Wind-sand flow simulation and radius optimization of highway embankment under different vertical curve radius

It is of great practical value to explore the correlation between the vertical curve radius of desert highway and the increase of sand accumulation in local lines,and to select the appropriate vertical curve radius for reducing the risk of sand accumulation.In this study,three-dimensional models of desert highway embankments with different vertical curve radii were constructed,and Fluent software was used to simulate the wind-sand flow field and sand accumulation distribution of vertical curve embankments.The results show that:(1)Along the direction of the road,the concave and the convex vertical curve embankments have the effect of collecting and diverging the wind-sand flow,respectively.When the radius of the concave vertical curve is 3000 m,5000 m,8000 m,10000 m and 20000 m,the wind velocity in the middle of the vertical curve is 31.76%,22.58%,10.78%,10.53%and 10.44%,higher than that at both ends.When the radius of the convex vertical curve is 6500 m,8000 m,10000 m,20000 m and 30000 m,the wind velocity at both ends of the vertical curve is 14.06%,9.99%,6.14%,3.22%and 2.41%,higher than that in the middle.The diversion effect also decreases with the increase of the radius.(2)The conductivity of the concave and convex vertical curve embankments with different radii is greater than 1,which is the sediment transport roadbed.The conductivity increases with the increase of radius and gradually tends to be stable.When the radius of the concave and convex vertical curves reaches 8000 m and 20000 m respectively,the phenomenon of sand accumulation is no longer serious.Under the same radius condition,the concave vertical curve embankment is more prone to sand accumulation than the convex one.(3)Considering the strength of the collection and diversion of the vertical curve embankment with different radii,and the sand accumulation of the vertical curve embankment in the desert section of Wuma Expressway,the radius of the concave vertical curve is not less than 8000 m,and the radius of the convex vertical curve is not less than 20000 m,which can effectively reduce the sand accumulation of the vertical curve embankment.In the desert highway area,the research results of this paper can provide reference for the design of vertical curve to ensure the safe operation of desert highway.

A Higher-Efficient Non-Hydrostatic Finite Volume Model for Strong Three-Dimensional Free Surface Flows and Sediment Transport

In order to accurately simulate strong three-dimensional （3-D） free surface flows and sediment transport, the fully 3- D non-hydrostatic pressure models are developed based on the incompressible Navier-Stokes equations and convection-diffusion equation of sediment concentration with the mixing triangle and quadrilateral grids. The governing equations are discretized with the unstructured finite volume method in order to provide conservation properties of mass and momentum, and flexibility with practical application. It is shown that it is first-order accurate on nonuniform plane two-dimensional （2-D） grids and second-order accurate on uniform plane grids. A third-order approximation of the vertical velocity at the top-layer is applied. In such a way, free surface zero stress boundary condition is satisfied maturely, and very few vertical layers are needed to give an accurate solution even for complex discontinuous flow and short wave simulation. The model is applied to four examples to simulate strong 3-D free surface flows and sediment transport where non-hydrostatic pressures have a considerable effect on the velocity field. The newly developed model is verified against analytical solutions with an excellent agreement.

PREDICTIONS OF 3-D STRONGLY SWIRLING GAS-SOLID TWO-PHASE FLOW WITH GAS COMBUSTION

ＰＲＥＤＩＣＴＩＯＮＳＯＦ３┐ＤＳＴＲＯＮＧＬＹＳＷＩＲＬＩＮＧＧＡＳ┐ＳＯＬＩＤＴＷＯ┐ＰＨＡＳＥＦＬＯＷＷＩＴＨＧＡＳＣＯＭＢＵＳＴＩＯＮＷａｎｇＺｈｅｎｙｕ（王振宇）（ＳｈａｎｇｈａｉＷｕｊｉｎｇＴｈｅｒｍａｌＰｏｗｅｒＰｌａｎｔ）ＨｕａｎＢｏ...

Study of Nonlinear Earthquake Flow Functions and Their Application to the Space Increased Probability of Strong Earthquake (SIP)

The definition and abnormality discriminatory criteria of earthquake flow function are introduced in this paper based on the algorithm of Space Increased Probability (SIP). Nine earthquake flow functions were defined by the method. The retrospect test that applied the SIP algorithm with the nonlinear earthquake flow function to 7 earthquakes, which occurred from 1975 to 1989 in Eastern China, with a magnitude of 6 or greater depicted that 6 of the 7 strong earthquakes (86%) were located in the SIP areas, and the SIP covers about 32% of the total research time-space domain. These suggest that the R-value, an effective scale for earthquake forecast, is 54% and may imply that the nonlinear earthquake flow function introduced in this paper can be applied to the intermediate-term earthquake forecast research.

强封堵防塌型水基钻井液体系室内制备及其应用

选取目标区块进行了储层水化行为特性分析,提出了一种强封堵防塌型高性能水基钻井液体系。优选了封堵剂、降滤失剂、抑制剂与润滑剂为关键处理剂,对其流变性、封堵性、抑制性、润滑性、抗温性以及井壁稳定性进行了实验评价,并进行了现场应用测试。结果显示:基浆、3.0%磺化沥青及5%碳酸钙三者组合可实现体系滤失量最低,3%SAP+6%PAH+0.5%HB降滤失效果最佳,6%PEG和5%FH6为抑制剂与润滑剂。配制的水基钻井液体系滤失量几乎为0,页岩滚动回收率为96.99%,可以很好地起到井壁防塌稳定的效用,综合性能与油基钻井液体系相差不大。现场应用测试过程中高温高压失水量低至3.9 mL,钻井固相质量分数仅为5.29%,极压润滑系数显著低于非测试井,验证了该水基钻井液体系的实用性。

海上平台强引射放空火炬流动特性数值研究

针对一种强引射放空火炬,应用Fluent软件对辅助引射器和火炬头的流动特性进行了数值模拟研究。基本型计算表明,辅助引射器的引射系数为3.25,火炬头的引射比为0.77。正交分析表明,辅助引射器优化参数组合为:混合管道扩张角4°、喉部环空间隙7.5 mm、燃气入口直径7 mm、空气入口直径60 mm,优化结构引射系数为6.30;火炬头优化参数组合为:筒体扩张角7°、防风罩间隙207 mm、辅助引射器数量8、主放空管深度242 mm,优化结构引射比为0.89,引射性能提高16%。

强震区沟谷宽缓组合对泥石流动力学特征影响研究

岷江上游分布着大量宽缓型和窄陡型泥石流沟,沟道的宽缓和窄陡对泥石流动力学特征具有重要影响。以岷江上游宽缓型沟谷桃关沟为研究对象,采用Massflow软件模拟再现了沟谷内泥石流的动力过程,得到了“宽缓支沟+宽缓主沟”“窄陡支沟+宽缓主沟”两种组合下的泥石流动力学特征。研究表明:流域内不同级别支沟间的宽缓组合对泥石流的运移具有显著影响,这种沟间组合因素影响了泥石流的速度和泥深。“窄陡+宽缓”组合下,前期泥石流流速较大,下蚀效应明显,扩散路径长,后期多淤积;而“宽缓+宽缓”组合下,沟内泥石流的侧蚀效应更显著,加剧了沟道的演化。这两种组合下的泥石流均有堵塞河道进而发育成堰塞湖的风险。研究成果提高了关于沟道宽缓组合对泥石流运移影响的认识,可为沟谷类泥石流危险性评价提供参考。

A BLOW-UP CRITERION FOR COMPRESSIBLE VISCOUS HEAT-CONDUCTIVE FLOWS

We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.

Comparative evaluation of concrete sand-control fences used for railway protection in strong wind areas

Concrete-plate fences have been widely adopted for windblown sand control and mitigation along railways.However,the inclination angles of inserting the concrete plate with respect to the vertical direction,i.e.,straight or obliquely inserted concrete plates(SIP or OIP),significantly influence the efficiency of sand-control.This study performs a comparative evaluation of the SIP and OIP sand-control fences using wind tunnel testing and field monitoring data collected from the Lanzhou–Wulumuqi High-Speed Railway Project.The results show that the fence’s ability to reduce the wind speed and the sand-retaining efficiency gradually weakens with the increasing wind speed.Compared with the SIP fence,the OIP fence has a better wind speed reduction capability,stronger ability to capture fine particles below the top of the fence;it is more efficient for sand-retaining and induces stronger eddy intensity.Generally,the wind tunnel test and field monitoring results are consistent,whereas wind tunnel tests incline to overestimate wind speed reduction and sand-control efficiency.The study also finds that the aeolian sand accumulated around the fence can weaken the protection efficiency,and hence cleaning the aeolian sand accumulated around the fence should be done periodically to ensure the designed functions.

Dynamic enhanced multi-slice spiral CT in evaluation of blood flow patterns of solitary pulmonary nodules with enhancement

Objective To investigate the methods of dynamic enhanced multi-slice spiral CT in evaluation of blood flow patterns of solitary pulmonary nodules (SPNs) with enhancement. Methods Seventy-eight patients with SPNs (≤4 cm) with strong enhancement underwent dynamic multi-slice spiral CT (Marconi Mx8000) scan before and after contrast enhancement by injecting contrast material with a rate of 4 mL/s. For the 40 patients in protocol one, one scan was obtained every 2 seconds during 15--45 and 75--105 seconds after injection, while for the 38 patients in protocol two, one scan was obtained every 2 seconds during 11--41 and 71--101 seconds. For all the patients, one scan was obtained every 30 seconds during 2--9 minutes. The section thickness was 2.5 mm for lesions ≤3 cm and 5 mm for lesions >3 cm. Standard algorithm was used in the image reconstruction. Precontrast and postcontrast attenuation on every scan was recorded. The perfusion, peak height, ratio of peak height of the SPN to that of the aorta and mean transit time were calculated. Results The peak height, perfusion, ratio of peak height of the SPN to that of the aorta and mean transit time in malignant SPNs were 34.85 Hu±10.87 Hu, 30.37 ml/(min·100 g)±11.14 ml/(min·100 g), 13.78%± 3.96% , 14.19 s±6.19 s respectively in protocol one, while those in protocol two were 36.62 Hu±10.75 Hu, 30.01 ml/(min·100 g)±8.10 ml/(min·100 g), 14.70 %±4.71%, 13.91 s±4.82 s respectively. No statistically significant differences were found between the peak height (t= 0.673, P=0.503), perfusion (t= 0.152 , P=0.880), ratio of peak height of the SPN to that of the aorta (t= 0.861, P=0.393) and mean transit time (t= 0.199, P=0.843) in malignant SPNs measured in protocol one and those measured in protocol two. All mean transit time in protocol two (36/36) were obtained, but only part of them (25/32) were obtained in protocol one. Conclusion Dynamic enhanced multi-slice spiral CT is a non-invasive method for quantitative evaluation of blood flow patterns of SPNs with enhancement and scans beginning at 11 seconds after injection of contrast material is suggested.

Simulation of faceted dendrite growth of non-isothermal alloy in forced flow by phase field method

Numerical simulation based on a new regularized phase field model was presented to simulate the dendritic shape of a non-isothermal alloy with strong anisotropy in a forced flow. The simulation results show that a crystal nucleus grows into a symmetric dendrite in a free flow and into an asymmetry dendrite in a forced flow. As the forced flow velocity is increased, both of the promoting effect on the upstream arm and the inhibiting effects on the downstream and perpendicular arms are intensified, and the perpendicular arm tilts to the upstream direction. With increasing the anisotropy value to 0.14, all of the dendrite arms tip velocities are gradually stabilized and finally reach their relative saturation values. In addition, the effects of an undercooling parameter and a forced compound flow on the faceted dendrite growth were also investigated.

A new numerical approach of coupled modeling for solid deformation and gas leak flow in multi-coal-seams

From the viewpoint of interaction mechanics for solid and gas, a coupled mathematical model was presented for solid coal/rock deformation and gas leak flow in parallel deformable coal seams. Numerical solutions using the SIP (Strong Implicit Proce- dure) method to the coupled mathematical model for double parallel coal seams were also developed in detail. Numerical simulations for the prediction of the safety range using protection layer mining were performed with experimental data from a mine with potential danger of coal/gas outbursts. Analyses show that the numerical simulation results are consistent with the measured data in situ.

Relationship between crustal magnetic anomalies and strong earthquake activity in the south segment of the China North-South Seismic Belt

The south segment of the China North-South Seismic Belt is located in the southeast margin of the Qinghai Tibet Plateau.This region is characterized by the frequent seismic activity in Chinese mainland.In this paper,the geomagnetic field model NGDC-720 and the data of terrestrial heat flow are used to investigate the distribution of crustal magnetic anomalies,the depth of Curie surface,and the characteristics of the crustal thermal structure in the south segment of the North-South Seismic Belt.The distribution characteristics of the vertical component AZ and the magnetic declination AD in the area with earthquakes over a magnitude of 6 and their aftershocks since 1970 are focused on.The results show that the earthquakes are mainly observed in the area of negative magnetic anomaly or the strong and weak transition zone.It especially shows in the AD.The Curie surface in the study area varies significantly,ranging from 20.8 to 31 km.The uplift area of the Curie surface is consistent with the high-value area of terrestrial heat flow.The high geothermal area corresponds to the strong earthquake activity area.The focal depth of most strong earthquakes is shallower than the depth of the Curie surface.The strong earthquakes mainly occur in the deep-shallow transition zones of the Curie surface.The results can be used as a reference for strong earthquake prediction in this area.

Plastic-Flow Waves (“Slow-Waves") and Seismic Activity in Central-Eastern Asia

The results inferred from experiments with analogue models carried out previously have shown that two types of plastic-flow waves, “fast-waves" and “slow-waves", are induced in the lower lithosphere (including the lower crust and lithospheric mantle) under driving at plate boundaries and both of them are viscous gravity waves formed by the superposition of major and subsidiary waves. The major waves are similar to solitary waves and the subsidiary waves are traveling waves. The plastic-flow waves in the lower lithosphere control seismic activities in the overlying seismogenic layer and result in the distribution of earthquakes along the wave-crest belts. “Fast-waves" propagated with velocities of orders of magnitude of 100～102km/a have been verified by wave-controlled earthquake migration, showing the “decade waves" and “century waves" with the average periods of 10.8 and 93.4 a, respectively, which originate from the Himalayan driving boundary. According to the recognition of the patterns of the belt-like distribution of strong earthquakes with M S≥7.0, it is indicated further in this paper that the “slow-waves" with velocities of orders of magnitude of 100～101 m/a also originated under compression from the Himalayan driving boundary. Strong earthquakes with M S≥7.0 are controlled mainly by subsidiary waves, because the major waves with a duration of up to 106 a for each disturbance cannot result in the accumulation of enough energy for strong earthquakes due to the relaxation of the upper crust. The subsidiary waves propagate with an average wave length of 445 km, velocities of 0.81～2.80 m/a and periods of 0.16～0.55 Ma. The wave-generating time at the Himalayan driving boundary is about 1.34～4.59 Ma before present for the “slow-waves", corresponding to the stage from the Mid Pliocene to the Mid Early-Pleistocene and being identical with one of the major tectonic episodes of the Himalayan tectonic movement. It is shown from the recognition of the wave-controlled belts of strong earthquakes that two optimal patterns of wave-crest belts originated simultaneously from the eastern and western segments of the Himalayan arc, respectively. The overlap of wave-crest belts of these two systems is responsible for the relative concentration of energy and forms the seismic-energy-background zones for strong earthquakes with M S≥7.0.

The Realization of a Strong Trade Power and China’s Direct Investment in SCO Countries

China’s path to becoming a strong trade power can be divided into three levels:the micro level of promoting factor cultivation,the meso level of achieving industrial dominance,and the macro level of participating in the establishment of the world system.As a feature of globalization,factor flow is the foundation and key to achieve the above three-level goals.In the first stage of reform and opening-up,China complied with the globalization characteristics of factor flow and gathered a large number of capital factors.It is now the second stage of reform and opening-up;that is,the stage of export-oriented investment.International investment may help in the path to become a strong trade power,or it may become an obstacle.The maximization of benefits and evasion of disadvantages are influenced by the grasp of investment risks.Therefore,special attention should be paid to identifying potential risks and controlling risks.

长江口白茆沙河段南强北弱格局变化特征研究

近年来白茆沙汊道“南强北弱”态势持续增强,南水道主槽和近岸河床冲刷明显,日益威胁水下岸坡稳定与附近码头安全。通过对白茆沙汊道演变态势与分流比变化特征展开分析,进而对白茆沙汊道“南强北弱”分流格局变化及原因进行了系统研究。研究认为:白茆沙汊道“南强北弱”格局增强的态势是白茆沙汊道历年来周期性演变中某一阶段的表现形式;鉴于不同方法计算的汊道分流比存在差异,故用分流比表征汊道强弱时,应选用同一类型的值进行比较;深水航道一期整治工程实施遏制了白茆沙冲刷后退的态势,改变了该河段周期性演变的模式,有利于河势稳定;在现有水情、工情及河势条件下,白茆沙汊道“南强北弱”的格局变化将趋缓。

考虑地震动持时效应的结构拟静力试验加载制度研究

历次大地震震害表明,地震动持时对工程结构累积损伤有显著影响,长持时地震动作用下结构损伤明显加重,因此确定地震动持时对结构地震反应及损伤的定量影响成为近来一个热门研究课题。拟静力试验是模拟结构地震反应的重要手段,但目前其加载制度很少考虑地震动持时的影响。鉴于此,文中建立了7种周期、4种目标延性、2种本构模型共计56个单自由度体系结构,以114对长、短持时地震动为输入,计算了其位移反应时程,并通过雨流计数法统计分析了自振周期、目标延性及本构模型等参数和结构往复循环次数之间的关系。结果表明,结构非弹性循环圈数与周期和目标延性相关性较强,而结构振幅分布与周期相关性较小,但与目标延性相关性较强。根据统计结果拟合了不同周期结构在长持时地震动作用下的位移振幅分布公式,进而提出考虑地震动持时效应的结构拟静力试验加载制度确定方法,结果可供确定结构拟静力试验加载制度参考。

基于ANSYS的新组合型单螺杆挤出机特性研究

针对普通单螺杆挤出机剪切混合模式单一、工作性能差等问题,研究设计一种新组合型单螺杆。采用SolidWorks建模,ANSYS/CFX有限元分析和对比试验的方法;形成新组合型单螺杆流道整体压力差高于传统单螺杆1.22 MPa左右,物料在进出强剪切段过程中有回流产生,强剪切段物料输送速度较传统单螺杆加快0.012 m/s左右的结果;得出新组合型单螺杆挤出机在80-160 r/min的转速下,物料停留时间较传统单螺杆挤出机缩短5%-12%的试验结论。研究为高性能单螺杆挤出机的优化创新提供理论依据。

强震区沟谷型泥石流峰值流量预测研究及应用

强震区次生泥石流灾害演化规律与发展趋势受地震“后效应”影响显著,与震前相比,其峰值流量增长数倍,泥石流规模增大显著,对震区沟谷型泥石流针对性防治设计提出新挑战。基于四川汶川强震区泥石流案例,采用因子回归分析方法研究流域特征参数与峰值流量的内在关系,建立泥石流峰值流量多元预测模型。结果表明:预测模型解决了原始变量共线性导致的信息叠加问题,模型拟合优度R^(2)=0.94,预测精度显著提升;采用预测模型对研究区32条泥石流沟的峰值流量阈值进行预测,得出强震区泥石流动力特性分布规律与泥石流规模演化特征,在此基础上定义了震区“特大型高位远程型泥石流”的特征参数。

大变形柔性管道两相流流致振动研究

针对柔性管道内段塞流引起的结构大变形流致振动问题,本文采用分区强流固耦合方法建立了面向大变形两相流输运管道的双向流固耦合数值计算模型.基于流体体积法对气液两相流动界面进行追踪并结合任意拉格朗日-欧拉(ALE)动网格方法考虑流体域网格变形,同时采用有限元方法建立了柔性管道动力学模型,根据流体和管道壁面的相互作用构建强流固耦合计算模型.研究表明,在两相流作用下柔性管道的振动主要以类似一阶和二阶振动模态响应为主且会发生模态切换;模态切换与管内的液塞长度、液塞流动频率以及气液塞在管内的轴向分布有关;管道的大变形振动促进了短气塞的融合并显著改变了液塞的长度和频率,进而影响管道的振动和流型转变界限.