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中文核心期刊

壁面展向震荡诱导颗粒湍槽流减阻的直接数值模拟研究

DRAG REDUCTION OF PARTICLE-LADEN CHANNEL FLOW BY SPANWISE WALL OSCILLATION: A DIRECT NUMERICAL SIMULATION

  • 摘要: 对湍槽流的减阻研究具有科学意义和工程应用价值, 已有大量研究表明向单相湍流中添加离散物质是一种有效的被动减阻方法. 相比于被动减阻技术, 主动减阻技术如壁面震荡减阻的可控性更高, 近年来也得到广泛的关注, 但对于壁面展向震荡诱导减阻的研究主要针对单相湍槽流, 还未见有相关研究将这一手段用于含颗粒湍槽流的减阻. 因此, 文章采用直接数值模拟方法开展了壁面展向震荡诱导颗粒湍槽流减阻的机理研究. 一方面关注壁面震荡对颗粒湍槽流的调制效果及机理. 另一方面关注颗粒和震荡对单相湍槽流的耦合减阻效应. 结果表明: 壁面震荡可以达到有效减阻, 存在最优震荡周期使减阻率达到最大, 且最优震荡周期与单相流结果相近. 在相同体积分数下, 施加壁面震荡的小颗粒湍槽流减阻效果更好. 相比于单相湍槽流, 当震荡周期小于最优周期时, 震荡和颗粒的耦合效应对减阻率的额外贡献较小且可能为负, 当大于最优周期时额外贡献逐渐增大, 对整体减阻率的占比最高可达10%左右.

     

    Abstract: Study on drag reduction of turbulent channel flow has its significance in both scientific researches and industry applications. The passive drag reduction technique that has been reported to be effective is to add dispersed materials into the single-phase turbulence. On the other hand, the active drag reduction technique, i.e., spanwise wall oscillation, which can be controlled in advance, has attracted wide attention in recent years. Drag reduction induced by spanwise wall oscillation has been successfully applied to single-phase turbulence, however, there is few attentions is paid to the drag reduction of particle-laden channel flow by the aforementioned active technique. Therefore, the drag reduction of particle-laden channel flow by spanwise wall oscillation is studied in this paper by direct numerical simulations. The major concern is two-folded: the first is the turbulent modulation and mechanism of particle-laden channel flow induced by spanwise wall oscillation, and the second is the coupling effect of laden particles and wall oscillation on drag reduction. Comparing with non-oscillation particle-laden channel flow, the wall drag of particle-laden channel flow is reduced by spanwise wall oscillation. The optimal oscillation period is found to achieve the maximum drag reduction rate, which is similar with the trend of single-phase channel flow. With the same volume fraction, channel flow with small size particle exhibits large drag reduction. Comparing with non-oscillation single-phase turbulence, for small oscillation period scenario the coupling contribution of laden particles and wall oscillation has weak and even negative effect on drag reduction, as the oscillation period increases the coupling contribution becomes significant and the maximum magnitude is around 10% of the overall drag reduction.

     

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