Effect of perforation on flow past a conic cylinder at Re=100:vortex-shedding pattern and force history

The flow past a circular-section cylinder with a conic shroud perforated with four holes at the peak was simulated numerically at Re = 100, considering two factors, viz.the angle of attack and the diameter of the holes. The effects of the perforated conic shroud on the vortex shedding pattern in the near wake was mainly investigated, as well as the time history of the drag and lift forces. In the investigated parameter space, three flow regimes were generally identified, corresponding to weak, moderate, and strong disturbance effects.In regime I, the wake can mainly be described by alternately shedding Kármán or Kármán-like vortices. In regime II, the spanwise vortices are obviously disturbed along the span due to the appearance of additional vorticity components and their interactions with the spanwise vortices, but still shed in synchronization along the spanwise direction. In regime III,the typical Kármán vortices partially or totally disappear,and some new vortex shedding patterns appear, such as-type, obliquely shedding, and crossed spanwise vortices with opposite sign. Corresponding to these complex vortex shedding patterns in the near wake, the fluid forces no longer oscillate regularly at a single vortex shedding frequency, but rather with a lower modulation frequency and multiple amplitudes. An overview of these flow regimes is presented.

Branch Quality Control of Gas-Liquid Two-Phase Flow Using a Novel T-Junction Type Distributor

In order to eliminate mal-distribution and ensure the side arm to produce desirable gas quality a special distributor is proposed. The experimental distributor mainly consists of a straight through section,a gas extraction line,a liquid extraction line and a side arm branch. A gas orifice and a liquid orifice are mounted at the gas and liquid extraction line respectively to control the outlet gas quality. The diameter of the liquid orifice was set to 2. 50 mm and three gas orifices with different size( dG= 2. 65,5. 00,10. 00 mm) were tested. The experiments were carried out at an air-water two-phase flow loop. The gas superficial velocity ranged from 6. 0 to 20. 0 m /s and the liquid superficial velocity was in the range of 0. 02- 0. 18 m /s. Flow patterns such as wave flow,slug flow and annular flow were observed. The gas quality of the side arm branch was found mainly determined by the flow area ratio of the gas orifice to the liquid orifice and independent of gas and liquid superficial velocity,flow patterns and extraction flux.

稀密两相状态监测实验平台设计

为了实际测量稀密两相对应的管道尺寸、风压和空气体积流量,设计了一个稀密两相状态监测实验平台。基于空气动力学理论和比例-积分-微分(PID)控制方法,将旁路调节系统应用到实验平台入口处,以控制管道入口空气体积流量,从而实现对物料稀密两相输送的实时监测与调控。该实验平台可实现稀密两相边界条件测试和流形稳定性分析等多项测试。最后,通过多次物料流形实验,验证了旁路调节系统在调控空气体积流量方面的有效性,以及气动测控系统维持物料流形的可行性。

Bulk Flow方法分析孔型密封转子动力特性的有效性

基于Kleynhans和Childs的两控制容积等温BF(Bulk Flow)模型,通过增加能量方程和理想气体状态方程,建立了理想气体BF方法的数学模型,来预测和分析孔型密封转子在偏心状态下的静力学和动力学特性.由于转子在密封中心附近做微小涡动,故可通过采用摄动方法使得NS方程的求解过程得到较大的简化,再通过迭代求解简化后的零阶和一阶摄动方程组,就可以求出孔型密封的流场和动力特性系数.以此为依据发展了相关程序,计算出了不同工况条件下孔型密封的转子动力特性系数与激振频率的关系,通过与已有的实验数据和等温BF模型的计算结果进行对比,验证了理想气体BF模型及相关求解方法的有效性.结果表明:理想气体BF模型的预测结果与实验数据吻合良好,且优于等温BF模型的计算结果,证明了该理想气体BF模型的正确性和计算方法的可靠性.该方法可用于孔型密封动力特性的预测.

Numerical simulation and disaster prevention for catastrophic fire airflow of main air-intake belt roadway in coal mine—A case study

Coal mine belt fire develops very rapidly and is difficult to control. If not suppressed quickly, a belt fire could easily lead to airflow disorder and undermine the ventilation system. However, belt fire can be prevented effectively by establishing fire airflow control system. In this work, the 5th belt roadway of Kongzhuang coal mine was taken as the object of investigation, where geometrical models of this roadway were established firstly. Then, based on mathematical model of fire smoke flow, the CO volume fraction, smoke density distribution, air temperature and pollutant velocity vector in the roadway before and after taking airflow control measures were simulated by using Fluent software. It can be known from the simulation that with the normal ventilation status in 5th belt roadway, the countercurrent of smoke does not happen when a fire occurs; the roadway's section is almost filled with CO at 10 m downstream from the fire source, and with air velocity getting stable gradually, the CO concentration reaches about 15 %. After taking airflow control measures, the effect range of temperature field which are harmful to the miners decreases from 69 m to 30 m; and the distance of the roadway fully filled with CO is 5 m farther than that before taking measures. Finally, according to the numerical simulation results and the actual condition of the belt roadway, the warning and automatic remote airflow control system with short-circuit method for the 5th belt roadway was designed to guarantee the safety production.

Classification of Oil-Gas-Water Three-Phase Flow in a Pipeline Based on BP Neural Network Analysis

The flow pattern in a pipeline is a very important topic in petroleum exploitation. This paper is to classify the flow pattern of oil-gas-water flow in a pipeline by using BP neural network. The effects of different parameter combinations are investigated to find the most important ones. It is shown that BP neural network can be used in the analysis of the flow pattern of three-phase flow in pipelines. In most cases, the mean square error is large for the horizontal pipes. The optimized neuron number of the middle layer changes with conditions. So, we must changes the neuron number of the middle layer in simulation for any conditions to seek the best results. These conclusions can be taken as references for further study of the flow pattern of oil-gas-water in a pipeline.

基于时空协同优化的多目标城市轨道交通延误恢复研究

针对城市轨道交通延误引起滞留旅客较多和短期运力不足的情况,提出同时采用车站限流措施和灵活跳停策略的列车延误调整方法。通过构建多目标线性规划模型,对延误列车运行图进行优化调整,将优化目标分为延误旅客总人数最小化和线路延误总时间最小化2部分,同时引入跳停决策变量,考虑跳停对计算线路总延误时间的影响,精确调整线路延误列车运行时间。多目标线性规划模型既有效缓解因滞留旅客过多造成的站台拥挤,又快速恢复因某趟列车延误造成的大面积晚点。最后通过实际算例对模型进行验证,计算结果表明该模型相较于传统的运行时刻调整策略可有效缓解站台滞留旅客的拥挤情况,缩短线路总延误时间,快速恢复城市轨道交通系统的正常运营。

基于多目标的杭州之江新城骨干河道交汇处岸线优化方案

为降低桥墩群对杭州之江新城骨干河道团结浦、三号浦交汇处的水流影响,构建了平原河网平面二维数学模型,研究了3个岸线优化方案对交汇处流态和雍水的改善效果,并综合阻水比、征地面积、水域面积及桥墩安全等多目标进行比较分析。结果表明,拓宽一侧河道以免桥墩位于主河槽或改道避开桥墩,均可有效降低桥墩雍水影响,3个优化方案对雍水高度的改善效果相当;方案2、3会影响桥墩安全,水域面积相对较小且征地面积大,方案1对桥墩安全影响较小,工程实施相对容易,综合优势较高,推荐方案1为最优方案。

基于Fluent的刚性非淹没植被排列方式对地表水流影响分析

为研究刚性非淹没植被排列方式对地表水流的影响,结合实际建立水力学模型,以植被间距均匀排列为对照组,植被条带式排列且条带间距以1.333、1.667、2.000、2.333、2.667倍数增大、条带内距离以0.833、0.667、0.500、0.333、0.167倍数减小为试验组,基于Fluent数值模拟5%植被盖度(210株)植被排列方式变化对水流流态和水力特性的影响。结果表明,植被相同盖度,排列趋于均匀:水深影响下,流速减小,水深下半段雷诺应力增大;非淹没植被上表面流速减小,紊流动能增大。消耗了水体能量达到阻水作用并减少了水流表面的冲刷。该研究为防洪减灾提供了参考。

有压+无压泄水形式在福溪水库防洪能力提升中的应用

为充分发挥水库的防洪作用,浙江省乐清市开展了水库防洪能力提升专题研究。经过论证,福溪水库可通过增设泄放洞作为水库的预泄设施,从而提升水库安全度和防洪能力。泄放洞由新旧洞子结合而成,首部新开龙抬头,后部利用原导流洞,断面、底坡变化较多,水流能否平顺衔接是一个关键问题。新建泄放洞采用进口有压短洞+无压洞的形式泄水,经计算,洞内水流可平顺衔接,洞内流态满足要求。新建泄放洞在充分利用原导流洞的基础上,提升水库预泄能力,研究成果可为类似工程提供参考。

MIKE21 FM模型在河道防洪评价中的应用

浙江浦阳江中游的诸暨段,是浦阳江历史上防洪压力最大河段,洪水危害也最严重,且诸暨段是东西江汇合处、诸暨出境的唯一水道咽喉。由于此地位置较为特殊、敏感,故在此地进行工程建设时,对如何确保此处行洪安全的研究是十分必要的。运用MIKE21 FM模型对诸暨段新建码头工程的两个方案进行对比分析为例,探讨工程实施后对河道防洪的影响,洪水数值模拟在防洪应用中具有一定价值,在河道防洪评价、防汛救灾工作中可参考其成果。

气液两相流临界分配特性及相分离控制

为实现对气液两相流的均匀分配,提出了一种由旋流叶片、整流器以及两个分流喷嘴组成的新型分配装置。其工作原理是：通过旋流叶片将来流调整为均匀环状流型,以保证两分流喷嘴入口接触气液两相流的几率相等;通过喷嘴加速两相流达到当地声速,形成临界流动,以克服喷嘴下游各支管路阻力特性不一致所导致的相分离。在气液两相流实验环道上开展了实验测试,实验分配器分流喷嘴喉部直径为8mm,扩张角为21°。实验气相折算速度范围为7-20m/s,液相折算速度范围为0.013-0.16m/s,出现的流型包括波浪流、段塞流以及半环状流。结果表明：在喷嘴喉部气液混合物速度达到声速的条件下,气液相分流系数接近理论值0.5,不受上游流型以及气液流速的影响。侧支管干度与主管干度最大偏差小于±5%,而当液相折算速度小于0.02m/s时,无法形成均匀环状流,气相更容易进入侧支管。提高液相折算速度以及喷嘴差压在分配总压降中所占比重,将有助于降低相分离程度。所提出的分配器结构紧凑,无分离装置和控制元件,基本无需维护,有望在高压两相流分配系统中获得广泛应用。

新疆地热资源成因类型及控热模式分析

新疆地热成因类型主要有断裂构造型、沉积盆地型及煤层自燃型3种。采用归类统计分析方法,结合全疆典型地热区(带、点)地热资源分布规律及赋存规律等,将区域地质构造、次级构造、大地热流背景及热源、地热水源流体等确定为地热系统形成机制的主控因素,总结出5类地热系统控热模式,为指导地热资源勘探工作具一定借鉴作用。

气液两相流波动系数及其在流型识别中的应用

为了克服已有流型识别方法受主观影响大、在线识别困难和流型识别不准确等缺点，利用对气液两相流流型影响小、压力损失小的文丘里管测量差压信号．通过计算差压信号瞬时值平均方根与平均差压方根之间的比值得到气液两相流的波动系数，提出了双参数识别气液两相流流型的方法．波动系数表明了瞬时差压偏离平均差压的程度以及截面含气率的波动程度．两相流动越不稳定，截面含气率波动越大；气液两相流各截面状态的差异越大，波动系数越大．两相流波动系数表示两相流动的波动程度，使用波动系数可以直接将分层流与其他两相流流型区别开。试验结果表明，双参数识别气液两相流流型的方法受主观影响较小，可以有效识别泡状流、塞状流、弹状流、环状流和分层流．

智能井技术在五点法井网中的应用

随着水平井技术的发展与成熟,以单水平井为主的开发模式已转化为以水平井井组整体开发为主。利用数值模拟方法研究了水平井与直井五点法井网微单元的流线特征与水平井流入量分布特征对开发效果的影响,探讨了智能井技术在水平井井网中的应用。结果表明,五点法井网微单元的流线特征决定了水平井流入量的分布特征,流入量分布越不均衡,注水开发效果越差,而通过采用智能井技术可以实时调控水平井的流入量分布,从而有效减缓注入水的突进速度,增加波及系数,提高油田的开发效益。

基于旁路的网络流量监控模式

研究了传统网络流量监控的方法和手段。针对其串联实施监控的不足,提出一种基于旁路的网络流量监控模式。通过自学习方式对应用层流量进行监测,动态形成特征库,区分网络正常流量和异常流量,进而实现对网络流量的有效控制。通过实验验证了旁路模式下网络流量监控的效率。

利用符号时间序列分析法表征垂直上升管中油水两相流流型

The flow patterns of oil/water two-phase flow in vertical upward pipes were characterized by the analysis of symbolic time series based on the conductance fluctuating signals.The study showed that the symbolic sequence temporal irreversibility T fb and chi-square χ2 fb statistics had little change with oil-in-water flow pattern variations for water cut (K w) ranging from 61% to 91% but showed irregular sudden changes with transitional flow pattern variations for water cut 51%.When distinguishing the transitional flow pattern from oil-in-water flow pattern, the symbolic time series analysis method presented more unique characteristics and was a useful assistant diagnostic tool for the identification of oil/water two- phase flow patterns.

调节阀内流型分布及利用声音突变判别流型转变的方法

针对流体诱发调节阀振动和噪声而影响汽轮机安全、稳定运行的问题,结合实验和数值模拟研究了阀内流型分布及流型与噪声、振动的关系。研究表明:在中小升程下调节阀内存在2种流型,其中附阀座流相对于冲击射流是一种更加稳定且噪声较小的流型;不同压比调节方式下,即使同一工况也会出现这2种流型;连续改变压比会出现一种声音突变现象,该现象由附阀座流和冲击射流的转变所致;利用声音突变可以确定调节阀在中小升程下流型区域的分布范围,可为判断数值模拟所得流型的正确性提供参考。

十二流中间包的物理模拟

国内首家建设的12机12流连铸机的中间包属于特殊不对称型中间包,包内各流之间的流动特征存在着明显的差异,造成操作困难。采用1∶3缩小比例的水模型和"刺激-响应"方法,对其内流场进行研究,并开发了D型控流装置。该装置在模型中能有效地将各流之间的最大平均停留时间差从546 s降到50 s,死区从26.8%下降到12.9%,还能有效地降低中间包的不对称度和提高钢液在中间包内的平均停留时间。这对均衡各流的操作参数,提高铸坯质量起到重要作用。

西澳大陆架深水重力流砂体富集规律及主控因素

澳大利亚西北大陆架是目前全球深水油气勘探的热点区域。针对西澳大陆架Vulcan次盆南部Vulcan组砂体成因类型、沉积体系展布、富砂区控因不明确等问题,通过岩芯观察、钻测井资料和地震属性的分析,刻画了以海相三角洲前缘滑塌体为主导的贫砂富泥型深水沉积体展布,重点研究了深水沉积砂体的分布规律和富集主控因素。认为研究区东南部的缓坡带发育海相三角洲,在Swan地堑边界断层下降盘发育滑塌体和浊积体,北西部的陡坡带发育水下扇沉积。深水砂体的富集在4个层次上受5种因素的控制,表现为"四级五元"的控制特征,即:构造决定了沉积体系类型,海平面的升降约束了砂体在层序中的分布层位,沉积底形控制了深水沉积体系的外观形态,断层调节带改变了沉积体系的分布格局,深水底流对砂体进行了二次分配。该认识对研究区寻找规模储层和油气勘探都有重要作用。