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151.
152.
This numerical investigation was carried out to advance mechanistic understanding of sediment transport under sheet flow conditions. An Euler–Euler coupled two-phase flow model was developed to simulate fluid–sediment oscillatory sheet flow. Since the concentration of sediment particles is high in such flows, the kinematics of the fluid and sediment phases are strongly coupled. This model includes interaction forces, intergranular stresses and turbulent stress closure. Each phase was modeled via the Reynolds-Averaged Navier–Stokes equations, with interphase momentum conservation accounting for the interaction between the phases. The generation and transformation of turbulence was modeled using the two-equation k–ε turbulence model. Concentration and sediment flux profiles were compared with experimental data for sheet flow conditions considering both symmetric and asymmetric oscillatory flows. Sediment and fluid velocity variations, concentration profiles, sediment flux and turbulence parameters of wave-generated sheet flow were studied numerically with a focus on sediment transport characteristics. In all applications, the model predictions compared well with the experimental data. Unlike previous investigations in which the flow is driven by a horizontal pressure gradient, the present model solves the Navier–Stokes equations under propagating waves. The model’s ability to predict sediment transport under oscillatory sheet flow conditions underscores its potential for understanding the evolution of beach morphology. 相似文献
153.
A two-dimensional semi-analytical heat transfer solution is developed and a parameter sensitivity analysis performed to determine the relative importance of rock material properties (density, thermal conductivity and heat capacity) and hydrogeological properties (hydraulic gradient, fracture aperture, fracture spacing) on the ability to heat fractured rock using thermal conductive heating (TCH). The solution is developed using a Green’s function approach in which an integral equation is constructed for the temperature in the fracture. Subsurface temperature distributions are far more sensitive to hydrogeological properties than material properties. The bulk ground water influx (q) can provide a good estimate of the extent of influx cooling when influx is low to moderate, allowing the prediction of temperatures during heating without specific knowledge of the aperture and spacing of fractures. Target temperatures may not be reached or may be significantly delayed when the groundwater influx is large. 相似文献
154.
在分析辽宁能源状况和水资源量与分布状况及生态环境现状的基础上,揭示了经济发展与生态环境方面存在的矛盾,针对辽宁的能源利用率低、水环境安全受到威胁、区域环境污染集中等问题,结合辽宁实际情况,对此进行了探讨并提出了对策与建议。 相似文献
155.
A. N. V. Satyanarayana U. C. Mohanty N. V. Sam Swati Basu V. N. Lykossov 《Journal of Earth System Science》2000,109(2):293-303
An attempt has been made to study the marine boundary layer characteristics over Bay of Bengal using BOBMEX (Bay of Bengal
and Monsoon Experiment) pilot experiment data sets, which was conducted between 23rd October and 12th November 1998 on board
ORV Sagar Kanya. A one-dimensional multilevel atmospheric boundary layer with TKE-ε closure scheme is employed to study the
marine boundary layer characteristics. In this study two synoptic situations are chosen: one represents an active convection
case and the other a suppressed convection. In the present article the marine boundary layer characteristics such as temporal
evolution of turbulent kinetic energy, height of the boundary layer and the airsea exchange processes such as sensible and
latent heat fluxes, drag coefficient for momentum are simulated during both active and suppressed convection. Marine boundary
layer height is estimated from the vertical profiles of potential temperature using the stability criterion. The model simulations
are compared with the available observations. 相似文献
156.
E.
afak 《Soil Dynamics and Earthquake Engineering》2000,20(1-4)
Seismic safety of structures depends on the structure's ability to absorb the seismic energy that is transmitted from ground to structure. One parameter that can be used to characterize seismic energy is the energy flux. Energy flux is defined as the amount of energy transmitted per unit time through a cross-section of a medium, and is equal to kinetic energy multiplied by the propagation velocity of seismic waves. The peak or the integral of energy flux can be used to characterize ground motions. By definition, energy flux automatically accounts for site amplification. Energy flux in a structure can be studied by formulating the problem as a wave propagation problem. For buildings founded on layered soil media and subjected to vertically incident plane shear waves, energy flux equations are derived by modeling the building as an extension of the layered soil medium, and considering each story as another layer. The propagation of energy flux in the layers is described in terms of the upgoing and downgoing energy flux in each layer, and the energy reflection and transmission coefficients at each interface. The formulation results in a pair of simple finite-difference equations for each layer, which can be solved recursively starting from the bedrock. The upgoing and downgoing energy flux in the layers allows calculation of the energy demand and energy dissipation in each layer. The methodology is applicable to linear, as well as nonlinear structures. 相似文献
157.
利川判断地震序列能蕈释放衰减是否异常的Ec—k量板,汁算了云南及附近地区39次巾强地震序列的能量衰减系数k值。结果显示:①当判别指标k〉1时,地震序列能量衰减处于正常状态;当k≤1时,判断地震序列能量衰减出现异常,其后发生更大地震或强余震的町能什较大。②对云南地区中强地震序列的榆验表明,有74%的地震序列符合上述判别指标。③用相同的地震进行了地震序列频度衰减系数^值的计算,发现符合h值判别指标的地震序列占统计际本的锄%。④对日常地震跟踪临视中遇到的二次典型地震序列详细分析,发现用k值力。法无论对中小地震序列还是巨震序列,预测效果均较好。 相似文献
158.
159.
160.
Feasible numerical method for a structural analysis of a pipeline configuration during the installation process is presented. The method considers the whole pipeline, which is partially suspended and partially laid-on a seabed, as a single continuous segment, and is valid for a complete range of laying angles between 0°–90°, i.e., valid for both S-lay and J-lay configurations. The method accounts for a pipeline–seabed interaction and the pipeline is modeled by means of nonlinear large deformation beam theory. The numerical solution is carried out in an incremental-iterative manner by following the actual pipeline installation process, and thus allowing efficient treatment of pipeline-seabed interaction circumventing the further complexities with contact detection. At each increment, the length of the pipeline is increased and new sequential equilibrium configuration is assessed by direct minimization of a total potential energy approximated as a Riemann sum, which yields algebraic system of nonlinear finite difference equations that is further solved by iterations with Newton-Raphson technique. The simplicity, flexibility and robustness of the proposed method allow to enhance the efficiency of engineering calculations and design. Accounting for a bending stiffness in a suspended part allows analyzing variations in laying angle and lay tension independently. The method convergence is validated and compared with Abaqus. The results are in an excellent agreement. Moreover, the comparison with Abaqus shows that for the selected parameters the assumption that the pipeline is inextensible and unshearable is very reasonable. Representative parametric study is conducted to demonstrate the feasibility of the method. Parametric study considers the effects of laying angle (0°–90°), lay tension, laying water depth (up to 3000 m) and seabed stiffness. 相似文献