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1.
Flow visualization and hot-wire measurement techniques were combined to investigate the influence of the size and number of tabs on jet flow field and vortex structure generation mechanism. Streamwise vortices generated by the tabs of different sizes and numbers were ob- served from the flow visualization images. Combined with flow visualization, hot-wire measurement gave a quantitative insight of the effect of various tabbed jet flows. Instantaneous two-component velocity signals （longitudinal and transverse velocity components） at different cross sections along radius direction and streamwise direction with different tabbed jet nozzles were measured using hot-wire anemometer. Average flow field parameters of tabbed jet flow such as mean velocity, turbulence intensity, vorticity were analyzed and the effects of tabs with different sizes and numbers were compared with that of circular no-tab jet flow. It is revealed that the generation of a series of counter-rotating quasi-streamwise vortices, azimuthal vortices and double-row azi-muthal vortex are the reasons for mixing enhancement of tabbed turbulent jet flow. 相似文献
2.
为了解不同空调风机的内流机制,采用数值分析和PIV实验研究相结合的方法对空调用贯流风机和轴流风机内部复杂的旋涡流动现象进行了研究。结果表明:空调壁挂机用贯流风机内部偏心涡沿轴向具有明显的三维分布特性,偏心涡径向位置沿轴向几乎没有变化,其周向位置沿轴向不断改变。贯流风机偏心涡卷吸区域随负载提高而增强。高负载时,偏心涡更加靠近叶轮中心和蜗壳方向。空调室外机用开式斜流风轮的叶尖涡产生于距叶片前缘1/4区域,靠近吸力面。叶尖涡随风轮转速的提高而增强,并沿着与风轮旋向相反的方向朝下游发展。 相似文献
3.
With the development of ski-jump energy dissipation for high and large discharge among the hydraulic projects, the effects of characteristics of water flow on energy dissipation are increasingly important. In the present study, the effects of aeration and the initial water thickness on axial velocity attenuation of jet flow were analyzed, using variance analysis and numerical calculated methods. From the analysis of test data, both of the air concentration and initial water thickness are sensitive factors for the axial velocity attenuation of jet flow along the axial way, and there is no significant interaction effect between the aeration and initial water thickness. Aeration has a more significant effect on the axial velocity attenuation of jet flow. Decreasing the initial water thickness of jet flow can reduce the length of jet core, and make the initial position of axial velocity attenuation closer to the nozzle exit. The numerical calculation results show that aeration can contribute to the enhancement of entrainment ability of jet flow, which may improve the interaction between jet flow and surroundings. For ski-jump energy dissipation among the hydraulic projects, combining aeration with decreasing initial water thickness of jet flow is an effective way to enhance the rate of axial velocity attenuation. 相似文献
4.
采用陶瓷微滤膜,以硫酸法生产的TiO（OH）2粉体浆料为对象,研究了洗涤过程中粉体Zeta电位变化对粉体分散性影响。实验考察了操作压差、错流速率、洗涤次数等工艺参数的影响。确立了操作压差和膜面流速分别为0.12 MPa和1.5 m/s较为合适该体系参数。随着洗涤次数增加,物料中电解质浓度不断降低,粉体颗粒表面Zeta电位绝对值升高,颗粒之间相互排斥作用增强,渗透阻力降低,渗透通量提高,粉体分散性提高。 相似文献
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通过刚性模型风洞测压试验,研究了风向沿马鞍低点连线时菱形马鞍屋盖表面的风压特性.首先给出了屋盖表面的平均及脉动风压分布,通过脉动风压谱,从微观角度阐述了迎风前缘附近旋涡从生成、发展直到最后破裂的过程,进而解释了迎风前缘易损区域的平均及脉动风压分布机理.分析马鞍高点附近的风压谱形状,发现结构对于来流的干扰作用在风压脉动上体现为高频脉动.此后用测点风压时程的三、四阶矩对风压的非高斯特性进行描述并给出了划分高斯、非高斯区的标准,在此基础上对马鞍屋盖表面进行了分区.通过研究脉动风压谱,发现风压非高斯特性是由于来流的分离运动及结构对来流的干扰作用引起的,且前者引起的非高斯特性较后者更为显著. 相似文献
6.
介绍了一种用于强化管壳式换热器壳侧传热和支撑管束的螺旋折流片新型结构,该结构是对换热器管子相间地套上螺旋折流片以产生旋涡流动.研究模型是在正方形布置的4个管子中的2个对角管子套上螺旋折流片后形成的通道,利用FLUENT软件对该上述四管通道模型的流场和温度分布情况进行了数值模拟;分析了四管通道模型中螺旋折流片对强化传热和流动阻力随雷诺数的变化关系的影响.算例结果显示该新型结构可比相同尺寸的光管通道中的情形传热系数提高约40%～55%,同时也将伴随较高的流动阻力.可以相信螺旋折流片式换热器将会在许多工业领域有良好的应用前景. 相似文献
7.
水合物法分离含氢气体混合物的实验研究 总被引：1，自引：0，他引：1
许维秀 《荆门职业技术学院学报》2006,21(6):1-4
利用高压水合物分离装置,在不同的温度、压力及液体流量下,分别测定了H2、CH4二元混合物与水合物促进剂进行水合反应时分离效果随时间的变化.结果表明,温度越低,体系压力越高,液体流量越大,H2浓度增加越快,但较高的压力对分离效果影响较小,过大的液体流量会加大液体夹带量.适宜的条件为:温度5~10℃,压力4.5~5.0 MPa,合适的液体流量应根据实际情况确定. 相似文献
8.
城市地下过街通道是城市重要的交通系统组成部分,也经常会成为恐怖分子爆炸袭击的对象。为了更好的了解爆炸冲击波在地下过街通道中的传播规律,本文通过数值模拟分析了13KG炸药在通道爆炸后冲击波的传播。分析过程中分别考虑了炸药起爆位置及通道顶盖对冲击波传播的影响。分析结果表明当TNT在通道内起爆后,通道顶部的角落将受到更大的冲击波压力作用,当冲击波从出口向外传播时将发生明显的射流现象;当通道出口有顶盖时,炸药在出口的起爆将明显加强通道内部及出口梯道的压力峰值。 相似文献
9.
1 Introduction Sealing with magnetic fluids is one of the most suc-cessful applications of magnetic fluids .This techniquewas first put forward in the 1970’s .It overcomes thedisadvantages in traditional sealing. Rotational leakage has al ways been a pro… 相似文献
10.
NomenclatureV-Relative velocity vectorV′-Absolute velocity vectorω-Relative vorticity vectorω′-Absolute vorticity vectorR-Pipe radiusa-Radius of cylinder for helical vortex filament2πl-Pitch of i mage helical vortex filamentQ-Flowrate in pipe with an arbitrary cross-sectionΓ-Circulation of each helical vortex filamentV0-Constant transferal velocity of vortex filaments along thez-axisΩ-Constant angular velocity of vortex filaments around thez-axis(a,χ1) ,(a,χ2) -Relative helical … 相似文献
11.
Characteristics of R22 and its new alternative refrigerant R290 flowing through adiabatic capillary tubes are investigated based on the homogeneous model.Extensive flow variables along tube length such as pressure, temperature, viscosity, velocity, Reynolds number, friction factor and vapor quality etc are compared between the two fluids under the same operating condition. Two cases are considered, namely, either the same tube length or the same mass flow rate as inlet condition. The results show that the mass flow rate in the capillary tube of R290 is 40% lower than that of R22 due to the differences of physical properties between the two fluids. Further, a parametric analysis is performed and it appears that effects of geometric and thermodynamic parameters on mass flow rate of R290 are weaker than that of R22. When the condensing temperature is increased from 40 ℃ to 50 ℃, the mass flow rate for R22 is increased by 16%, while the increasing rate for R290 is 13%. 相似文献
12.
Vortex-ring cavitation occurs when the pressure inside a torus-shaped core of a vortex ring falls below the vapor pressure of the ambient liquid. By generating a vapor bubble in a rigid tube, a toroidal cavity can be produced outside the tube. The pulsation and propagation behaviors of vortex-ring cavitation are studied using a high-speed video camera and a hydrophone. The experimental results show that the cavity continues to oscillate with a period that depends heavily on the maximal cross-section radius of the cavity and circulation of the vortex flow, under the influence of the surrounding vortex flow field. It is also shown that the cross-radial oscillation of the toroidal cavity can be measured both by a high-speed camera and hydrophone. Moreover, three different methods for estimating the circulation are compared to propose an accurate model of toroidal cavity oscillation. The phenomenon of a toroidal cavity impinging on a fixed wall is also investigated. 相似文献
13.
Reaction thrust of water jet for conical nozzles 总被引：1，自引：0，他引：1
Clear knowledge on the reaction thrust of water jet is valuable for better design of water jet propulsion system. In
this paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry
as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has a
direct proportional relationship with the product of the inlet pressure, the square of flow rate and two-thirds power exponent
of the input power. The results also indicate that the diameter of the cylinder column for the conical nozzle has great influence
on the reaction thrust characteristics. In addition, the best values of the half cone angle and the cylinder column length exist
to make the reaction thrust reach its maximum under the same inlet conditions． 相似文献
this paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry
as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has a
direct proportional relationship with the product of the inlet pressure, the square of flow rate and two-thirds power exponent
of the input power. The results also indicate that the diameter of the cylinder column for the conical nozzle has great influence
on the reaction thrust characteristics. In addition, the best values of the half cone angle and the cylinder column length exist
to make the reaction thrust reach its maximum under the same inlet conditions． 相似文献
14.
Arrangement strategy of ground heat exchanger with groundwater 总被引：2，自引：2，他引：0
The orientation strategy of side pipe and the heat transfer performance of six ground heat exchangers(GHEs) were optimized by numerical simulation,with soil being treated as a porous medium.An experiment on the heat transfer of four GHEs was carried out in 2010.Results indicate that the velocity field is disturbed by GHEs.The optimal orientation strategy of side pipe is that the upward pipe is located upstream and the downward pipe downstream.The space between GHEs should be appropriately adjusted,depending on the direction and flow velocity.Groups of GHEs should be installed perpendicular to the mainstream in a single row,but if the acreage does not meet the requirements,GHEs should be installed in staggered multiple rows.Fewer GHEs parallel to the mainstream strengthen the heat transfer.Moreover,numerical results agree well with the test data,with the maximum relative error being less than 7.7%. 相似文献
15.
喷嘴是水射流切割系统的关键元件，通过研究一级喷嘴直径、二级喷嘴直径、混合腔直径和喉管距、系统工作压力、磨料直径大小等对轴向射流速度的影响，为水切割喷嘴的优化设计奠定了基础，其结果可为高压水切割工具的设计提供参考依据。 相似文献
16.
SMITH Eiamsa-ard PONGJET Promvonge 《浙江大学学报(A卷英文版)》2006,7(8):1406-1415
INTRODUCTION Vortex tube is a device for producing hot and cold air when compressed air flows tangentially into the vortex chamber through the inlet nozzles. This causes the vortex and swirl flow movement inside the vortex tube. The air in the middle region of the tube has lower velocity and lower temperature than the inlet air. So the air near the tube wall has higher ve-locity and higher temperature than the inlet air. The cold air in the core region of the tube flows out through the o… 相似文献
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18.
气固两相流实验装置计算机控制系统 总被引：1，自引：0，他引：1
基于计算机技术和现场总线技术,设计并研制一套计算机控制的气固两相流实验装置。装置采用玉米粉作为固相颗粒,气源的气体经过冷干和稳压,由涡街流量计测量其在不同管道口径的流量。管道内温度和压力信号由变送器送至可编程控制器(PLC)和微型计算机,根据控制参数要求,PLC通过模拟和数字输出口控制气相和固相流量阀门的开闭顺序和流量大小,同时使用现场总线控制变频器,频率大小改变导致给料机的转速改变,进而调节物料流量。比较各种工控网络的优缺点后选定Profibus-DP的通讯方式实现PLC对变频器的控制。实验结果表明,该实验手段先进、操作方便,为教学和科研提供一个良好的实验平台。 相似文献
19.
康国兵 《广东轻工职业技术学院学报》2014,(1):1-5
稀释水调浓水力式流浆箱通过局部调节浆料浓度控制全幅横向定量偏差,采用Realizableκ-ε湍流模,利用数值模拟的方法研究稀释水在布浆支管内与浆流的混合与扩散特性,数值模拟结果与相关试验数据吻合良好;稀释水在浆流中的混合主要通过反向漩涡的逐渐扩散。在入射点近场,稀释水与浆流快速混合,当z/d7后,混合参数M变化趋向平缓,这表明混合速度逐渐降低。在稀释水入射点的下游,距离入射点越远,射流扩散程度越高,混合效果越好;提高稀释水的入射速度,有利于提高混合效果。 相似文献
20.
Sandra Mollenauer Rebecca Bryson Molly Robison Christine Phillips 《Learning & behavior》1992,20(1):25-32
Noise was evaluated as an aversive stimulus in the C57BL/6J mouse, using a simple escape/avoidance procedure in which mice could terminate noise by entering and remaining in a designatedsafe area (corner or side) of a square apparatus. Exposed to pulsed noise of 87.5–90 dB, mice spent 45%–50% of total corner time in the safe corner or approximately 80% of total time in the safe side. Acquisition was significantly faster with moderate intensities of pulsed noise (87.5–90 dB) than it was with high-intensity pulsed noise (100 dB). In comparisons of continuous as opposed to pulsed noise, acquisition was significantly faster with continuous (87.5-dB) noise than it was with pulsed noise, and continuous noise was shown in a choice procedure to be more aversive. Continuous noise caused significant, though not severe, suppression of activity, but pulsed noise caused virtually none. Thus, pulsed noise is a mildly aversive stimuhis for C57BL/6J mice and may have promise for the study of stress-induced behaviors in freely moving animals, but continuous noise is clearly more effective for rapid short-term conditioning. 相似文献