用一维水力学方程求取泻湖水位及潮汐汊道断面流速——以海南陵水新村港为例

本文通过一维水力学运动方程及连续性方程,得出一个反映泻湖水位变化的二阶非线性有阻尼的强迫振动方程,采用龙格-库特四步格式进行求解,并以海南陵水新村港为例,计算了泻湖水位及潮汐汊道的断面流速.研究结果表明:(1)一维水力学方程可容易地求得泻湖-潮汐汊道体系中泻湖内的水位及汊道的断面流速,计算简单快捷.(2)一维水力学方程可分析潮汐汊道体系中的一些基本现象.如潮汐汊道对潮波的"过滤器"特征;由于泻湖-潮汐汊道体系的阻尼系数较大所导致的潮波自外向泻湖传播时衰减剧烈;径流对泻湖水位及汊道流速产生有利于落潮优势的影响;风可使泻湖水位抬升或下降等.(3)无论是否考虑泻湖与潮汐汊道面积随水位的变化,一维水力学方程都具有相当大的缺陷.由于其不能反映泻湖内地形的空间变化,也不能解决漫滩与归槽等过程,在外海潮波无次生波的情况下,它本身不能产生次生潮波,因而不能正确地反映潮汐汊道体系的涨落潮历时与流速不对称,从而不能分析泥沙的净输运及潮汐汊道的稳定性问题.(4)新村港泻湖-潮汐汊道体系中潮汐汊道的断面面积大小对整个体系的稳定性及演变趋势起着控制作用.

基于Excel的水力学隐式方程求解与辅助绘图

文章通过几个实例,介绍了应用Excel求解水力学隐式方程的单变量求解法和简单迭代法。实例计算表明单变量求解法和简单迭代法具有求解过程简单,结果精度高,通用性强的特点。此外,运用实例介绍了Excel应用于水力学计算的简便辅助绘图功能。

大棚切花月季平面微灌技术的研究

土壤的供氧状况明显影响切花月季的产量和质量．在大棚土壤常规栽培条件下，为了使生长基质保持长期稳定的供氧能力，解决灌溉水的定量化和均匀化，我们在改良土壤的同时，设计了切花月季平面微灌栽培系统，并对其水力学特性、微灌喷头的有效性、根系垂直分布、微灌区内温度与湿度的动态变化等进行了研究。结果表明，微灌系统中流量与压力的水力学方程为ｑ＝２０．８６Ｈ０．６９，有效半径Ｒ＝８０ｃｍ，覆盖死角α＝１０°。与对照相比，微灌区１０～３０ｃｍ基质层内的有效根量大而分布均匀；切花月季不同群体层高内的温度相对较低、湿度较大；平均年产花量高于对照４８％，增益效果显著。

CFD-PBE simulation of a bubble column in OpenFOAM

A general CFD-PBE(computational fluid dynamics-population balance equation) solver for gas–liquid poly-dispersed flows of both low and high gas volume fractions is developed in OpenFOAM(open-source field operation and manipulation) in this work. Implementation of this solver in OpenFOAM is illustrated in detail. The PBE is solved with the cell average technique. The coupling between pressure and velocity is dealt with the transient PIMPLE algorithm, which is a merged PISO-SIMPLE(pressure implicit split operator-semi-implicit method for pressure-linked equations) algorithm. Results show generally good agreement with the published experimental data, whereas the modeling precision could be improved further with more sophisticated closure models for interfacial forces, the models for the bubble-induced turbulence and those for bubble coalescence and breakage.The results also indicate that the PBE could be solved out the PIMPLE loop to save much computation time while still preserving the time information on variables. This is important for CFD-PBE modeling of many actual gas–liquid problems, which are commonly high-turbulent flows with intrinsic transient and 3 D characteristics.

Kinetics of Forward Extraction of Boric Acid from Salt Lake Brine by2-Ethyl-1,3-hexanediol in Toluene Using Single Drop Technique

The kinetics of forward extraction of boric acid from salt lake brine by 2-ethyl-1,3-hexanediol in toluene was investigated using the single drop technique. The factors affecting the extraction rate include interfacial area between aqueous phase and organic phase, initial concentration of boric acid in aqueous phase, initial concentration of 2-ethyl-1,3-hexanediol in organic phase, and extraction temperature. The experimental results show that the extraction rate increases with the increase of the initial concentration of boric acid and2-ethyl-1,3-hexanediol, interfacial area of two phases, and temperature. With the temperature-dependence study, it is showed that the extraction is a diffusion-controlled process. The kinetic equation is presented for pH 1.0 in the aqueous phase and temperature of 318 K.

Comparative Study on the Kinetic Equations of Potassium Release from Soils

Elovicb, two-constant, parabolic diffusion, exponential, second-order, first-order and zero-order equations were used to describe the kinetic characteristics of potassium desorption from six paddy soils df Zhejiang Province in a constant electric field (44.4 V/ cm) of EUF. Results showed that the second-order and Elovich equations could describe the potassium desorption kinetics best, as evidenced by the highest correlation coefficients (r) and the lowest standard errors (SE). The first-order, two-constant and parabolic diffusion equations also described the K desorption kinetics well, as showed by the relatively high correlation coefficients and relatively low standard errors. The zero-order equation did not describe the K desorption satisfactorily with a relatively low correlation coefficient and relatively high standard error. However, the exponential equation could not be used to describe the K desorption kinetics, due to the lowest correlation coefficient and the highest standard error.

Influence of water saturation on propagation of elastic waves in transversely isotropic nearly saturated soil

Biot' s two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasitransverse wave (QSV) and the anti-plane transverse wave (SH) . Numerical results are given to illustrate theinfluence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering.

Removal of diclofenac from aqueous solution with multi-walled carbon nanotubes modified by nitric acid

Modified multi-walled carbon nanotubes(MWCNTs) were used as adsorbents for removal of diclofenac. The reaction conditions were examined. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were applied to determine appropriate equilibrium expression. The results show that the experimental data fit the Freundlich equation well. Thermodynamic parameters show that the adsorption process is spontaneous and exothermic. The kinetic study indicates that the adsorption of diclofenac can be well described with the pseudo-second-order kinetic model and the process is controlled by multiple steps.

CFD modelling of Iongwall goaf gas flow to improve gas capture and prevent goaf self-heating

CFD models have been developed to investigate the Iongwall goaf gas flow patternsunder different mining and geological control conditions.The Iongwall goaf wastreated as porous regions and gas flow was modelled as a momentum sink added to themomentum equation.Gas desorption from the caved goaf and destressed coal seamswithin the mining disturbed area was modelled as additional mass sources in the continuityequation.These CFD models were developed according to specific Iongwall layoutsand calibrated against field monitoring data.Two case studies were presented demonstratingthe application of CFD modelling of goaf gas flow characteristics for improved goafgas capture and the reduction of oxygen ingress into the goaf areas for self-heating prevention.Results from the case studies indicate that the optimum goaf drainage strategywould be a combination of shallow (near the face) and deep holes to improve the overalldrainage efficiency and gas purity.For gassy Iongwall faces retreating against the seam dip,it is recommended to conduct cross-measure roof hole drainage targeting the fracturedzones overlying the return corner,rather than high capacity surface goaf drainage deep inthe goaf.

The Third Invariant Form of Hydrodynamic Equations and Application for Definition of Water Hammer Characteristics in Pipe

There were for a long time two invariant forms of hydrodynamic equations： one was related to coordinate system of references, and the other was versus to measure units of characteristics. These both invariant forms had important roles in the development of theoretical and practical applications of hydro-aerodynamics and related industries. The third invariant form of hydrodynamic equations is one for the dimensions of spaces. For this goal, the hyper quantities （space and physics） are introduced. Then these are created we can easily cover all problems in arbitrary dimensions （3D, 2D, 1D, separate space for liquids or constituent matters）. In particularly, when they are applied to water hammer problem, which is an especially problem, we can receive immediately celerity and pressure of the event.

Global well-posedness of the MHD equations via the comparison principle

In this paper,we prove the global well-posedness of the incompressible magneto-hydrodynamics(MHD)equations near a homogeneous equilibrium in the domain R^k×T^(d-k),d≥2,k≥1 by using the comparison principle and constructing the comparison function.

Cavitation shedding dynamics around a hydrofoil simulated using a filter-based density corrected model

The unsteady turbulent cloud cavitation around a NACA66 hydrofoil was simulated using the filter-based density corrected model(FBDCM). The cloud cavitation was treated as a homogeneous liquid-vapor mixture and the effects of turbulent eddy viscosity were reduced in cavitation regions near the hydrofoil and in the wake. The numerical results(in terms of the vapor shedding structure and transient pressure pulsation due to cavitation evolution) agree well with the available experimental data, showing the validity of the FBDCM method. Furthermore, the interaction of vortex and cavitation was analyzed based on the vorticity transport equation, revealing that the cavitation evolution has a strong connection with vortex dynamics. A detailed analysis shows that the cavitation could promote the vortex production and flow unsteadiness by the dilatation and baroclinic torque terms in the vorticity transport equation.

Integrating 1D and 2D hydrodynamic,sediment transport model for dam-break flow using finite volume method

The purpose of this study is to set up a dynamically linked 1D and 2D hydrodynamic and sediment transport models for dam break flow.The 1D-2D coupling model solves the generalized shallow water equations,the non-equilibrium sediment transport and bed change equations in a coupled fashion using an explicit finite volume method.It considers interactions among transient flow,strong sediment transport and rapid bed change by including bed change and variable flow density in the flow continuity and momentum equations.An unstructured Quadtree rectangular grid with local refinement is used in the 2D model.The intercell flux is computed by the HLL approximate Riemann solver with shock captured capability for computing the dry-to-wet interface for all models.The effects of pressure and gravity are included in source term in this coupling model which can simplify the computation and eliminate numerical imbalance between source and flux terms.The developed model has been tested against experimental and real-life case of dam-break flow over fix bed and movable bed.The results are compared with analytical solution and measured data with good agreement.The simulation results demonstrate that the coupling model is capable of calculating the flow,erosion and deposition for dam break flows in complicated natural domains.

Effectiveness of Non-Markovian Methods for Quantum Discord Dynamics of Non-coupled Two-Qubit System

The dissipative dynamics of non-coupled two qubits interacting with independent reservoir is studied by solving the non-Markovian master equation. In order to examine the effectiveness of the Nakajima-Zwanzig and timeconvolutionless master equations in the description of quantum correlation dynamics, different coupled regimes are investigated. The comparison between the above two master equation methods for investigating the dynamics of quantum discord is also made. Finally, we further confirm that the two master equations should be applied in different regimes of qubits coupled to their reservoirs, respectively.

Shallow water equations for power law and Bingham fluids Dedicated to the NSFC-CNRS Chinese-French summer institute on fluid mechanics in 2010

In this note, we provide a consistant thin layer theory for power law and Bingham incompressible fluids flowing down an inclined plane under the effect of gravity. The derivation of such equations is based on formal asymptotic expansions of solutions of Cauchy momentum equations in the shallow water scaling and in the neighbourhood of steady solutions so that we can close the average equations on the fluid height h and the total discharge rate q.