平行平板间填充球形颗粒的流动特性

对平行平板间填充小颗粒后的流动实验结果进行了归纳和分析，表明流动阻力远远小于微颗粒填充，同时在小的颗粒填充层数下，壁面效应对流动阻力特性有显著的影响，流动呈现出与细微颗粒堆积多孔介质不同的流动规律。在实验结果的基础上，通过定义壁面修正因子考虑壁面效应的影响，得到了颗粒堆积多孔介质在小填充层数时流动阻力特性的准则关系式。     

选择性催化还原法烟气脱硝装置流动及阻力特性的研究

利用CFD软件Fluent对300MW机组的选择性催化还原法烟气脱硝装置流动特性进行了数值模拟研究，分析了导流装置、喷氦格栅和反应器折烟角等对系统阻力特性的影响。研究结果表明，导流和整流装置可极大地改善装置内的流动特性，导流板可起到流动优化和降低阻力的作用。在喷氨格栅中，防磨板对反应器系统阻力的影响较小，合适的折烟角变动可以降低阻力损失。     

液力偶合器负荷特性的计算方法

本文根据流体力学的能量转换和粘性流动阻力理论,建立偶合器循环圆内的流动模型,导出了偶合器负荷特性的计算公式及流动阻力计算方法。运用这种方法,对流道几何参数和流动阻力损失进行分析计算,可得到偶合器的转矩随速比变化的规律,进而对有关几何参数和腔室形状修改,将可得到预期的负荷特性。     

隧道对超车过程车辆瞬态气动特性的影响

该文利用动网格和滑动交界面技术实现了一辆轿车超过一辆大型货车过程的三维瞬态数值模拟,分别模拟了在开阔路面和单向双车道隧道内两种工况下的超车过程.通过对车辆外流场进行分析,找出了隧道内超车过程中被超车和主超车的气动力变化规律,并与开阔路面上的相同过程进行了对比.结果表明:超车过程对被超车货车的气动特性影响大,其阻力系数和侧向力系数均发生大幅度变化,呈现类似正弦变化的趋势,而对主超车轿车影响相对较小;隧道内与开阔路面上两种超车过程中,两车侧向力和阻力的变化规律均相同,但是隧道内车辆气动力系数的变化幅度却大于开阔路面,显示隧道内超车对车辆行驶稳定性的影响更大,其安全性更需重视.     

有气阀的长距离输水管道流动特性分析与应用

长距离输水管道为了补(排)气需要安装气阀，气阀工作时在阀附近的管道内会形成空穴，并且以气阀为中心，上下游管系、空穴和气阀组成一个局部的小系统，形成管系水流特性、空穴参数和过阀气流特性的连续同步变化，并使管内出现振荡流动。本文通过计算实例对过阀气流参数按等熵流动过程计算，空穴参数按等温过程计算，上、下游管系内的水流特性则按非定常流动计算，其计算结果基本符合实际情况。由此得到的过阀气流的质量流量，可用于选择气阀的过流面积，而管系内水流的振荡流动特性，可供管道系统设计、气阀布设安装时参考。     

基于叶素理论及 CFD 的中扬程风力提水机的 低实度高效风轮设计

为了降低风力提水机的起动风速,解决传统风力提水机多叶片大实度、风能利用系数低的缺点,采用叶素理论对风力提水机叶片的气动外形进行设计,引入了修正因子,并根据工程实际优化了叶片的弦长以及安装角;采用CFD方法对风轮进行数值模拟,通过分析证明所设计的风力提水机能在2.5m/s的微风下起动,在额定工况下风能利用系数高达0.46,叶片具有很好的三维流动特性,气流流动稳定无脱流,具有中扬程、低实度、低风速起动进行提水作业的优点,扩大了风能的利用范围。     

排烟冷却塔的一维设计计算方法

利用冷却塔排放烟气,须在冷却塔内增加排烟管道,且在填料断面又增加了烟气流量.冷却塔工艺设计如何进行计算,是冷却塔设计遇到的一个新问题.本文在分析了排烟塔气流特性的基础上,参照类似气流阻力的研究结果结合自然塔的热力计算方法,给出了排烟冷却塔的热力阻力一维计算方法,计算与分析结果表明,计算具有一定的精度,可供设计参考.     

超大型自然通风冷却塔进风口区域阻力特性研究

随着淋水面积的逐渐增大,现行的阻力计算公式已不再适用于超大型冷却塔的计算。本文通过对应建立超大型冷却塔冷态气流阻力试验模型,对不同规模冷却塔的支撑结构（包括人字柱及塔内支撑柱）、不同淋水填料阻力、不同进风口高度等进行组合试验,对其相应阻力特性进行了分析,在此基础上提出了适用于超大型常规逆流式自然通风冷却塔进风口区域阻力系数计算公式,并经过了工程验证。     

气动冲淤数值仿真模型研究

为进一步探索气动冲淤的作用机理和在工程实践中的应用,进行了气动冲淤数值仿真模型研究。采用立面二维水-沙-气三相仿真模型,对气动冲淤中气体及泥沙运动特性进行了探索,并对比了气动冲淤与水射流冲刷的优缺点。结果表明:①采用气动冲淤时,气流冲击到泥沙后向上运动,同时带动泥沙向上运动,随之被水流带走。相同条件下,水射流的冲刷范围大,但气动冲淤的冲沙效率更高,采用气动冲淤能达到较好的清淤效果。②气动冲淤中,气体流速越大,冲刷效果越明显,冲沙率随气体弗劳德数的增大呈线性增大趋势。     

充分发展管流中环塞的局部阻力特性

准确评价流动横截面积突变管件的局部阻力对提高管路系统构筑的经济性意义重大。为揭示 圆管充分发展流中的一个局部突缩元件的阻力特性,实验测试了不同长径比和孔径比的内置环塞在充 分发展管流中的局部阻力。实验结果表明:在孔径比一定的条件下,环塞的轴向长度较小时,局部阻力 较大;而当环塞轴向长度较大时,局部阻力较小。环塞轴向长度一定时,孔径比加大,局部阻力减小;孔 径比减小,局部阻力增大。对两环塞的阻力系数不产生影响的最小塞间距,随孔径比减小而增大。通过 植入环塞内壁的绒毛随流摆动实验说明,孔径比的减小将使塞内流动的附壁长度增加。由流动分离后 缩颈程度及呈现位置变化的分离流分析,解释了环塞的上述局部阻力特性。     

CHARACTERISTICS OF WIND DEFLECTOR FOR REDUCING AERODYNAMIC DRAG OF VAN-BODY TRUCK

1 .　INTRODUCTIONVan bodytruckshavesbeeninincreasinglywideuseinrecentyearsduetomanyadvantagessuchaspreventingrain ,sunshineanddust ,loadingorunloadingconvenientlyandsafety .AlongwiththerapiddevelopmentoffreewayinChina ,theaveragespeedofautomobileshasbeen greatlyraised .Theaerodynamicshapeofthevan bodytruckisnotsogoodowingtoitslargeaerodynamicdragcausedbyitsstructure ,whichisproportionaltothespeedofthetruck ,andincreasesnotablyinthefractionofthetotaldragcomparedwiththeconventionaltrucks .E…     

AERODYNAMIC CHARACTERISTICS ABOUT MINING DUMP TRUCK AND THE IMPROVEMENT OF HEAD SHAPE

The external flow field around a certain mining dump truck was simulated. The airflow structure and the aerodynamic drag were discussed, and the relationship between airflow characteristics and aerodynamic drag were obtained. In order to solve the problem of head shape of the truck, three scenarios including edge rounding, installing splitter planes and their combination were put forward to improve the head shape through numerical simulation and analysis. The model and method were selected to be three dimensional and time-independent. The Reynolds-averaged Navier-Stokes equations were solved using the finite volume method. The RNG k-ε model was chosen for the closure of the turbulent quantities. The results show that the third scenario is the best one, because of its aerodynamic characteristics being better than those of unimproved model.     

STUDY ON AERODYNAMIC CHARACTERISTICS OF VAN-BODY TRUCKS

ＢＲＩＥＦＩＮＴＲＯＤＵＣＴＩＯＮＯＦＴＨＥＰＡＰＥＲ :　Ｔｈｅｖａｎ ｂｏｄｙｔｒｕｃｋｉｓａｂｌｕｎｔｂｏｄｙｗｉｔｈｉｒｒｅｇｕｌａｒｓｈａｐｅ .Ｔｈｉｓｐａｐｅｒｆｉｒｓｔｌｙｄｅａｌｔｗｉｔｈｍａｎｙｐｒｏｂｌｅｍｓｉｎｅｘｐｅｒｉｍｅｎｔａｌｔ     

THE RELATIONSHIP BETWEEN FLOW CHARACTERISTICSAND AERODYNAMIC DRAG OF VAN-BODY TRUCK

1.INTRODUCTIONInrecentyears,thedevelopmentoftransportationfacilitiesandtheautomobileindustryhavemadethenormalvehiclerunfaster,thustheaerodynamicdragincreasesalotandsodoesthefuelconsumptionaccordingly.Thisproblemisevidentespeciallyforvan-bodytruck-Inordertoimprovetheaeredynamiccharacteristicsandreducethefuelconsumptionforvan-bodytruck,manyeffortshavebeenmadeondrag-reducingattachments-[2-5jHowever,thereisnotenoughworkdoneonthesurfaceairflowcharacteristicsandtherela-tionshipbetweenflowcharac…     

EXPERIMENTAL AND NUMERICAL STUDIES OF AERODYNAMIC PERFORMANCE OF TRUCKS

This article studies the truck-induced airflow. The results of numerical investigations are used to assess the effectiveness of the installed hash symbol (#) shaped fence on the truck. The Reynolds-averaged Navier-Stokes equations are solved using the finite volume method. The computed distributions of the pressure and the air velocity as well as the computed aerodynamic drag coefficients reveal the effects of a fence on the aerodynamic performance of the truck. It is shown that the hash symbol shaped fence...     

Transient aerodynamic characteristics of vans during the accelerated overtaking process

This paper studies the influence of the accelerated overtaking process on the vehicles' transient aerodynamic characteristics, through 3-D numerical simulations with dynamic meshes and sliding interface technique. Numerical accuracy is verified by experimental results. The aerodynamic characteristics of vehicles in the uniform overtaking process and the accelerated overtaking process are compared. It is shown that the speed variation of the overtaking van would influence the aerodynamic characteristics of the two vans, with greater influence on the overtaken van than on the overtaking van. The simulations of three different accelerated overtaking processes show that the greater the acceleration of the overtaking van, the larger the aerodynamic coefficients of the overtaken van. When the acceleration of the overtaking van increases by 1 m/s2, the maximum drag force, side force and yawing moment coefficients of the overtaken van all increase by more than 6%, to seriously affect the power performance and the stability of the vehicles. The analysis of the pressure fields under different accelerated conditions reveals the cause of variations of the aerodynamic characteristics of vehicles.     

THE TRANSIENT AERODYNAMIC CHARACTERISTICS AROUND VANS RUNNING INTO A ROAD TUNNEL

In this article,the processes of vans running into a one-way two-lane road tunnel are simulated numerically using the dynamic mesh technique and RNG k ? ε turbulence model.The transient aerodynamic characteristics around vans are obtained in three cases:a single van,two vans side-by-side and two vans one after another running into the tunnel,respectively.Through a comparison with the results of the wind tunnel experiment,the transient simulation method is verified.The results show that,when a van runs into the tunnel,the aerodynamic drag coefficient increases near the tunnel entrance,and after entering the tunnel,the side force is generated,pointing to the tunnel wall nearer to the van.When two vans run into the tunnel side-by-side,their drag coefficients increase by 50%,and the side force varies sharply with directions changing twice near the tunnel entrance.When two vans run into tunnel one after another,the aerodynamic characteristics around the van in the front is similar to that of a single van,but the aerodynamic forces on the van behind do not have obvious change.Among the three cases,the aerodynamic forces have a sharp change when two vans run side-by-side,so driving side-by-side into a tunnel should be avoided for safety.     

斯太尔邮政车外形结构参数和气动阻力特性关系的研究

通过风洞试验研究了斯太尔邮政车外形结构参数变化时的气阻力特性；并对不同型式的导流罩的减阻效果进行了试验研究，为该车种的变形设计提供了依据。     

Numerical simulation of the aerodynamic characteristics of heavy-duty trucks through viaduct in crosswind

In our numerical simulation the hybrid mesh and the SST k-ω turbulence model are adopted to investigate the variations of the aerodynamic loads and the flow field of heavy-duty trucks while crossing a viaduct with 1.1 m high fences in a crosswind at a velocity of 20 m/s. The results show that, with the protection of a fence, the side force is weakened, and the rolling and yaw moments are strengthened while the truck is crossing the viaduct, which relatively reduces the roll-over safety and the driving stability of the truck. Meanwhile, the direction of the side force changes when the truck enters the viaduct, which makes the roll-over safety and the driving stability the lowest during the process.