基于HEC-RAS的平陆运河河口段流速模拟及疏浚施工影响分析

针对河口段水流形态复杂多变,不利于组织河道疏浚施工的问题,以西部陆海新通道(平陆运河)为例,应用HEC-RAS一维非恒定流水力学计算模块,构建运河河口段水动力模型,并对模型糙率进行率定及模型精度进行验证。在此基础上,根据青年水闸(闸下)水位及流量特征,设定闸下4种流量(水位)工况,模拟分析河道流速的变化。结果表明:HEC-RAS模型在感潮河段模拟精度较高,具有较好的适用性;随断面流量的增加,石江墩河段S26一S32流速响应迅速,流速大值平均值较其他河段高约34.0%。研究成果可为运河河口段航道疏浚工程施工提供技术支撑。

套管旋流扶正器的流速模拟研究和应用

采用贝塞尔函数解形式模拟了经过套管旋流扶正器的泥浆和水泥浆的旋流衰减速度场,并进行了以泥浆为介质的全尺寸环空旋流衰减速度场超声波测试,分析了套管旋流扶正器后的速度场衰减机理,数值模拟结果与实际测试曲线趋于一致。在此基础上进行了旋流注水泥工程设计计算和应用。

先导式泄压阀泄放过程流速模拟分析

结合某成品油管道,介绍了先导式泄压阀的选型,采用Fluent软件对先导式泄压阀泄放过程流速进行模拟分析。结果表明:先导式泄压阀阀芯部分会有明显的节流效应,随着泄放压力的变化和管线沿程摩阻损失,泄压阀出口管道速度总体呈现先增大后减小的趋势,流速在进泄压罐前已降至安全值,不会因流速过高而对泄压罐造成影响。

一种流体流速模拟平台的系统设计

海流是海洋水文的三大要素之一,海流流速的模拟和测量是研究海洋的基础,对国家的海洋战略具有重大意义。为了能够在实验环境下模拟海水的流动,文章设计了一种基于速度分解原理的海水垂直流和水平流的模拟平台。首先,介绍了平台的工作原理,对关键部件进行了强度计算与有限元仿真分析。其次,基于模糊PID控制方法设计了平台的伺服控制系统,并通过Simulink仿真比较了采用传统PID和模糊PID控制器的直线电机模型对于阶跃信号的响应。最后,对水平状态下的直线电机进行实验。有限元分析表明主支撑板的最大相对形变量为0.1196 mm,满足直线电机对主支撑板的形变要求,电机实验则表明,对采用模糊PID控制器的直线电机进行速度为10 mm/s的等速引导时稳态误差为0.17 mm/s,验证了模糊PID的有效性,稳态时电机的速度波动在2%以内,能够满足模拟海水流动的要求。

基于超声波流量计的流速模拟器设计

为了解决超声波流量计必须在管道以及流体都存在的情况下才可以进行信号链路功能测试的不便性,设计了一种专门针对超声波流量计的流速模拟系统。流速模拟系统以FPGA为核心,实现了对待测超声波流量计发射起始时间点的检测以及模拟回波信号的产生。通过分别测量顺流和逆流两种情况下的渡越时间差,计算被测流体的流速和流量,并进行数据分析,方便快捷地实现了对超声波流量计收发信号链路的功能验证。

质量流量计流速模拟系统设计与实现

质量流量计流速模拟系统用于对质量流量计的流速进行模拟,目的是在不需要实际管道流体的情况下,通过该模拟系统测试质量流量计是否正常工作。模拟系统的实现是基于FPGA的控制系统,FPGA控制高速DA转换器,输出两路频率相同、幅值相同、相位不同的正弦信号,用于模拟质量流量计两磁电传感器的时间差,实现流速的模拟和线性度分析,并由此判断质量流量计的基本测量功能是否正常。测试结果表明,在实验室环境下,模拟系统可以输出对应质量流量计满量程的相位差信号,同时可以验证在理想输入波形下质量流量计的线性度,该过程无需实流条件,用较低的成本即可验证质量流量计整机功能是否正常。

淬火槽中介质流速的测量及流速场的模拟

为了研究淬火槽中流速场的分布状态 ,提高流体均匀性 ,采用超声波多普勒流速测定仪对螺旋桨搅拌状态下的介质流速进行了测量 ,用有限元法对流速场进行了模拟 ,并根据模拟结果对均流片的设置进行了改进。结果表明 ,试验选用的超声波多普勒流速测定仪及其测量方法适合于测量工业淬火槽的介质流速 ;

考虑气相影响的塔板流速场模拟

The vapor phase passing through the flowing liquid on a distillation tray exerts a resisting force on the liquid phase and,at the same time,enhances liquid turbulence.Both of these effects should be considered in the modeling of the Liquid velocity field.A mathematical model considering both effects isdeveloped.The comparison of the computed results with experiments shows that the proposed model is more suitable for simulating the velocity field on distillation trays than existing model.

近海岸潮流发电模拟装置中造流方法研究

在海洋能发电中,潮流发电具有广阔的发展前景。为在实验室进行潮流发电的前期研究,设计了潮流发电模拟装置。由于近海岸潮流能分布较大,在模拟装置中进行近海岸的潮流流速模拟,即造流。在模拟装置的控制系统中,通过上位机控制变频器输出电源的频率和相序,从而驱动三相异步电动机带动双向叶轮泵推动水的流动。为此在上位机上设计了Lab VIEW操作界面以及程序框图,利用VISA技术进行数据发送与接收,将流速对应的频率信号发送给变频器,并将流速传感器采集到的流速信号接收到上位机进行实时显示。研究稳定流速和变化流速的造流方法,对稳定流速、椭圆余弦波流速和沿岸流流速进行造流实验,结果表明模拟流速与预设流速总体误差较小,较好地实现了实验室潮流发电的模拟。

梯形转叶螺旋流消能装置消能过程的数值模拟分析

为了从微观角度探究梯形转叶螺旋流消能装置的消能机理、验证其结构设计的合理性及不同参数对装置消能效果的影响,基于试验研究,运用Fluent软件进行三维螺旋流数值模拟。结果表明,数值模拟显示的消能机理与试验结果相吻合;装置消能的主力区在转叶孔板组合后,且装置的结构设计合理;转叶螺旋流消能装置的消能效果优于同类孔板射流装置的消能效果;在一定条件下,装置的消能效率与雷诺数和扭转角度均呈正比,而与开口角度呈反比。该结论为梯形转叶螺旋流消能装置的消能过程研究提供了依据,也为其结构优化和实际应用提供了理论支持。

改善港口口门流态相关工程措施的研究

港口口门水域的流态是港口规划建设时需重点考虑的问题,口门流速过大会影响船舶进出港的通航安全。结合某港区规划方案和青岛港某码头规划设计方案,通过流场数值模拟,分析造成口门水域流速过大的不同原因,提出改善口门水流条件的相应工程措施。

一种潮流发电实验装置控制系统设计

为在实验室环境下研究潮流能发电特性,设计了一种潮流发电模拟实验装置。通过研究实际海域的潮流流速变化规律,建立流速模型。设计潮流发电模拟装置,输出所建立的流速模型。装置主要包括潮流模拟装置、潮流控制装置、测量装置。装置可以模拟出3m/s以下不同潮流流速模型,同时流速误差控制在10%以下。实验结果表明此装置运行稳定、性能可靠、控制方便,能够作为潮流发电研究的辅助设备。

Laser Measurement and Intensity Evaluation of Intake Swirl in Engine Using a Water Analog

The intake swirl in the cylinder was induced by a swirler which was fixed in one of two intake ports. In order to understand the characteristics of the intake swirl, a transparent water analog was designed which simulated 150 type single cylinder engine. At the same time, the particle image velocimetry was used to measure the flow fields induced by various swirlers in the analog. After measurement, a new method was presented to evaluate the intensity of the intake swirl. Then, when the measured sections, the lifts of valve and the swirlers were different, the calculated results of the flow field were compared.

Phase-field simulations of forced flow effect on dendritic growth perpendicular to flow

The effect of supercooled melt forced laminar flow at low Reynolds Number on dendritic growth perpendicular to melt flow direction was investigated with the phase-field method by incorporating melt convection and thermal noise under non-isothermal condition. By taking the dendritic growth of high pure succinonitrile （SCN） supercooled melt as an example, side-branching shape difference of melts with flow and without flow was analyzed. Relationships among supercooled melt inflow velocity, deflexion angle of dendritic arm and dendritic tip growth velocity were studied. Results show that the melt inflow velocity has few effects on the dendritic tip growth velocity. A formula of relationship between the velocity of the melt in front of primary dendritic tip and the dendritic growth time was deduced, and the calculated result was in quantitative agreement with the simulation result.

CFD numerical simulation of flow velocity characteristics of hydrocyclone

A CFD based numerical simulation of flow velocity of hydrocyclone was conducted with different structural and operational parameters to investigate its distribution characteristics and influencing mechanism. The results show there exist several unsymmetrical envelopes of equal vertical velocities in both upward inner flows and downward outer flows in the hydrocyclone, and the cone angle and apex diameter have remarkable influence on the vertical location of the cone bottom of the envelope of zero vertical velocity. It is also found that the tangential velocity isolines exist in the horizontal planes located in the effective separation region of hydrocyclone. The increase of feed pressure has almost no effect on the distribution characteristics of both vertical velocity and tangential velocity in hydrocyclone, but the magnitude and gradient of tangential velocity are increased obviously to make the motion velocity of high density particles to the wall increased and to make the cyclonic separation effect improved.

NUMERICAL SIMULATION OF SUPERSONIC AXISYMMETRIC FLOW OVER MISSILE AFTERBODY WITH JET EXHAUST USING POSITIVE SCHEMES

Supersonic axisymmetric jet flow over a missile afterbody containing exhaust jet is simulated using the second order accurate positive schemes method developed for solving the axisymmetric Euler equations based on the 2-D conservation laws.Comparisons between the numerical results and the experimental measurements show excellent agreements.The computed results are in good agreement with the numerical solutions obtained by using third order accurate RKDG finite element method.The results show larger gradient at discontinuous points compared with those obtained by second order accurate TVD schemes.It indicates that the presented method is efficient and reliable for solving the axisymmetric jet with external freestream flows,and shows that the method captures shocks well without numerical noise.

Phase-field simulation of forced flow effect on random preferred growth direction of multiple grains

The random distribution problem of dendrite preferred growth direction was settled by random grid method.This method was used to study the influence of forced laminar flow effect on multiple grains during solidification.Taking high pure succinonitrile （SCN） undercooled melt as an example,the forced laminar flow effect on multiple grains was studied by phase-field model of single grain which coupled with flow equations at non-isothermal condition.The simulation results show that the random grid method can reasonably settle the problem of random distribution and is more effective.When the solid fraction is relatively low,melt particles flow around the downstream side of dendrite,and the flow velocity between two dendrite arms becomes high.At the stage of solidification time less than 1800Δt,every dendrite grows freely;the upstream dendrites are stronger than the downstream ones.The higher the melt flow rate,the higher the solid fraction.However,when the solid fraction is relatively high,the dendrite arm intertwins and only a little residual melt which is not encapsulated can flow;the solid fraction will gradually tend to equal to solid fraction of melt without flow.

壳聚糖改性黏土作用下湖泛致黑悬浮物的沉降特性研究

为了探讨湖泛致黑物质在壳聚糖改性黏土作用下的絮凝沉降以及再悬浮的规律,利用柱状水槽再悬浮发生模拟装置,选取壳聚糖改性黏土(1 g/L硅藻土+0.2 g/L壳聚糖)作为絮凝剂,进行了风浪扰动作用下太湖湖泛的絮凝及再悬浮过程的室内模拟试验。结果表明:当模拟流速产生的切应力超过0.042 N/m^2时,低浊度组中的黏土絮体产生了明显的再悬浮现象;当流速产生的切应力超过0.109 N/m^2时,高浊度组发生再悬浮。对比太湖不同风速所产生的切应力,发现4 m/s以下的太湖风情产生的湖流切应力不会使黏土絮体发生再悬浮。研究旨在为太湖湖泛的应急处置提供参考。

Mathematical modelling and numerical optimization of particle heating process in copper flash furnace

A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft,whilst the convection is dominant in the area below 0.6 m for the particle heating.In order to accelerate the particle ignition,it is necessary to enhance the convection,thus to speed up the particle heating.A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace,aiming to create a lateral disturbance in the gaseous phase around the particles,so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient.Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners.The results show that with the high-speed jet technology,particles are heated up more rapidly and ignited much earlier,especially within the area of the radial range of R=0.3−0.6 m.As a result,a more efficient smelting process can be achieved under the same operational condition.

Aerodynamic noise characteristics of high-speed train foremost bogie section

This paper investigates the main scale analysis of the aerodynamic noise in the foremost bogie area by the large-eddy simulation(LES)and the Ffowcs Williams-Hawkings(FW-H)analogy.The mechanism of the aerodynamic noise in this area has been excavated.The aerodynamic excitation results show that the bogie divides the bogie compartment into two cavities,each of which contains a large circulating flow and presents multi-peak characteristics in the frequency domain.The far-field noise results suggest that in the speed range of 200−350 km/h,the aerodynamic noise mechanism in the bogie area is the same.Cavity noise is the main noise mechanism in the foremost bogie area,and the bogie divides the bogie cabin into two cavities,thereby changing the aerodynamic noise in this area.