水力瞬变特征线法和隐式差分法的对比分析

液体在长输管道内不稳定流动问题可以采用各种数直解法并借助计算机来进行处理,如特征线法、隐式差分法等。特征线法是广泛使用的数值方法.隐式差分法在液体长输管道不稳定流动问题分析中应用则比较少。分析了长输管道水力瞬变特征线法和隐式有限差分法的优缺点,并结合算例分析,指出隐式差分法适合于长输管道水力瞬变分析,计算误差较小。

确定输油管道进出站压力的水力坡降线平移方法

对于具有多泵(减压)站的输油管道,在给定输送油品状况和热力状况的条件下,各管段的水力坡降线随之确定,管道的动力费用仅与各站的增压或减压值有关。为确定全线各站的进、出站压力,建立以动力费用作为目标函数,以管道的承压能力和允许最小压力作为约束条件的优化模型。而后将其转化为各站相对独立的以进站压力作为目标函数的优化模型,并提出了求解该模型的水力坡降线平移方法。该方法计算简便,易于编程,特别适合于成品油管道,并已应用于兰成渝成品油管道的运行调度系统。

基于水力计算和SWMM模型的排水设计应用

文中梳理了城镇排水防涝和流域防洪标准的衔接与联系,对城市内涝的成因进行分析,一是城镇排水设施无法应对短历时强降雨情况,二是因受纳水体水位顶托影响,雨水无法及时排放。文中以滁州市九梓大道为例,通过水力计算和SWMM模型对水位线进行了研究,结果表明,道路最不利点未发生节点积水,不会造成城市内涝。文中结论可为后期研究河道水位对城市内涝的影响提供借鉴。

热水地面辐射采暖常用加热管材水力计算

介绍了热水地面辐射采暖常用管材的水力计算方法,得出了6种常用管材的水力计算表并绘制了水力线算图。对塑料管材和金属Cu管材进行水力比较,结果表明相同条件下Cu管材水力较优;在塑料类管材中,PE-X管材水力较优。

Design and Application of Automatic Test System of Soil Water Characteristic Curve

[Objective] In order to better meet the requirement of crops on a more and more accurate water content under various planting environment of modern agri-culture, an automatic test system of soil water characteristic curve was designed by combining the conceptions of soil moisture content and soil water potential. [Method] Electronic soil moisture tension meter was used to determine the real-time tension value of soil moisture in the tested container, and the electronic Weigh sensor was used to determine soil Weigh. Minusing method was used to calculate soil moisture content, based on which the soil water characteristic curve was plotted. [Result] Through the filed survey of 2 different kinds of soil in Jiangsu Province, the results were as fol ows： soil of different composition showed different trend in soil water characteristic curve that the soil water characteristic relation of the sandy soil in the old course of the Yel ow River in Xuzhou was Y=-0.000 2X3＋0.027 7X2-1.644 5X＋38.161, R2=0.991 9; while the soil water characteristic relation of the saline-alkali soil in Jinhai Farm of Dafeng was Y=-0.00 2X2-0.426X＋39.905, R2=0.991 3. [Con-clusion] The automatic test system of soil water characteristic curve soil water char-acteristics curve could reflect soil moisture content and soil water potential, as wel as reflect the effectiveness of soil water to plant growth, providing basis for the sci-entific irrigation.

瓮福中低品味磷精矿浆管道输送系统工艺设计

瓮福集团针对磷矿石品位较低,大量资源不能利用的现状,为提高资源利用率,投资7亿元进行了中低品位磷矿石的扩建工程,其中新建磷精矿管道输送系统,将磷精矿浆从新龙坝选矿厂输送至马场坪工业场地,输送距离46.9km。文章主要介绍了磷精矿浆管道系统的输送工艺设计,设计时考虑到实际生产中不可避免的产量波动,设计背压可调的消能站实现流量多级调节。通过调节泵速和消能站中消能孔板组合的运行模式,矿浆可控制在最低能耗下输送,生产灵活性较高,吨矿运输成本大幅降低,由原来的0.2元/吨·公里降低到0.1元/吨·公里,经济效益显著。新管道系统于2013年5月成功投产使用,技术装备和经济指标达到世界先进水平。

Aniracetam attenuates H_2O_2-induced deficiency of neuron viability, mi-tochondria potential and hippocampal long-term potentiation of mice in vitro

Objective It is known that free radicals are involved in neurodegeneration and cognitive dysfunction, as seen in Alzheimer＇s disease （AD） and aging. The present study examines the protective effects of aniracetam against H2O2- induced toxicity to neuron viability, mitochondria potential and hippocampal long-term potentiation （LTP）. Methods Tetrazolium salt 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide （MTT） was used to detect neuronal viability. MitoTracker Red （CMX Ros）, a fluorescent stain for mitochondria, was used to measure mitochondria potential. Electrophysiological technique was carried out to record hippocampual LTE Results H2O2 exposure impaired the viability of neurons, reduced mitochondria potential, and decreased LTP in the CA region of hippocampus. These deficient effects were significantly rescued by pre-treatment with aniracetam （10 ～100μmol/L）. Conclusion These results indicate that aniracetam has a strong neuroprotective effect against H2O2-induced toxicity, which could partly explain the mechanism of its clinical application in neurodegenerative diseases.

Numerical Analysis of the High Skew Propeller of an Underwater Vehicle

A numerical analysis based on the boundary element method （BEM） was presented for the hydrodynamic performance of a high skew propeller （HSP） which is employed by an underwater vehicle （UV）. Since UVs operate at two different working conditions （surface and submerged conditions）, the design of such a propeller is a cumbersome task. This is primarily due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different. Therefbre, some factors are necessary for the design of the optimum propeller to utilize the power at the mentioned conditions. The design objectives of the optimum propeller are to obtain the highest possible thrust, minimum torque, and efficiency. In the current study, a 5-bladed HSP was chosen for running the UV. This propeller operated at the stern of the UV hull where the inflow velocity to the propeller was non-uniform. Some parameters of the propeller were predicted based on the UV geometrical hull and operating conditions. The computed results include the pressure distribution and the hydrodynamic characteristics of the HSP in open water conditions, and comparison of these results with those of the experimental data indicates good agreement. The propeller efficiency for both submerged and surface conditions was found to be 67% and 64%, respectively, which compared to conventional propellers is a significantly higher efficiency.

长距离重力有压流输水管系统连通管布置研究

为更合理、科学地布置连通管,使得双管并联长距离重力有压流管路系统更经济、安全,建立了一个理想的双管并联长距离重力有压流输水管路模型。该模型管道采用相同的材质、相同的管径,忽略连通管长度以及连通管桥接带来的水力损失,并假设输水系统的局部损失系数均匀分布。然后根据水力学原理,建立了基本的能量方程和连续方程来对该模型进行求解。再结合实际工程的具体设计要求,得到一个关于相邻连通管间距的数学表达式,进而提出了一种双管并联长距离重力有压流输水管路系统连通管布置的设计方法。最后定量分析了相邻连通管间距的影响因素及其对压力水力坡降线、输水流量的影响。结果表明:相邻的两根连通管之间的距离仅与上下游水位、管线中心点高程、输水管线建筑物、连通管的位置以及最低水量的要求有关,与管材、管径、管内平均流速、输水流量、水力损失系数无关;相邻的两根连通管间距越大,故障段前后的并联管和故障段单管的水力坡降线就越缓;连通管桥接后的输水流量与检修段的水力损失在整个输水系统总损失的占比有关。研究结果对双管并联长距离重力有压流输水管路系统连通管布置具有一定的指导意义。

Nonlinear control for a class of hydraulic servo system

The dynamics of hydraulic systems are highly nonlinear and the system may be subjected to non-smooth and discontinuous nonlinearities due to directional change of valve opening, friction, etc. Aside from the nonlinear nature of hydraulic dynamics, hydraulic servo systems also have large extent of model uncertainties. To address these challenging issues, a robust state-feedback controller is designed by employing backstepping design technique such that the system output tracks a given signal arbitrarily well, and all signals in the closed-loop system remain bounded. Moreover, a relevant disturbance attenuation inequality is satisfied by the closed-loop signals. Compared with previously proposed robust controllers, this paper's robust controller based on backstepping recursive design method is easier to design, and is more suitable for implementation.

On the hydrodynamic stability of a particle-laden flow in growing flat plate boundary layer

The parabolized stability equation (PSE) was derived to study the linear stability of particle-laden flow in growing Blasius boundary layer. The stability characteristics for various Stokes numbers and particle concentrations were analyzed after solving the equation numerically using the perturbation method and finite difference. The inclusion of the nonparallel terms produces a reduction in the values of the critical Reynolds number compared with the parallel flow. There is a critical value for the effect of Stokes number, and the critical Stokes number being about unit, and the most efficient instability suppression takes place when Stokes number is of order 10. But the presence of the nonparallel terms does not affect the role of the particles in gas. That is, the addition of fine particles (Stokes number is much smaller than 1) reduces the critical Reynolds number while the addition of coarse particles (Stokes number is much larger than 1) enhances it. Qualitatively the effect of nonparallel mean flow is the same as that for the case of plane parallel flows.

A Nonlinear Restoring Effect Study of Mooring System and its Application

Mooring system plays an important role in station keeping of floating offshore structures. Coupled analysis on mooring-buoy interactions has been increasingly studied in recent years. At present, chains and wire ropes are widely used in offshore engineering practice. On the basis of mooring line statics, an explicit formulation of single mooring chain/wire rope stiffness coefficients and mooring stiffness matrix of the mooring system were derived in this article, taking into account the horizontal restoring force, vertical restoring force and their coupling terms. The nonlinearity of mooring stiffness was analyzed, and the influences of various parameters, such as material, displacement, pre-tension and water depth, were investigated. Finally some application cases of the mooring stiffness in hydrodynamic calculation were presented. Data shows that this kind of stiffness can reckon in linear and nonlinear forces of mooring system. Also, the stiffness can be used in hydrodynamic analysis to get the eieenfrequencv of slow drift motions.

Extraction of Dietary Fiber from Wheat Bran and Effects of Its Additives on Viscosity-elasticity of Noodle Dough

[ Objective] The aim was to study the optimum extraction condition of dietary fiber of wheat bran and to discuss its influence on viscosity-elasticity of noodle dough with added extracts. [ Methed] Influences of a-amylase, alkaline concentration, alkaline hydrolysis time and temperature on water holding capability and swelling capacity of dietary fiber were evaluated using single-factor test and orthogonal test. Effects of added dietary fiber from wheat bran on dough absorption ratio, rupture stress of dough and creep resistance were studied. [ Result] When the hydrolysis condi-tions of wheat bran were 0.4% a-amylase at 75 ℃ for 60 rain, further alkaline conditions were 5% sodium hydroxide for 60 min at 65 ℃, dietary fi-ber exhibited fine water holding capability and swelling capacity. The addition of 3%-5% dietary fiber from wheat bran into dough had little influence on the water absorption ratio of noodle, rupture stress of dough, creep resistance and can make functional noodle with rich dietary fiber from wheat bran. [Coonclusion] The study provided reference for the comprehensive utilization of wheat bran and development of functional product.

Influences of strain softening and seepage on elastic and plastic solutions of circular openings in nonlinear rock masses

Considering the influence of strain softening, the solutions of stress, displacement, plastic softening region radius and plastic residual region radius were derived for circular openings in nonlinear rock masses subjected to seepage. The radial stress distribution curve, ground reaction curve, and relation curve between plastic softening region radius and supporting force in three different conditions were drawn respectively. From the comparisons among these results for different conditions, it is found that when the supporting force is the same, the displacement of tunnel wall considering both seepage and strain softening is 85.71% greater than that only considering seepage. The increase values of radial displacement at 0.95 m and plastic softening region radius at 6.6 m show that the seepage and strain softening have the most unfavorable effects on circular opening stability in strain softening rock masses.

Displacement Trends of Slow-moving Landslides: Classification and Forecasting

A framework is proposed to characterize and forecast the displacement trends of slow-moving landslides, defined as the reactivation stage of phenomena in rocks or fine-grained soils, with movements localized along one or several existing shear surfaces. The framework is developed based on a thorough analysis of the scientific literature and with reference to significant reported case studies for which a consistent dataset of continuous displacement measurements is available. Three distinct trends of movement are defined to characterize the kinematic behavior of the active stages of slow-moving landslides in a velocity-time plot: a linear trend-type I, which is appropriate for stationary phenomena; a convex shaped trend-type II, which is associated with rapid increases in pore water pressure due to rainfall, followed by a slow decrease in the groundwater level with time; and a concave shaped trend-type III, which denotes a non-stationary process related to the presence of new boundary conditions such as those associated with the development of a newly formed local slip surface that connects with the main existing slip surface. Within the proposed framework, a model is developed to forecast future displacements for active stages of trend-type II based on displacement measurements at the beginning of the stage. The proposed model is validated by application to two case studies.

A Lifting Line Theory for a Three-dimensional Hydrofoil

Prandtl’s lifting line theory was generalized to the lifting problem of a three-dimensional hydrofoil in the presence of a free surface. Similar to the classical lifting theory, the singularity distribution method was utilized to solve two-dimensional lifting problems for the hydrofoil beneath the free surface at the air-water interface, and a lifting line theory was developed to correct three-dimensional effects of the hydrofoil with a large aspect ratio. Differing from the classical lifting theory, the main focus was on finding the three-dimensional Green function of the free surface induced by the steady motion of a system of horseshoe vortices under the free surface. Finally, numerical examples were given to show the relationship between the lift coefficient and submergence Froude numbers for 2-D and 3-D hydrofoils. If the submergence Froude number is small free surface effect will be significant registered as the increase of lift coefficient. The validity of these approaches was examined in comparison with the results calculated by other methods.

Influence of wave and current on deep-sea mining transporting system

As a solution to the breaking of pipeline under high axial force,carbon fiber composite pipe with low density and high intensity is applied to deep-sea mining transporting system.Based on the fact that the transporting pipe is under the forces of gravity,inner liquid,buoyancy as well as hydrodynamic force,geometric nonlinear finite element theory has been applied to analyzing the transporting system.Conclusions can be drawn as follows.Under the interaction of waves and currents,node forces FX and FZ acted by the transporting pipe on the mining vehicle are less than 2 kN,which indicates that waves and currents have little influence on the spatial shape of the transporting pipe and the mining vehicle movement.On the other hand,the horizontal force acting on the mining ship could be as large as 106 830 N,which has great influence on the mining system.

大型三瓣式下环的加工制造

通过工艺手段,解决百万千瓦级转轮核心铸件大型三瓣式下环组装结合面间隙和错边问题,防止变形,保证高精度水力型线,从而满足了图纸设计要求。

Analysis and numerical simulation of dynamic effect on rock under high pressure water jet

Based on continuum mechanics and rock dynamics,analyzed the micro-struc- ture damage of rock and the impulsive effect under high pressure water jet and developed the dynamic model.Further,on the assumption of that rock was homogeneous and iso- tropic,a computational model was established based on nonlinear finite element and Arbi- trary Lagrangian-Eulerian(ALE) method.The dynamic effect impacted on rock under high pressure water jet was simulated by the dynamic contact method.The propagation of stress wave in rock was numerically simulated at different impacting velocity.The results show that the propagation velocity of stress wave is proportional to the impacting velocity of high pressure water jet.The faster the impacting velocity is,the quicker the comedown of stress wave.

Moisture effect on compressive behavior of concrete under dynamic loading

The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique "split Hopkinson pressure bar"(SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s-1. The compressive behavior of materials was measured in terms of stress-strain curves, dynamic compressive strength, dynamic increase factor(DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress-stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress-strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content.Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.