Sedimentary characteristics and internal architecture of a river-dominated delta controlled by autogenic process:implications from a flume tank experiment

Autogenic processes are widely found in various sedimentary systems and they play an important role in the depositional evolution and corresponding sedimentary architecture.However,autogenic processes are often affected by changing allogenic factors and are difficult to be identified and analyzed from modern and ancient records.Through the flume tank experiment under constant boundary conditions,the depositional process,evolution principles,and the sedimentary architecture of a river-dominated delta was presented,and a corresponding sedimentary architecture model was constructed.The evolution of river-dominated delta controlled only by autogenic process is obviously periodic,and each autogenic cycle can be divided into an initial progradational stage,a middle retrogratational stage,and a late aggradational–progradational stage.In the initial progradational stage,one feeder channel incised into the delta plain,mouth bar(s)was formed in front of the channel mouth,and small-scale crevasse splays were formed on the delta plain.In the middle retrogradational stage,the feeder channel was blocked by the mouth bar(s)which grew out of water at the end of the initial stage,and a set of large-scale distributary splay complexes were formed on the delta plain.These distributary splay complexes were retrogradationally overlapped due to the continuous migration of the bifurcation point of the feeder channel.In the late aggradational–progradational stage,the feeder channel branched into several radial distributary channels,overlapped distributary channels were formed on the delta plain,and terminal lobe complexes were formed at the end of distributary channels.The three sedimentary layers formed in the three stages constituted an autogenic succession.The experimental delta consisted of six autogenic depositional successions.Dynamic allocation of accommodation space and the following adaptive sediments filling were the two main driving factors of the autogenic evolution of deltas.

Water-Tank Experiment on the Thermal Circulation Induced by the Bottom Heating in an Asymmetric Valley

Water tank experiments were carried out to investigate the thermal convection due to the bottom heating in an asymmetrical valley under neutral and stably stratified approach flows with the Particle Image Velometry (PIV) visualization technique. In the neutral stratification approach flow, the ascending draft induced by bottom heating is mainly located in the center of the valley in calm ambient wind. However, with ambient wind flow, the thermal convection is shifted leeward, and the descending draft is located on the leeward side of the valley, while the ascending draft is located on the windward side. The descending draft is minorly turbulent and organized, while the ascending draft is highly turbulent. With the increase of the towing speed, the descending and ascending drafts induced by the mechanical elevation begin to play a more dominant role in the valley flow, while the role of the thermal convection in the valley airflow becomes limited. In the stable stratification approach flow, the thermal convection is limited by the stable stratification and no distinct circulation is formed in calm ambient wind. With ambient wind, agravity wave appears in the upper layer in the valley. With the increase of the ambient wind speed, a gravity wave plays an important role in the valley flow, and the location and intensity of the thermal convection are also modulated by the gravity internal waves. The thermal convection has difficulty penetrating the upper stable layer. Its exchange is limited between the air in the upper layer and that in the lower layer in the valley, and it is adverse to the diffusion of pollutants in the valley.

Hydrodynamic Characteristics of the Biplane-Type Otter Board with the Canvas Through Flume−Tank Experiment

Hydrodynamic characteristics of a biplane-type otter board,equipped with nylon canvas of 2 mm in thickness was investigated through flume-tank experiment in this study.A series of predesigned structures with different gap-chord ratios G/c(0.75,0.90,1.05),stagger anglesθ(30°,45°,60°),and proportions of flexible area relative to the whole wing areaƒr(0,55%,65%,75%),at an aspect ratio of 2.0 and a camber ratio of 15%,were experimentally carried out.The results showed the solution referring to the usage of flexible canvas replacing part of rigid structure for the biplane-type otter board was efficient for the trawling in the middle or shallow water area.The improvement of lift and stability for the biplane-type otter board was concluded,and drag of the structure was reduced by 1.9%atƒr=55%.In addition,the coefficient of variation of the lift and drag coefficient at different current velocities were 2.69%and 2.28%,respectively,which was smaller than those at relatively large proportion of the flexible area.Compared with the other tested structures,the frame-type flexible structure with the gap-chord ratio of 0.9 and a stagger angle of 45°and the proportion of the flexible area of 55%,performed best,and its drag was reduced by 5.72%and lift increased by 4.8%,compared with the rigid biplane-type otter board at the angles of attack from 18°to 28°.

Nepheloid layer generation by gas eruption:unexpected experimental results

Knowledge of nepheloid layers is important to improve the understanding of physical,geological,and sedimentary processes from continental shelf to abyssal environments.We had not tried to study the nepheloid layers in a hydrate-associated tank until unexpected results occurred.Tank experimental results show that gas eruptions triggered intermediate nepheloid layers.Thus,we proposed a new mechanism of intermediate nepheloid layer generation by eruptions.The intermediate nepheloid layers were generated in uniform-density fluid,which indicated that stratified fluid is not a necessary condition for intermediate nepheloid layers.Sufficient space for advection and an oblique slope for detachment are the key ingredients for intermediate nepheloid layer generation by eruptions.Our experiments also offer a new experimental evidence for bottom nepheloid layer generation by earthquakes.Given the scale effects of laboratory experiment,it is important to determine whether submarine volcanic eruption or hydrate-associated venting causes intermediate nepheloid layer in the nature.

Effects of Perforated Baffle on Reducing Sloshing in Rectangular Tank:Experimental and Numerical Study

A liquid sloshing experimental rig driven by a wave-maker is designed and built to study liquid sloshing problems in a rectangular liquid tank with perforated baffle. A series of experiments are conducted in this experimental rig to estimate the free surface fluctuation and pressure distribution by changing external excitation frequency of the shaking table. An in-house CFD code is also used in this study to simulate the liquid sloshing in three-dimensional （3D） rectangular tank with perforated baffle. Good agreements of free surface elevation and pressure between the numerical results and the experimental data are obtained and presented. Spectral analysis of the time history of free surface elevation is conducted by using the fast Fourier transformation.

Migration of Infiltrated NH_4 and NO_3 in a Soil and Groundwater System Simulated by a Soil Tank

The infiltration of water contaminants into soil and groundwater systems can greatly affect the quality of groundwater. A laboratory-designed large soil tank with periodic and continuous infiltration models, respectively, was used to simulate the migration of the contaminants NH4 and NO3 in a soil and groundwater system, including unsaturated and saturated zones. The unsaturated soil zone had a significant effect on removing NH4 and NO3 infiltrated from the surface water. The patterns of breakthrough curves of NH4 and NO3 in the unsaturated zone were related to the infiltration time. A short infiltration time resulted in a single sharp peak in the breakthrough curve, while a long infiltration time led to a plateau curve. When NH4 and NO3 migrated from the unsaturated zone to the saturated zone, an interracial retardation was formed, resulting in an increased contaminant concentration on the interface. Under the influence of horizontal groundwater movement, the infiltrated contaminants formed a contamination-prone area downstream. As the contaminants migrated downstream, their concentrations were significantly reduced. Under the same infiltration concentration, the concentration of NO3 was greater than that of NH4 at every corresponding cross-section in the soil and groundwater tank, suggesting that the removal efficiency of NH4 was greater than that of NO3 in the soil and groundwater system.

Numerical and Experimental Studies on Flow and Pollutant Dispersion in Urban Street Canyons

In this study numerical simulations and water tank experiments were used to investigate the flow and pollutant dispersion in an urban street canyon. Two types of canyon geometry were tested. The studies indicate that in a step-up notch canyon （higher buildings on the downstream side of the canyon）, the height and shape of the upstream lower buildings plays an important role in flow pattern and pollutant dispersion, while in a step-down notch canyon （lower buildings on the downstream side）, the downstream lower buildings have little influence. The studies also show that the substitution of tall towers for parailelepiped buildings on one side of the canyon may enhance the street ventilation and decrease the pollutant concentration emitted by motor vehicles.

基于正交实验法的储罐泄漏对邻近建筑影响研究

为准确评估气相危险化学品从储罐中意外泄漏对周边环境的影响,以邻近建筑为研究对象,结合正交实验法,针对不同的考察指标,对影响危险气体在周边区域扩散的4个关键因素进行分析。研究结果表明:泄漏位置仅对建筑迎风面危险气体极值体积分数有较为明显的影响,不同泄漏位置造成的差异能达到23.2%。建筑密度的增加导致建筑区域面平均体积分数增加30%以上,而建筑区域危险气体极值体积分数分别降低了9.4%和30.4%。建筑与储罐组间距和建筑密度对于邻近建筑的影响强度(以极差来评价),是泄漏位置和气体种类的1.5~10倍。研究结果可为化工园区安全设计、合理规避事故风险提供参考。

某乘用车燃油箱强度仿真及试验研究

针对乘用车燃油箱这一重要的安全部件,在其前期设计阶段进行考虑流固耦合的有限元分析发现,前部和后部跌落存在应变超标现象。对其风险部位进行结构改进,强度仿真显示,等效塑性应变最大值相比改进前分别减少44.7%和33.3%,跌落试验显示均无泄漏和破裂发生,满足设计要求。结果表明,基于有限元分析的仿真和试验为燃油箱的开发提供了科学依据,可有效提升产品开发效率并降低试验成本。

铁路罐车封头冷冲压成形试验研究

通过对封头成形工艺的对比分析,根据铁路罐车封头需求量大、成形质量要求高的特点,制定了厚壁封头冷冲压成形工艺。通过试验研究的方法对EHA 3000×22(19)-Q345R GB/T 25198厚板冷冲压封头成形前、后的外形尺寸、壁厚、力学性能等变化规律进行了分析研究。对封头成形前后的各项试验数据进行对比分析,掌握了厚壁封头冷冲压的成形规律;通过5组封头热处理试验掌握了热处理对冷成形封头性能的影响规律,提高了冷冲压封头的性能,确保了冷冲压封头的成形质量,保证了铁路罐车的运行安全。

Research of refrigeration system for a new type of constant temperature hydraulic tank

Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of semiconductor refrigeration and establishes a heat transfer model. Semiconductor cooler on piping refrigeration is simulated,and influence of the parameters on the outlet temperature,such as pipe pressure difference of inlet and outlet,pipe length,pipe radius,are gotten,and then hydraulic tank semiconductor refrigeration system is proposed. The semiconductor refrigeration system can control temperature at 37 ± 1°C.

Weld Models Incorporating the HAZ Phase Transformation Effects, Comparison between Experimental and Numerical Results

Numerical simulations of a representative test of welding process are presented in this paper. A French vessel steel, which involves metallurgical phase transformations in solid state is considered in this work. The aim is to validate the thermal-metallurgical-mechanical models taking into account the metallurgical transformations in the finite element codes Sysweld (Framasoft) and Code Aster (EDF). The test is performed on a thin disc submitted to a thermal cycle loading by means of a CO2 laser beam, which leads to metallurgical phase transformations. The thermal, metallurgical and mechanical numerical results have been compared to the experimental results (temperatures, sizes of transformed zones, displacements and residual stresses and strains). The main objective of the numerical analysis is to have some results which enable to give some indications on the ability of the numerical codes to describe the observed phenomena. For that, it is necessary to simulate accurately the thermo-metallurgical history. The comparison of experimental results with the numerical ones leads to some interesting orientations related to the capacities of the considered models to describe the observed phenomena.

民用建筑用毛细管相变蓄能罐性能的实验研究

随着民用建筑领域谷电利用和太阳能热利用的广泛推进,相变蓄能罐的开发和应用变得尤为关键。本工作经相变蓄能装置内部传热的理论分析,设计了以高效毛细管换热装置为核心部件的民用建筑相变蓄能罐,搭建了相变蓄能罐性能测试实验系统,记录了工业相变材料的实时温度响应数据,探究了冷热水进口温度、流量及流向对相变蓄能罐热性能的影响。研究结果表明:同进温、同流量下流动介质逆重力流动的换热量是顺重力流动的1.1~1.2倍。流量变化在蓄热阶段占主导,温度变化对放热阶段影响较大,而小流量工况下,出水温度的持续稳定性更好。对于“蓄热快且容量大、放热慢且水温高”的功能需求,蓄热阶段工质入口温度70~75℃适宜,毛细管内工质流速推荐0.025~0.035 m/s。放热阶段毛细管内工质流速建议0.020 m/s以内。同时在实际使用中,30℃、85 L/h出水工况下单台蓄热2次即可满足至少20 m2房间1天的间歇供暖需求,和至少3人次的淋浴需要。本工作为家用蓄能罐的工程应用设计、评价提供参考依据。

挡板结构与充液率对液体晃动的影响

箱体晃动会使储液箱内液体的自由表面发生飞溅现象,而液体在储液箱内的飞溅会导致壁面受到高度局部冲击力,造成储液箱的结构损坏。为了研究储液箱内自由液面晃动规律,避免储液箱内液体晃动带来的风险,搭建了液体晃动模拟实验平台,模拟挡板固度比和储液箱内自由液面高度对储液箱内液体晃动的影响。结果表明:挡板固度比增大、储液箱内自由液面高度降低可以显著降低由于储液箱内液体自由表面的飞溅产生的壁面局部压力。研究结果为储液箱的结构设计和优化提供理论依据。

融合CFD方法的搅拌反应器气液传质实验教学

搅拌反应器气液传质实验是《化学反应工程》的基础实验,主要通过对搅拌反应器内的气液传质特性进行测定,并通过关联式回归得到诸因素对传质系数的定量影响规律。但在传统的实验教学中,学时及实验测试技术的限制使得无法直接获取反应器内气液两相流的流场结构等影响传质特性相关信息。计算流体力学(CFD)方法可以从定性和定量角度揭示流场结构、气体分布以及气液传质等特性,并具有可视化、计算效率高等优点。将CFD方法与气液搅拌反应器传质实验教学融合,可加深学生对搅拌反应器内气液分散及传质机理的理解,培养学生解决化学工程问题的高阶能力。

基于热管的轻量化液压油箱散热设计与试验研究

为强化轻量化液压油箱的散热能力,基于传热学原理,利用热管高效传热的特性,配合多层螺旋折流板,设计了一种储油散热一体化的轻量化液压油箱,完成了样机加工和试验台的搭建。以样机散热功率和总传热系数为研究目标,探究了不同冷却风量、加热温度和水流量对油箱散热性能的影响,针对试验中的新发现进行了样机改进试验。结果表明,在一定范围内增加冷却风量、提升加热温度和水流量均能强化油箱的散热性能。在研究工况范围内,样机最高散热功率达到了1.13 kW,散热功率密度为22 kW/m^(3)。

半圆管挡板搅拌槽内的固液悬浮

为了提高固液悬浮性能,设计了一种半圆管挡板搅拌槽。采用数值模拟和试验测试相结合的方法,研究了半圆管挡板Rushton桨搅拌槽内石英砂—水的混合特性,分析了固液悬浮特征、固相浓度分布和功率消耗情况,并与标准平直挡板搅拌槽内的悬浮性能进行了对比。结果表明,同一搅拌转速时,半圆管挡板能改善悬浮性能,低固含率(5%)时效果更好。整体而言,半圆管挡板搅拌时石英砂的浓度分布比标准平直挡板搅拌时均匀,而且功率准数低13%左右,节能效应明显。研究结果为半圆管挡板的工业应用奠定了基础。

固液搅拌槽测量技术研究进展

固液搅拌槽是化工操作过程中最常见的单元操作之一。固液搅拌槽中的流场特性以及固相分布特性是优化设计搅拌槽的关键参数。文章对固液搅拌槽的流场测试技术进行分析概述,包括粒子图像测速(PIV)技术和粒子追踪测速(PTV)技术,也进一步探讨分析了固液搅拌槽的固相含率测试技术,包括视觉观察法、导电探针法、光学探针法、取样分析法以及电阻断层扫描成像法等。

箱涵式出水流道设计参数对泵装置性能的影响研究

为了研究箱涵式出水流道对泵装置水力性能的影响,采用DOE参数设计和CFD数值计算方法,研究箱涵式出水流道长度、宽度和高度3个设计参数对泵装置水力性能的影响,得到25个不同参数出水流道方案的CFD计算结果。研究表明,箱涵式泵装置出水流道高度对效率的影响最大,宽度对效率的影响次之,而流道长度对效率的影响最小。其中,方案11箱涵式泵装置效率最高,达到73.64%;最高效率与最低效率方案差别达到5.02%。流道宽度越宽、流道高度越高,可使导叶出来的水流扩散更充分,同时可以回收更多速度环量,进而提高泵装置的运行效率。研究结果可为提高箱涵式泵装置的运行效率提供参考。

非能动安全壳热量导出蒸汽排放装置实验研究

为了解决“华龙一号”非能动安全壳热量导出系统运行时水箱内蒸汽排放的问题,本文通过研究“华龙一号”的非能动安全壳热量导出系统的蒸汽排放装置,在理论分析的基础上,设计并开展了蒸汽排放装置的性能实验,提出蒸汽排放装置设计的关键要求,以指导工程项目中非能动安全壳热量导出系统蒸汽排放装置的设计。本文可为华龙系列后续工程中蒸汽排放装置的研究和设计提供指导和支持。