important effects on the stochastic response of the isolated bridges. Therefore, to be more realistic in calculating the isolated bridge responses, the spatially varying earthquake ground motions should be incorporated in the analysis.  相似文献   

摩擦摆支座在单层球面网壳结构中的隔震分析   总被引：1，自引：1，他引：1  

薛素铎  赵伟  李雄彦 《世界地震工程》2007,23(2):41-45

将摩擦摆支座（FPS）应用于单层球面网壳结构的隔震，给出了隔震网壳结构的运动方程。通过对比分析不同强度地震动输入条件下的结构动力响应特征，考察了FPS支座应用于网壳结构隔震的有效性和适用性。研究结果表明，在不同强度的地震动作用下，隔震结构的节点加速度峰值和杆件轴力峰值都得到了有效控制，且地震动强度越大，控制效果越好。  相似文献   

Power-law index for velocity profiles in open channel flows     

Nian-Sheng Cheng 《Advances in water resources》2007

Turbulence theory has demonstrated that the log law is one of the established theoretical results for describing velocity profiles, which is in principle applicable for the near-bed overlap region, being less than about 20% of the flow depth. In comparison, the power law that is often presented in an empirical fashion could apply to larger fraction of the flow domain. However, limited information is available for evaluating the power-law exponent or index. This paper attempts to show that the power law can be derived as a first-order approximation to the log law, and its power-law index is computed as a function of the Reynolds number as well as the relative roughness height. The result obtained also coincides with the fact that the one-sixth power included in the Manning equation is of prevalent acceptance, while higher indexes would be required for flows over very rough boundaries.  相似文献