射流作用下吸气流动特性的研究

本文对射流作用下吸气流动的特性做了较全面的研究,即研究了临界射流速度及其影响因素,临界射流出口动量与吸口动量之间的关系,有效作用范围及其影响因素,吸气流场中障碍物对流场特性的影响以及吸气流场轴线吸入速度的衰减特性等。     

射流作用下吸气流场速度分布计算的研究

本文在分析二维射流作用下吸气流动特性的基础上,应用流体力学和复变函数的基本理论和方法。导出射流作用下吸气流场速度分布的分析解。计算结果与实测值吻合较好。     

百叶送风口低温贴附射流的实验研究与分析

测试了百叶送风口低温贴附射流温度分布,确定了其射流轴心温度轨迹。测量了射流轴心速度,回归分析得出了其速度衰减特性公式。提出选择适当的送风速度,在低温送风空调系统中能获得满意的空调效果的观点。     

楔形射流特性的实验研究

通过实验分析了平面楔形射流在不同的楔角及边壁条件下形成的流场特性。研究表明，无论是有边壁的半受限楔形射流，还是无边壁的自由楔形射流，都存在一个临界楔角，偏离此临界角，射流所形成的分散射流都将失稳而成为向上或向下的贴附射流。     

内部诱导型（DY型）旋流风口性能及其应用

综合归纳了一种新型带内部诱导的旋流风口的功能，特性及其应用，给出了不同条件下旋转射流的流型，提供了不同流型的速度分布计算式。为了用于工程设计实践，分析提出了确定诱导比，风口阻力和风口尺寸的详细数据和方法。     

地铁车站敞开楼梯口空气幕挡烟效果测试

通过在某真实的地铁站台开展的全尺寸空气幕挡烟效果实验,研究了不同火源距离下,空气幕出口射流速度和角度对挡烟效果的影响.实验发现,当火源距离楼扶梯口较远时,较小的射流速度和竖直向下的射流角度能起到很好的挡烟效果;当火源距离楼扶梯口较近时,适当增加角度可以有效延长挡烟时间;空气幕出口射流风速取5～7 m/s、倾角取15°～30°时挡烟效果较好;排烟系统开启对烟气蔓延的控制作用优于空气幕,但空气幕并不妨碍排烟系统的排烟效果.     

低速阵列射流强化换热实验与模拟分析

本文对大流动截面、低流动速度工况下,阵列射流对于多个三维加热模块的换热特性进行物理实验与数值模拟研究.验证了在此工况下其强化换热的有效性,通过不同位置模块平均Nu数的大小推得表面平均速度,证明了多孔结构的均流作用对于换热的强化起着重要作用.实验与数值模拟都很好地证明了这一点.本文对多孔结构的几何参数与阻力、换热特性进行了相关研究.     

空气射流,浮力尾流和浮力射流的统一性

论述了空气射流、浮力尾流和浮力射流的相同，相异性及解法特点，归纳分析了现有实验资料。研究表明，空气射流、浮力尾流和浮力射流的轴线流速和剩余温度沿程变化规律可用组合的无量纲参数归化。得到了表征空气射流、浮力尾流和浮力射流轴线速度及温度分布规律的统一公式。     

波流环境下双孔射流的运动和稀释特性

为了研究波流环境下双孔射流的运动和稀释特性,分别采用粒子图像测速(PIV)和平面荧光诱导(PLIF)技术对其速度场和浓度场进行了测量,结合波浪周期性变化的特点对波流环境下射流的运动形态进行了定性分析,同时将波流和横流环境下射流平均速度场和浓度场的分布差异进行了定量比较。结果表明,在波流环境下,部分射流水体周期性地被抛出射流主体形成"云团",使射流分布范围加宽,有助于双孔射流的稀释;相对于横流环境,在波流环境下前方射流对后方射流的遮挡作用大大减小,前、后方射流速度偏转程度均比横流环境更加明显,其迎流面和背流面的浓度分布则更加均匀。     

射流作用下岩石局部渗流压力分布的研究

高压射流辅助破岩在油气井钻井工程中得到广泛应用，其破岩机理还很不明了。本文提出了射流作用下岩石局部范围具有较高渗流压力的思想，并认为该渗流压力大小对射流破岩有重要影响，建立了该渗流压力的计算模型。通过在地面条件下，射流作用于湿砂岩体的多因素数值计算与分析得出：射流的喷射速度大，岩石局部范围内的渗流压力也较大；计算平面的深度位置增加，岩石渗流压力明显减小；压力波（纵波）在岩体中的传播速度变化，对岩石局部范围内的渗流压力影响不大的规律，这对认识岩石在射流作用下的破碎机理有重要意义。     

Modelling and simulation of the near-wall velocity of a turbulent ceiling attached plane jet after its impingement with the corner

At present, ceiling-mounted diffusers are very popular for indoor air distribution, particularly in offices, owing to greater efficiency in the distribution of the air supply and a more comfortable indoor environment. The objective of this study is to construct an effective model to design the indoor airflow of an attached plane jet after its impingement with the corner in a room. In this study, a full-scale test facility was set up to obtain detailed experimental data. One commercial CFD tool, CFX 11.0, was used to simulate the air velocity distribution of an attached plane air jet bounded by the ceiling and an insulated wall. One semi-empirical model was also constructed to predict the impingement jet velocity. The results show that bout the semi-empirical model and CFX 11.0 were able to predict the maximum velocity of an impinging jet at low Reynolds numbers, 1000 and 2000, with an inaccuracy of ±11%. However, the semi-empirical model could be more conveniently used to predict the maximum jet velocity decay after its impingement the corner in a room than CFD simulation in terms of accuracy and the time required to design the indoor airflow pattern.     

百叶风口送风射流的数值模拟

为简化风口入流边界条件的描述,提出用N个简单开口代替不同方向出流的百叶风口,建立了N点风口模型,据此模型对不同出流条件的百叶风口射流进行了数值模拟,并就轴心速度衰减,射流扩展角及断面流速分布等与实验数据进行了对比。结果表明,当N=1或3时,模拟结果令人满意。     

条缝型送风口形成的竖壁贴附射流通风模式研究:送风速度的影响

提出了一种介于混合通风、置换通风之间的新型通风模式——条缝型送风口形成的竖壁贴附射流。利用2DPIV研究了该模式下射流送风速度对气流流场的影响,并对极限贴附距离进行了探讨。研究表明,射流送风速度越大,形成的贴附射流距离越长,贴附效果越显著;同时,送风速度越大,射流对周围空气的卷吸能力越强,射流影响区域越大;射流送风速度的改变对极限贴附距离的影响不明显。     

Numerical comparison of performance between traditional and alternative jet fans in tiled tunnel in emergency ventilation

In this paper a computational study was carried out to evaluate the performance of longitudinal ventilation system equipped with an alternative jet fan with respect to traditional one in case of fire in tiled tunnel. The alternative jet fan is equipped with inclined silencers (pitch angle α = 6°) in order to reduce the Coanda effect and consequently shear stress on the tunnel ceiling. The fire was simulated setting heat flux on HGV surface. Computational fluid dynamic analysis was applied to simulate the ventilation in the unidirectional tunnel through κ–ɛ model. The comparison conducted in terms of total thrust required to prevent back-layering phenomena and numerical results were provided in terms of thrust of jet fan values, average velocity values and temperature profiles, for different tunnel slope values. Furthermore the authors have compared the critical velocity provided by CFD analysis with critical velocity provided in the literature.     

送风口高度对碰撞射流气流特征影响实验研究

通过实验研究了碰撞射流热风供热时不同的送风口高度下室内空气温度、速度和热舒适参数分布情况。分析了送风口高度影响作用,结果表明碰撞射流热风供热系统的送风口高度对室内热环境有显著影响。     

Scale, boundary and inlet condition effects on impinging jets

The sensitivity of the orthonormal impinging jets with respect to scale (Reynolds number), boundary conditions (geometry and surface roughness) as well as inlet conditions is investigated. Due to the unsteady separation in the near-wall region the flow field is Reynolds number dependent. The depth of the boundary layer formed on the impinging surface decreases, while the maximum radial velocity increases with Reynolds number below a critical, Re_cr, value. Above one order of Re_cr the flow becomes asymptotically independent of Reynolds number. When Reynolds number reaches a fully roughness region the depth of the surface layer increases with roughness height only. The flow is found to be only weakly dependent on the distance between the jet and the surface for distances larger than the ring-vortex formation length. Radial confinements of diameters less than approximately 10 jet diameters and axial confinements placed at less than 1 jet diameter above the surface affect the pressure distribution on the impinging plate. The inlet turbulence affects mostly the free-jet flow region.     

大空间空调中射流理论的适用性问题研究

以大空间空调设计中广泛采用的圆形喷口为例,对比分析了传统半经验射流理论计算结果与CFD模拟结果。研究结果表明,模拟得到的多喷口水平并排射流的射流轴心弯曲及轴心风速衰减均较快;实际建筑空间结构、内部发热条件及喷口布置形式对射流的流场有较大影响;空间温度场分布并非仅与射流的射程有关,还受空间整体气流状况影响。