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An experimental study on the effect of polymers on the sustaining mechanism of turbulent heat transfer in turbulent water duct flow

聚合物对湍流水管流中湍流传热维持机制影响的实验研究

基本信息

批准号：
11650222
负责人：
HAGIWARA Yoshimichi
金额：
$ 1.66万
依托单位：
Kyoto Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

We developed new techniques for simultaneous visualization of near-wall coherent structure, lumps of entangled polymers and thermal field in a turbulent water duct flow with an introduction of dilute polymer solution from a transverse slot into the buffer region. The main conclusions obtained are as follows.1.The fine particles of fluorescence color, the hydrogen bubbles, dye introduced into the viscous sublayer were found to be effective for the simultaneous visualization for the entangled polymers, the streamwise vortices, and the low-speed streaks, respectively.2.The green-color images contain reflected light from the bubbles, while the red-color images contain fluorescence from the color particles and the dye. Therefore, the motions of bubbles, color particles and dye can be measured independently.3.The eruptive flow induced by the streamwise vortices was measured by applying a PTV technique to the motion of bubbles. It was observed that the evolution of streamwise vortices, and thus the eruptive flow and the lift-up of low-speed streaks were attenuated by the polymer lumps.4.The planer laser-induced fluorescence(PLIF)technique is found to be promising for the measurement of thermal filed in the buffer layer.5.The combination of PLIF, the visualization method with color particles and hydrogen bubbles, and the image-capturing system with two cameras were found to be promising to the simultaneous observation of thermal field, the vortices and the entangled polymers.6.A decrease in the temperature at the buffer layer due to the flow induced by the streamwise vortices was measured. It was observed that the entangled polymers attenuated the generation and evolution of the vortices and thus the aforementioned temperature fluctuation.

我们开发了新的技术，同时可视化近壁相干结构，缠结聚合物块和热场的湍流水管流与稀聚合物溶液从横向槽到缓冲区的介绍。主要结论如下：1.在粘性层中引入荧光色微粒、氢气泡和染料，分别可以有效地同时显示缠结聚合物、流向涡和低速条纹; 2.绿色图像包含来自气泡的反射光，而红色图像包含来自彩色颗粒和染料的荧光。3.将PTV技术应用于气泡的运动，对流向涡引起的爆发流进行了测量。实验结果表明，聚合物块体的存在可以减弱流向涡的演化，从而减弱爆发流和低速条纹的抬升作用; 4.平面激光诱导荧光（PLIF）技术在缓冲层温度场测量中具有良好的应用前景; 5.将PLIF技术与彩色粒子和氢气泡可视化技术相结合，采用双摄像头的图像采集系统可以同时观测温度场、旋涡和缠结聚合物。6.测量了流向涡引起的流动对缓冲层温度的影响。据观察，缠结的聚合物减弱了涡流的产生和演变，从而减弱了上述温度波动。