Particle-fluid interactions in a plane near-wall turbulent flow
Particle-fluid interactions in a plane near-wall turbulent flow
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DOI：
10.1017/s0022112004008304
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发表时间：
2004-04-25
影响因子：
3.7
通讯作者：
Romano, GP
中科院分区：
文献类型：
--
作者：
Righetti, M;Romano, GP
本文研究了比流体重的颗粒（水中的玻璃球）在光滑床面上明渠紊流中的作用，其体积浓度约为10（-3）。本工作的重点是在近壁区的固体（颗粒）和流体相之间的动力学相互作用。实验测量已通过相位多普勒风速仪同时获得两个速度分量，颗粒尺寸和浓度的数据进行，流动的雷诺数接近15 000。观察到，在含颗粒流中，流向平均速度（对于流体和固体相）的垂直分布在外层中减小（y（+）> 20），但在粘性子层中增加（y（+）< 5）与清水条件相比，导致靠近壁面的明显滑动运动边界条件（y（+）接近2）。此外，在存在固体颗粒的情况下，流动在靠近壁（y（+）< 15）处表现出小于颗粒的速度，而在外层中则相反。在载有颗粒的流动中，y（+）> 10-20（取决于颗粒惯性）时，顺流方向的湍流强度，尤其是垂直速度的湍流强度会减弱，但在非常近壁的区域（y（+）< 5）会增强，雷诺应力也是如此。这些发现可以解释，如果他们提到的机制，颗粒夹带和沉积，这发生在靠近壁。这种机制与颗粒惯性和近壁湍流结构的动态有关，近壁湍流结构将缓冲区和外部区域与非常近壁区域连接起来。雷诺应力的象限分析揭示了两相之间的动量交换，这在缓冲区是特别有效的。
The role of particles heavier than the fluid (glass spheres in water) in a turbulent open channel flow over a smooth bed is examined at volume concentration about 10(-3). The present work focuses on the dynamical interaction between the solid (particles) and the fluid phases in the near-wall region. Experimental measurements have been performed by means of phase Doppler anemometry to acquire two velocity components, particle size and concentration data simultaneously; the Reynolds number of the flow was close to 15 000. It is observed that in the particle-laden flow, the vertical profiles of the streamwise mean velocity (for both fluid and solid phases) are reduced in the outer layer (y(+) > 20), but increased in the viscous sublayer (y(+) < 5) in comparison to the clear-water conditions, leading to an apparent slip kinematic boundary condition close to the wall (y(+) approximate to 2). Moreover, in the presence of solid particles, the flow exhibits a velocity close to the wall (y(+) < 15) which is smaller than that of the particles, while in the outer layer the opposite takes place. In particle-laden flow, turbulence intensities of the streamwise and especially of the vertical velocity are damped for y(+) > 10-20 (depending on particle inertia) but enhanced in the very near-wall region (y(+) < 5), as is the Reynolds stress. These findings can be explained if they are referred to the mechanism of particle entrainment and deposition, which takes place close to the wall. This mechanism is related to particle inertia and to the dynamic of the structure of near-wall turbulence, which connects the buffer and outer regions with the very near-wall region. A significant momentum exchange between the two phases, which is particularly effective in the buffer region, is revealed by the quadrant analysis of the Reynolds stresses.