集中式空调水系统减阻流体性能研究

结合实验对阳离子表面活性剂（CTAC）减阻流体在流道中减阻性能作了测量，分析了温度、浓度、配比变化对流体减阻性能的影响。同时应用激光相位多普勒测速仪测量了流体的速度场。研究发现，加入减阻剂后流体的减阻率可达67％，具有明显的节能效果。     

供热水系统CTAC减阻流体减阻与传热性能研究

对不同工况下不同浓度和配比的CTAC减阻流体在二维流道中的减阻性能和传热性能进行了试验测试。结果表明,在减阻流体流动达到临界雷诺数之前,传热性能下降率随雷诺数的增大逐渐增大,在达到临界雷诺数之后,传热性能急剧增强;传热性能下降率与减阻率变化趋势相同;减阻流体的温度梯度在过渡层比水大,在湍流核心区比水小。     

管道节能减阻涂料技术展望

节能减阻涂料在长距离流体输送领域有巨大的经济和社会效益，本文对节能减阻效果如何评价、流速对减阻效果的影响等，进行了分析，并对石油天然气领域减阻涂料的发展进行了展望。在水利工程中，特别是在南水北调、导流隧洞等情况下，减阻涂料非常值得推广应用。     

两性表面活性剂的湍流减阻性能与流场分析

为了研究两性表面活性剂的减阻效果和减阻机理,利用循环管路系统的方形管道对十二烷基二甲基氧化氨(OA-12)减阻流体进行了阻力测定试验,并利用粒子成像测速仪(particle imaging velocimeter,PIV)对该减阻流体的湍流流场进行了测量。阻力试验结果表明:OA-12是一种良好的减阻剂,在低雷诺数时就能取得很好的减阻效果,其减阻率会随着雷诺数的增加而增加,并达到最大值,而后随雷诺数的增加减阻率迅速下降并趋于稳定。流场分析结果表明:OA-12减阻流体之所以具有减阻效果,是因为它的存在改变了流场内部的涡量、湍流强度、雷诺切应力和平均流速等。     

弯管内减阻流体参数沿程变化模拟分析

为了研究减阻流体流动参数在弯管内的变化,利用Fluent软件对90°弯管内不同雷诺数下的黏弹性流体和水进行数值模拟。通过网格无关性验证及流动规律变化情况验证了几何模型和FENE-P黏弹性模型的可靠性。结果表明:黏弹性流体取得了一定的减阻效果,减阻率在弯道部分降低且沿程波动;流体减阻率随雷诺数的变化而变化,在临界雷诺数处减阻率最大;2种流体的壁面压力系数沿程减小,弯道部分的压力系数外侧明显高于内侧,其静水压强由外而内逐渐递减;弯道改变了轴向流速分布,外侧减阻流体流速远小于水,内侧则相反。     

空调冷水系统添加剂减阻实验研究进展

冷水系统流体输送能耗在空调系统能耗中所占比例很高,合理利用添加剂可以大幅度减小流动阻力,达到节能降耗的目的。鉴于低温情况下添加剂减阻实验研究较缺乏,设计了5~15℃添加剂减阻低温实验台,进行低温条件下减阻添加剂的筛选和减阻效果的研究。通过对十六烷基三甲基氯化铵(CTAC)及其与二十二烷基三甲基硫酸甲酯铵(BTMS)混合减阻剂的减阻效果进行实验研究,发现混合减阻剂在5~15℃温度范围内的减阻效果显著增加,特别是在管径为15.66mm、流体温度为15℃、添加剂质量分数为400×10-6时减阻百分比最大,可以达到68%。     

壁面微沟槽减阻技术研究进展

从减阻效果影响因素、减阻机理、协同减阻、实际应用等方面对壁面微沟槽减阻技术的研究进展进行归纳总结,对壁面微沟槽减阻研究方向进行展望。减阻效果影响因素包括沟槽结构、流场压力梯度等。介绍目前主流的减阻机理,关于减阻机理的各类假说仍存在争议。协同减阻的研究重点为超疏水壁面与微沟槽协同减阻、添加剂与微沟槽协同减阻。微沟槽减阻技术的实际应用涉及竞技泳衣、交通运输、流体输送等方面。研究方向为微沟槽减阻机理、微沟槽加工制造工艺、微沟槽对各类流场的适用性、微沟槽表面清洁技术。     

一种变径减阻的方法

为了降低流体通过变径时的局部阻力,让边界形状与流线最大限度的重合,避免流动过程产生的旋涡消耗能量,从而达到减阻的目的。为了找到流体通过变径时的流线的运动方程,对此提出了一种变径减阻的方法。     

膨润土种类及黄原胶含量对减阻泥浆性能的影响

减阻触变泥浆在地下综合管廊顶管施工中具有支撑、填充、润滑等重要作用。本文对减阻触变泥浆中主要原材料—膨润土的种类及含量对泥浆性能的影响进行了实验研究。结果表明：减阻泥浆的漏斗粘度、失水量和析水率等性能指标随钠基、有机和钙基3种膨润土含量的变化规律基本相同。由钠基或有机膨润土配制的泥浆失水量性能优于钙基膨润土,但钙基膨润土在泥浆漏斗粘度性能上表现更好;由上述3种类型膨润土分别配制的泥浆析水率性能相当。另外,本文还研究了黄原胶含量对减阻泥浆性能的影响,实验结果表明添加黄原胶能显著降低减阻触变泥浆的失水量,并在一定程度上提高泥浆的漏斗粘度。     

内减阻防腐涂料的制备及性能研究

文章根据基体树脂设计思路,通过主要原材料及仪器、涂料配方等制备了内减阻防腐涂料,并对其性能进行了研究,即氟碳树脂具有优异的疏水性能,酚醛环氧树脂防腐性能优异,同时固化剂能明显降低涂层减阻率,润滑填料可以明显降低涂层表面粗糙度.     

Numerical simulations of wind drags on straight and twisted polygonal buildings

This paper presents a systematic study of wind drags on high‐rise buildings of various shapes using computational fluid dynamics. By increasing the side number of a polygon, the drag coefficient of the extruded tower decreases and eventually converges to that of a circular tower. The results also show consistent reduction of wind drag when round corners are applied to the polygonal cross section and when the radius of the round corner is gradually increased. This paper also investigates the effect of twisting the building on reducing the wind drag. Design of Experiments shows that the wind drag can be reduced if the building is twisted appropriately. Copyright © 2010 John Wiley & Sons, Ltd.     

Computational Fluid Dynamics study on the performance and mechanism of suction control over a high‐rise building

In order to reduce the wind‐induced drag and improve the wind‐resistance performance of a high‐rise building, active suction control was proposed to investigate its drag‐reducing property through Computational Fluid Dynamics (CFD) method. The numerical method was validated by the experiment of suction control over a backward‐facing step flow. Effects of the dimensionless suction flux, the suction angle and the slot size on drag reduction for a high‐rise building model were analysed, and the detailed flow fields (including the time‐averaged stream and vorticity fields), the boundary layer development and turbulence characteristics like turbulent kinetic energy for the suction models were presented to discuss the mechanism of suction control. The results indicate that suction is very effective in reducing the wind‐load of a high‐rise building model, and only the dimensionless suction flux is important, while the orifice geometrical parameters and the suction velocities show little influence on drag reduction. The mechanism of suction control is concluded that suction can bring more flows around the windward face, restrain the flow separation and decrease the width of the wake for the suction models. Copyright © 2010 John Wiley & Sons, Ltd.     

减阻剂在闭式循环水系统中应用的实验研究

在闭式循环水系统中添加减阻剂能有效减小循环冷却水泵的能耗,但现有研究关于减阻剂对换热的影响认识不足.分析了减阻剂CCTDRA在闭式循环水系统中应用时浓度、雷诺数及进口水温对其减阻率和换热减少率的影响.研究结果表明:在Re=11817、体积分数为0.30％时能取得较大的减阻率及相对较小的换热减少率,在25～55℃进口水温...     

Using computational fluid dynamics to improve the drag coefficient estimates for tall buildings under wind loading

Wind is the main horizontal force acting on tall buildings. This force is proportional to the drag coefficient. The drag coefficient is an important factor in their structural design. Designers have historically relied upon experimental wind tunnel results to estimate the drag coefficient. However, this process is both expensive and time consuming. In this study, we alternatively computed the drag coefficient (apart from the pressure, force, and bending moment) using computational fluid dynamics for a typical 93‐m‐high residential building. The simulation considers the actual building geometry, as well as the neighborhood roughness effects. We compared these results with the conventional estimates contained in the Brazilian code NBR‐6123/1988 and Eurocode EC1. The results indicated that the pressures obtained herein near the top of the building were lower compared to those obtained using conventional estimation methods given in codes. Comparatively, the obtained bending moment relative to the base of the building was higher, indicating the existence of significant drag forces not considered in codes. In fluid dynamics simulations, the drag coefficient is determined for each terrain condition. Computational fluid dynamics can effectively simulate the drag force and resultant forces in the direction of the flow, as well as the vortices that result during coating detachment and other types of damage.     

Fire resistant hydraulic fluids

In an attempt to select an appropriate fire-resistant hydraulic fluid for use in Naval applications, two approaches were used: (1) development of a shear-resistant, drag-reducing colloid dispersion to determine if it had anti-misting properties, and (2) use of a water-in-oil emulsion loaded to high levels of water. While the dispersion of lithium phenylstearate colloid had demonstrated high drag reducing activity in previous work and would therefore presumably exhibit anti-misting characteristics, it failed to produce the desired fire-suppressive effect. The water-in-oil emulsion, on the other hand, showed promising fire-resistant properties in a flammability testing device.     

考虑裂隙水流拖曳力效应的平推式滑坡稳定性

为研究滑面裂隙水流拖曳力对平推式滑坡稳定性的影响,建立平推式滑坡渗流–径流耦合模型。该模型采用Navier–Stokes方程描述滑面裂隙径流,用Brinkman-extended Darcy方程描述软弱层多孔介质渗流。径流区和渗流区的流体运动均满足连续性方程,且在交界面处的流体满足流速相等和切应力连续双边界条件。根据上述条件推求出径流区和渗流区的流速分布,并引入Newton内摩擦定律求出滑动面裂隙径流拖曳力。利用刚体极限平衡理论对径流状态下平推式斜坡的稳定性进行分析,得出修正后的平推式斜坡抗滑稳定安全系数和后缘裂隙临界水深之间的关系。并结合工程实例讨论后缘水深、滑面倾角和滑面裂隙宽度对安全系数的影响。结果表明,考虑底部裂隙流体拖曳力效应时,滑坡安全系数下降了5.90%。因此,在进行平推式滑坡稳定性分析与计算中,应考虑滑动面裂隙水流拖曳力作用。     

新型高效低阻外翅管的研究

通过对外翅管绕流阻力及绕流谱的分析,提出利用翅片的外伸作用对基管进行近体扰流增效减阻的方法。单管的实验研究证实,选用合理的绊条扰流结构,可使环翅管的绕流阻力降低４０％,换热增强１０％。     

空调水系统减阻节能的实验研究

本文通过实验研究证明,在液体中加入少量的表面活性剂可导致其流动阻力大幅度地减少,即添加剂减阻现象,这样可以使得流体在输送过程中的摩阻系数显著下降,从而可以降低空调水系统的能耗。     

The drag coefficient of finite-aspect-ratio perforated circular cylinders

Measurements are described of the drag coefficient of porous circular cylinders (60% open-area ratio) fixed between solid hemispherical end caps, for five values of aspect ratio between 7.92 and 2.67. The Reynolds number varies between 10⁴ and 2.6 × 10⁵. It is found that the drag coefficient increases with aspect ratio much as a solid cylinder's but its drag coefficient is about 20% higher (varying between 0.88 to 0.96 as the aspect ratio is increased).Flow-visualization experiments have also been conducted, and show how fluid passes through the cylinders and how the vortex shedding is weaker than for solid cylinders.     

单效太阳能吸收式制冷系统发生器特性研究

数值模拟了流体在不同圆锥角度和不同入口尺寸的新型涡旋发生器中的压力分布和传热特性。结果表明,新型涡旋发生器可以有效降低吸收式制冷系统发生器内的蒸发压力和流体的发生温度,从而可以充分利用太阳能等低品位热源、提高系统的性能系数。