铝合金板坯连铸过程的DPIV物理模拟

利用先进的数字粒子图像测速技术（DPIV）对铝合金板坯连铸过程中结晶器内的流场进行研究。分析了操作参数以及浮漂漏斗结构对流场的影响。考虑到液固界面的影响,实验采用与枝晶生长结构相似的天然海绵模拟液固界面。结果表明：随着拉坯速度的增大,表面越不稳定;可通过适当增加出水口向下的倾角来提高拉速;跑道形出水口要优于矩形出水口。     

LARGE-EDDY SIMULATION OF FLOW AROUND CYLINDER ARRAYS AT A SUBCRITICAL REYNOLDS NUMBER

The complex three-dimensional turbulent flows around a cylinder array with four cylinders in an in-line square configuration at a subcritical Reynolds number of 1.5 × 10^4 with the spacing ratio at L/D = 1.5 and 3.5 were investigated using the Large Eddy Simulation （LES）. The full field vorticity and velocity distributions as well as turbulent quantities were calculated in detail and the near wake structures were presented. The results show that the bi-stable flow nature was observed at L/D = 1.5 and distinct vortex shedding of the upstream cylinders occurred at L/D = 3.5 at Re = 1.5 × 10^4. The techniques of Laser Doppler Anemometry （LDA） and Digital Particle Image Velocimetry （DPIV） are also employed to validate the present LES method. The results show that the numerical predictions are in excellent agreement with the experimental measurements. Therefore, the full field instantaneous and mean quantities of the flow field, velocity field and vorticity field can be extracted from the LES results for further study of the complex flow characteristics.     

适用致密颗粒团流动的DPIV测试图像处理方法

利用DPIV技术即利用高速摄影和连续激光拍摄获得冷态循环流化床致密颗粒团连续的数字图像,致密颗粒团图像具有曝光过度,灰阶分布不均,颗粒边缘模糊等特点。通过图像分析,在图像前处理、网格划分,匹配原则方面分别采用了色阶调整、边缘增强、多种互相关算法相结合的适用于致密颗粒团DPIV测试图像的处理方法,获得了更高的速度矢量分辨率和精度,并且成功捕捉到了致密颗粒团的聚集和抛散过程中出现的松散小颗粒团的速度矢量。     

Time-resolved vortex wake of a common swift flying over a range of flight speeds

The wake of a freely flying common swift (Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s⁻¹. The wake of the bird is visualized using high-speed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing behind the wingtips, but in addition, a pair of tail vortices and a pair of ‘wing root vortices’ are found that appear to originate from the wing/body junction. The existence of wing root vortices suggests that the two wings are not acting as a single wing, but are to some extent aerodynamically detached from each other. It is proposed that this is due to the body disrupting the lift distribution over the wing by generating less lift than the wings.     

三岔管内水流流动的数值模拟与实验研究

结合江苏宜兴抽水蓄能电站工程建设中钢岔管的设计要求，对分岔角为64°的三岔管内水流的流动进行数值模拟与实验研究。计算中选择SIMPLE方法求解三维雷诺平均方程和k-ε两方程湍流模型，实验采用数字图像测速(DPIV)系统和在试验段前后断面上安装液体差压计对三岔管中心的水平面内的压强差进行测量。研究结果表明，无论水头损失还是三岔管内水流的流动模式，计算与实验吻合得较好，同时反向双管流动较正向双管流动的能量损失大，在相同的流速情况下，单管流动比双管流动的能量损失大，正向单管比反向单管的能量损失大。     

DME闪急沸腾喷雾结构及其发展过程

在环境温度为293 K、压力为0.1 MPa条件下,采用数字粒子图像速度场仪研究了单孔直喷式柴油喷嘴形成的二甲醚(DME)闪急沸腾喷雾的结构及发展过程.为得到喷雾图像,采用Nd:YAG激光光片将喷雾照亮.喷雾图像采用高分辨率的CCD照相机来记录,通过图像采集卡传输到计算机硬盘进行保存.结果表明,DME闪急沸腾喷雾由初始核区、闪急沸腾主体区和涡环形成区3部分组成;根据涡环结构的形成与发展变化,可将DME闪急沸腾喷雾扩展过程分为涡环结构形成、涡环结构发展与变形、涡环结构破碎和闪急沸腾喷雾充分发展4个阶段.     

圆管湍流近壁结构的DPIV实验研究

采用粒子数字图像测速(DPIV)对充分发展的圆管湍流进行了研究，测量结果和直接数值模拟结果的比较，表明作者开发的DPIV技术可取得满意的精度。在此基础上通过瞬时脉动速度场对圆管湍流的近壁结构进行了研究，并在近壁结构中检测出涡诱导的喷发和扫掠、低速条带和流向涡结构等拟序结构，而且发现低速条带和涡的诱导是低速流体喷发的必要条件。     

DPIV技术及其在电厂取水流道物理模型试验中的应用

文中简要回顾了流动显示技术的发展过程，主要对数字粒子图像测速（DPIV）技术的原理、系统的组成及其在电厂取水流道物理模型试验流道流场测量中的应用作了详细介绍，并给出了流道流场的测试结果，指出DPIV技术将会在无接触流场测试中得到广泛应用。     

应用无源仿射模型的DPIV新算法

传统ＤＰＩＶ算法主要于基区域相关运算,此法由于概念简单,操作方便而被广泛接受,但是存在速度慢,错配点多等众所周知的缺点。此文根据ＤＰＩＶ的成像特点以及所研究对象的物理性质,提出了流场的无源仿射模型,结合修改得到的整体不流模型,形成了一种计算ＤＰＶＩ的新方法。