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Elucidation and Modeling of Particle Interactions in Dispersed Two-Phase Turbulence

分散两相湍流中粒子相互作用的阐明和建模

基本信息

批准号：
11450073
负责人：
NISHINO Koichi
金额：
$ 2.24万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450073/
关键词：
Multi-Phase Flow Dispersed Two-Phase Flow Turbulent Flow Grid Turbulence Particle Interaction PIV Flow Visualization モデリング画像計測

项目摘要

Turbulence modification by solid particles in grid turlbulence of water is examined experimentally. Glass particles, 2450kg/m^3 in density, are suspended in an upwarl turbulent flow behind a grid with M=12mm. Two particle diameters, d_p=1.00mm and 1.25mm, are examined. The flow velocity is adjusted so that the particles stay quasi-stationary in the test section by the force balance between gravity and drag exerting on the particles. The resultant Reynolds numbers based on Mand d_p are respectively 1660 and 140 for d_p=1.00mm and 2000 and 210 for d_p=1.25mm. Kolmogorov length scales in single-phase flows are 0.43mm Re_M=1740) and 0.40mm Re_M=2000). PIV measurements of turbulence are carried out by using fluorescent tracer particles 26mm in diameter to avoid the effect of strong light scattering by the glass particles. It is found that the turbulence in the streamwise direction increases remarkably and selectively with C, the volumetric concentration of glass particles, in the range of C … More <0.50%. This increase is associated with the occurrence of columnar particle accumulation (CPA) into a region elongated in the streamwise direction. CPA alters significantly the longitudinal two-point velocity correlation, R_uu (Δx) , and vorticity correlation, R_<ω_z><ω_z> (Δx) , while it affects little the transverse two-point velocity correlation, R_vv(Δx), where Δx is the streamwise separation between the two points.Flow visualization is performed to find out particle structures responsible for generation of CPA. It is found that particles tend to accumulate in region being elongated in the streamwise direction at particle volume fraction larger than 0.05%. Probability density functions indicate that the probability for two particles being aligned in the streamwise direction is significantly larger than that in transverse direction. Three-dimensional measurements of particle behaviors made at a condition of low particle volume fraction have revealed a notable interaction between two particles. In the interaction, (1) the downstream particle starts to approach the upstream particle, (2) they suddenly exchange their position whey they come very close to each other, and (3) the downstream particle stays at that position while the upstream particle starts to leave downstream at a relatively high velocity. Less

本文对水的网格湍流中固体颗粒对湍流的影响进行了实验研究。玻璃颗粒的密度为2450 kg/m^3，悬浮在M= 12 mm的网格后的向上湍流中。对两种粒径（d_p=1.00mm和1.25mm）的颗粒进行了检测。调节流速，使得颗粒通过施加在颗粒上的重力和阻力之间的力平衡在测试段中保持准静止。当d_p=1.00mm时，M和d_p的雷诺数分别为1660和140;当d_p =1.25mm时，M和d_p的雷诺数分别为2000和210。单相流动的Kolmogorov长度标度为0.43mm Re_M=1740）和0.40mm Re_M=2000）。湍流的PIV测量是通过使用直径为26 mm的荧光示踪颗粒来进行的，以避免玻璃颗粒的强光散射的影响。结果表明，在一定的浓度范围内，玻璃颗粒的体积浓度C对湍流度有明显的选择性影响 ...更多信息 <0.50%。这种增加是与发生的柱状颗粒的积累（CPA）到一个区域中的流向方向拉长。CPA显著地改变了两点速度的纵向关联R_uu（Δx）和涡量关联R_<ω_z><ω_z>（Δx），而对两点速度的横向关联R_vv（Δx）影响很小，其中Δx是两点间的流向间距。研究发现，当颗粒体积分数大于0.05%时，颗粒倾向于聚集在沿流向伸长的区域。概率密度函数表明，两个粒子在流向排列的概率明显大于横向排列的概率。在低颗粒体积分数条件下对颗粒行为的三维测量揭示了两个颗粒之间的显著相互作用。在相互作用中，（1）下游颗粒开始接近上游颗粒，（2）它们突然交换它们的位置，因为它们彼此非常接近，以及（3）下游颗粒停留在该位置，而上游颗粒开始以相对高的速度离开下游。少