Particle characteristics and rheological constitutive relations of high concentration red mud

Red mud has relatively small solid particles （d50= 13.02 μm） and will flow in paste form under high pressure during pipeline transport. Red mud belongs to a two-phase flow of materials with high viscosity and a high concentration of non-sedimentation, homogeneous solid-liquids. It is difficult to test its rheological properties under atmospheric pressure. Measurements such as rotational viscometry can not reflect the real state of the material when it is flowing in a pipe. Tested rheological parameters are somewhat higher than the actual values. In our investigation, grain shape, distinctive modality and grain size distribution of red mud were tested. Based on the principle of tube measurement, rheological experiments on red mud at different concentrations were carried out by using our independently developed tube-type pressure theology test facility, and obtained constitutive equations. We conclude that red mud behaves as non-Newtonian pseudo-plastic fluid in pipe flows. Its consistency and power-law indices vary considerably with different concentrations.

Impact pressure of debris flow on beam dam

The use of open-type check dams in mountainous areas has become common practice in order to mitigate the effects of debris flow and extend the service life of engineering structures.The beam dam,a common debris flow control system,has received less attention in research on the impact process of debris flow and check dams compared to solid check dams.Additionally,the estimation of impact pressure in debris flow primarily considers debris flow characteristics,without taking into account the influence of geometric characteristics of the transmission structure.To better understand the impact process of debris flow on beam dams,a series of small-scale debris flow impact tests were conducted in a model flume.Key parameters,including velocity,depth,and impact pressure,were measured.The results show that the maximum impact pressure of debris flow is affected by both the characteristics of the debris flow and the relative opening size of the beam dam.Due to flow and edge occlusion in the middle of the beam dam,the discharge of debris flow is enhanced,resulting in a longer impact process and higher maximum impact pressure.Based on these findings,a calculation model of the maximum impact pressure of debris flow at the midpoint of the middle beam is proposed,which can be used to estimate the impact of debris flow on the discharge part of the beam dam.

Comparison between Diastolic Subendocardial Tissue Pressures Measured Directly or Calculated from Pressure-Flow Relations

Changes in intramyocardial tissue pressure modulate the relationship between coronary pressure and flow during the cardiac cycle. The present study compared the relation between measured and calculated diastolic subendocardial tissue pressure and coronary pressure at zero flow in anesthetized dogs after modulation of either coronary sinus (i.e. Fogarty catheter) or left ventricular intracavity (i.e. volume loading) pressure. Experiments were conducted in anesthetized, instrumented dogs;coronary pressure flow relations were constructed during pharmacologic vasodilatation and intramyocardial tissue pressure was measured using micromanometer pressure sensors. Elevated coronary sinus pressures did not affect subendocardial pressure-flow relations signifying that diastolic tissue pressure within this layer is the effective coronary back pressure. Higher left ventricular intracavity pressure did not affect either diastolic subendocardial tissue pressure or pressure flow relations within this layer. Results show a direct linear relation (y = 1.106x - 0.652;r2 = 0.59. P = 0.001) between measured and calculated diastolic subendocardial tissue pressure and coronary pressure at zero-flow over a wide range of pressures after either LV systemic or coronary sinus pressure modulation. Knowledge of back pressure in the subendocardium is useful for the evaluation of efficacy of cardiac interventions on myocardial perfusion particularly at the level of the microcirculation.

High-precision nonisothermal transient wellbore drift flow model suitable for the full flow pattern domain and full dip range

A reliable multiphase flow simulator is an important tool to improve wellbore integrity and production decision-making.To develop a multiphase flow model with high adaptability and high accuracy,we first build a multiphase flow database with 3561 groups of data and developed a drift closure relationship with stable continuity and high adaptability.Second,a high-order numerical scheme with strong fault capture ability is constructed by effectively combining MUSCL technology,van Albada slope limiter and AUSMV numerical scheme.Finally,the energy equation is coupled into the AUSMV numerical scheme of the drift flow model in the form of finite difference.A transient non-isothermal wellbore multiphase flow model with wide applicability is formed by integrating the three technologies,and the effects of various factors on the calculation accuracy are studied.The accuracy of the simulator is verified by comparing the measurement results with the blowout experiment of a full-scale experimental well.

Modeling of Soybean Plant Sap Flow

Soybean (Glycine max. (L.) Merr.) sap flow during the growth stages in relation to soil moisture, nutrition, and weather conditions determine the plant development. Modeling this process helps to better understand the plant water-nutrition uptake and improve the decisions of efficient irrigation management and other inputs for effective soybean production. Field studies of soybean sap flow took place in 2017-2021 at Marianna, Arkansas using heat balance stem flow gauges to measure the sap flow during the reproductive growth stages R3-R7. Plant water uptake was measured using the lysimeter-container method. The uniform sap flow-based hydraulic system in the soil-root-stem-leaf pathway created negative water tensions with osmotic processes and water surface tensions in stomata cells as water evaporation layers increase are the mechanism of the plant water uptake. Any changes the factors like soil water tension, solar radiation, or air relative humidity immediately, within a few seconds, affect the system’s balance and cause simultaneously appropriate reactions in different parts of the system. The plant water use model was created from plant emergence, vegetative to final reproductive growth stages depending on soil-weather conditions, plant morphology, and biomass. The main factors of the model include solar radiation, air temperature, and air relative humidity. The effective sap flow uptake occurs around 0.8 KPa VPD. Further research is needed to optimize the model’s factors to increase the plant growth dynamics and yield productivity.

Study of the Flow Mechanism of Wind Turbine Blades in the Yawed Condition

The computational fluid dynamics method was used to simulate the flow field around a wind turbine at the yaw angles of 0°,15°,30°,and 45°.The angle of attack and the relative velocity of the spanwise sections of the blade were extracted with the reference points method.By analyzing the pressure distribution and the flow characteristics of the blade surface,the flow mechanism of the blade surface in the yawed condition was discussed.The results showed that the variations of the angle of attack and the relative velocity were related to the azimuth angle and the radius in the yawed condition.The larger the yaw angle was,the larger the variation was.The pressure distribution in the spanwise sections was affected by both the angle of attack and the relative velocity.The angle of attack was more influential than the relative velocity.At the same yaw angle,when the angle of attack decreased,the c_(p)∼x/c curve shrunk inward and the lift force decreased.The larger the yaw angle was,the more obvious the shrink was.The effect of the yaw on the blade root region was higher than its effect on the blade tip region.

Numerical Investigation on the Secondary Flow Control by Using Splitters at Different Positions with Respect to the Main Blade

In turbomachinery,strong secondary flow can produce significant losses of total pressure near the endwall and reduce the efficiency of the considered turbomachine.In this study,splitters located at different positions with respect to the main blade have been used to reduce such losses and improve the efficiency of the outlet guide vane(OGV).Three different relative positions have been considered assuming a NACA 65-010 profile for both the main blade and the splitter.The numerical results indicate that splitters can effectively reduce the total pressure loss by suppressing the secondary flow around the main blade,but the splitters themselves also produce flow losses,which are caused by flow separation effects.

基于工况特征的高速插齿机静压主轴润滑特性研究

针对高速插齿机静压主轴在实际工况特征下存在润滑特性不明晰的问题,以摩擦学和流体力学理论为基础,采用有限元仿真法建立不同受载状态下的静压主轴流体仿真模型及流固耦合模型,基于实际工况特征探究不同工况参数下静压主轴的润滑特性变化规律。结果表明,油膜承载力、主轴轴套变形量及黏性阻力随径向增大而增加,而油膜刚度则是随径向载荷增大先减小后增加。轴套最大变形位置随径向载荷增大而不同。在相同径向载荷下,主轴冲程速度对油膜承载力基本无影响而黏性阻力随冲程速度增大而增加。增大供油压力可显著提高静压主轴承载性能但轴套最大变形量也有明显增大,同时会改变油液流动方向进而加剧油膜黏性剪切应力集中现象,最终使得应力集中区域油膜破裂出现润滑失效现象。

震后给水管网服务性能的模糊评价方法

基于震后城市给水管网水力分析模型和给水管网系统服务性能准则,引入模糊数学的理论与方法,以管网节点水压和流量为评判指标,建立了震后给水管网系统服务性能的二级模糊综合评判模型.根据水压和流量的服务性能等级划分构造了单因素指标的梯形隶属函数,通过加权平均型评判模型和最大隶属度原则对管网进行综合评定,实现了地震对给水管网服务性能影响的量化评价.对一给水管网的综合评价分析结果表明,该方法可较为全面、客观地评价震后管网服务性能的优劣水平,具有一定的实用价值.

基于立压套压的气侵速度及气侵高度判断方法

为防止钻井井喷失控,针对钻井气侵情况,从井涌及压井过程中井筒溢流特性出发,建立了气液两相流气侵计算模型,给出了不同时期的初边值条件,采用有限差分法求解。模拟结果表明,钻进期间立管压力与气侵速度和气侵高度呈一一对应关系,常规压井期间套管压力与气侵速度和气侵高度呈一一对应关系。基于以上原理提出了钻进期间立管压力法和压井期间套管压力法,利用相关系数判断钻进及压井期间不同时刻的气侵速度及气侵高度。并开发了计算机自动判断气侵速度及运移高度系统,为气侵参数的判断提供了理论依据。

城市供水管网地震时的水力分析研究

震后,供水管网处于低压供水状态,使得管网中部分用户的水压和水量不能得到全部满足,导致管网部分节点的实际配水量小于需水量,为此,在传统的管网水力分析基础上考虑节点流量随水压的动态变化,进而求解管网节点实际流量和水压。为了比较传统的水力分析和考虑不同节点流量与节点压力的关系对水力分析结果的影响差异,对一实际管网进行了震后水力分析。结果表明,考虑节点流量随水压动态变化的水力分析能得到合理的节点压力和节点流量计算值。

研究液化的三维动力非线性有限元法

提出结点等价体积和三维结点等价流量的概念，综合研究了孔隙水压力在地震过程中发展和消散，考虑了正应力、剪应力及循环次数等因素对其的影响．推导出液化问题的三维动力非线性有限元理论公式．实例分析说明理论推导正确，运算简捷，对工程有实用价值．

水平管内空气-水两相流流型的混沌特征

在内径26 mm、长2 000 mm的水平管内,用差压变送器测量气液两相流不同流型下的压差波动信号,通过小波变换对信号进行除噪后,运用确定性混沌分析技术对信号进行分析,研究两相流系统分层流、泡状流、间歇流和环状流压差波动信号的混沌动力学行为.结果表明,气液两相流动系统为混沌动力系统,吸引子可用来表征气液两相流系统的动力学行为,混沌特征参数关联维D2和K熵可用来定量识别以上4种流型.

哈法亚油田自喷井停喷时间预测方法研究

哈法亚油田在开发早期依靠边底水能量自喷开采,后期需要转人工举升稳产上产,如何准确预测油井停喷时间,从而为转人工举升时机选择提供依据是一个亟待解决的重要问题.哈法亚油田具有生产气油比高和见水井含水上升较快的生产特征,常规停喷时间预测方法未考虑含水和井筒流态变化对停喷时间的影响,因此预测结果与实际偏差较大.针对该问题,提出了一套基于多相管流和节点分析技术、同时考虑含水率和地层压力变化的自喷井停喷时间预测新方法.首先采用多相管流和节点分析技术预测油井的停喷临界条件,然后利用油藏工程方法分别建立含水率及地层压力与时间的关系,最后将停喷条件与动态指标变化结合确定油井停喷时间.通过在哈法亚油田两年的实际应用,停喷预测结果与油井实际停喷时间吻合度高,验证了该方法的可靠性,同时为高气油比、见水油藏自喷井停喷时间的预测提供技术借鉴.

玛河气田高压气藏完井工艺技术

准噶尔盆地玛河气田的产层属中等孔隙度、中高渗透率储层,气藏单井产量高、压力系数高,中国石油新疆油田公司对于该类气藏的开采技术研究还处于试验摸索阶段。为此,根据该气田高压气藏的特点,应用节点分析方法对气井的流入动态曲线(IPR)、节点、敏感参数等进行计算和分析,结合冲蚀流量、卸载流量等计算方法来确定合理生产管柱尺寸及管柱结构。研究成果认为:①单井配产小于等于50×104 m3/d时,生产管柱采用内径62mm油管;②单井配产介于50×104～110×104 m3/d时,生产管柱采用内径76mm+内径62mm复合油管;③高压气井完井管柱结构为油管挂+油管+井下安全阀+油管+井下测压系统+反循环压井阀+密封插管+永久式封隔器+磨铣延伸筒+剪切球座+射孔枪串。

带鼓包的背负式大S弯进气道流场特性及参数影响规律

背负式进气口结合大S弯内管道的进气系统设计方案,由于其良好的隐身特性,在各类作战飞机上得到了广泛应用。利用自主开发的大规模并行流场解算器,对某带鼓包的背负式大S弯进气道流场特性及参数影响规律进行了一体化数值模拟研究。首先介绍了采用的数值模拟方法,通过大S弯进气道模型,验证了程序对进气道内分离流动预测的可靠性;在此基础上,对带鼓包背负式大S弯进气道在超声速来流情况下入口激波分布、进气道内部流动情况以及出口流场的气流品质进行了分析,对比分析了不同鼓包高度和唇缘后掠角对进气道性能的影响,结果显示:进气道内独特的S弯设计,会导致流动分离和二次流,造成总压损失;不同外部几何参数对进气道性能影响很大,在一定范围内,适当降低鼓包高度或减小唇缘后掠角,有利于进气道性能改善。

城市供水管网系统工况分析的研究

通过分析实际供水管网系统的特征，对管网工况分析所涉及的几个尚未解决的计算问题进行了研究，提出了用计算机进行工况分析的思路与框架，为管网运行调度及研究管网水质模型打下了良好基础．

基于压力驱动的管网漏损模型

提出了一个基于压力驱动建立管网漏损模型的方法,首先利用EPANET中EMITTER(扩散器)特性建立压力驱动水力模型,然后在模拟结果上建立管网漏损模型。通过具体算例阐述了建立符合实际的管网漏损模型的过程。结果表明,对于部分节点需水量不能全部满足的管网,压力驱动分析方法比需水量驱动分析方法得到的水力模型更符合实际,并且在压力驱动水力模型基础上建立的管网漏损模型更准确。

给水管网状态估计方法的研究

本文提出一种给水管网状态估计方法，并用试验作了验证．该方法以节点压力为主导变量进行计算，克服了节点流量难以跟踪实测的缺陷，可解决工程上一大难题．

单相热工流体网络计算软件的开发

本文基于节点压力法,建立了核动力系统流体网络数学模型,开发了适用于可压缩流体(以水或蒸汽为工质)的单相热工流体网络计算软件。仿真结果表明,该软件可应用于复杂管网系统的模拟,具有良好的稳定性。