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Numerical studies on effects of neutrally buoyant large particles
on turbulent channel flow |
| YU Zhao-sheng, WANG Yu, SHAO Xue-ming,WU Teng-hu |
| State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou 310027, China |
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Abstract A direct-forcing fictitious domain method was employed to perform fully-resolved numerical simulations of turbulent channel flow laden with large neutrally buoyant particles. The effects of the particles on the turbulence at the friction Reynolds number of 180 were investigated. The particle volume fractions are 0.79% and 2.36%, respectively. Results show that the presence of particles decreases the maximum rms of streamwise velocity fluctuation near wall via weakening the large-scale streamwise vortices, and on the other hand increases the rms of transverse and spanwise fluctuating velocities in vicinity of the wall via inducing smallerscale vortices. The probability density function (PDF) of the fluctuating velocities near wall was significantly modified by the addition of the particles: firstly, the skewness of the PDF of the streamwise and transverse velocities was reduced, and secondly, the probability for large fluctuating velocities was decreased in the streamwise direction but increased in other two directions. However, the effect of the particles on the velocity PDF normalized with the variance (i.e. rms velocity) is small.
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Published: 01 January 2013
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中性悬浮大颗粒对湍槽流影响的数值研究
采用虚拟区域方法对含有中性悬浮大颗粒的湍槽流进行双重直接数值模拟,研究当摩擦雷诺数为180、颗粒体积分数分别为079%和236%时颗粒对湍流场的影响.结果表明：颗粒的存在削弱了大尺度准流向涡结构,导致近壁处流向脉动速度强度的削弱,且诱导出较小尺度的涡结构,导致近壁处横向和展向脉动速度的增强.颗粒的存在对近壁区脉动速度概率密度分布的影响显著：降低了流向和横向脉动速度概率分布的倾斜度；减小了流向出现大速度脉动的概率,增加了横向和展向出现大速度脉动的概率.对于以方差归一化的脉动速度概率分布,颗粒的影响很小.
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