摘要
现有文献对于粒子对湍流的调制已经进行了严格的研究,在不同的空间长度尺度上产生了湍流动能的减小或增强.然而,由于界面力的存在,对多相流中湍流调制的一般描述没有引起足够的重视.本文用解析和数值方法研究了界面和流体颗粒流的湍流调制,其中表面张力和阻力分别定义了界面相耦合.结果表明,表面张力和表面阻力在湍流动能的输运方程中是附加的产生/耗散项,这对多相流的湍流模拟特别重要.此外,我们还研究了两种类型的多相流在衰减均匀各向同性湍流中的湍流调制.结果表明,在这两种情况下,能量在大尺度上减小,而小尺度能量比单相流增强.特别是,在大尺度下,表面张力作用于湍流涡流,并阻碍了水滴从波纹界面的喷射.相反,在小尺度上,表面张力和速度波动是一致的,导致能量的增强.在流体-粒子流的情况下,粒子在小尺度上比周围流体保持更长的能量,而在大尺度上粒子并不完全遵循周围流体减少能量的规律.对于后者的效果,相当依赖于粒子斯托克斯数.
The modulation of turbulence by particles has been rigorously investigated in the literature yielding either a reduction or an enhancement of the turbulent kinetic energy at different spatial length scales.However,a general description of the turbulence modulation in multiphase flows due to the presence of an interphase force has attracted less attention.In this paper,we investigate the turbulent modulation for interfacial and fluid-particle flows analytically and numerically,where surface tension and drag define the interphase coupling,respectively.It is shown that surface tension and drag appear as additional production/dissipation terms in the transport equations for the turbulent kinetic energies(TKE),which is of particular importance for the turbulence modelling of multiphase flows.Furthermore,we study the modulation of turbulence in decaying homogenous isotropic turbulence(HIT)for both types of multiphase flow.The results clearly unveil that in both cases the energy is reduced at large scales,while the small-scale energy is enhanced compared to single-phase flows.Particularly,at large scales surface tension works against the turbulent eddies and hinders the ejection of droplet from the corrugated interface.In contrast,at the small scales,the surface tension force and the velocity fluctuations are aligned leading to an enhancement of the energy.In the case of fluid-particle flows,particles retain their energy longer than the surrounding fluid increasing the energy at the small scales,while at the large scales the particles do not follow exactly the surrounding fluid reducing its energy.For the latter effect,a considerable dependence on the particle Stokes number is found.
基金
This work was supported by the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development. The authors further want to acknowledge the funding support of K1-MET GmbH, metallurgical competence center. The research programme of the K1-MET competence center is supported by COMET (Competence Center for Excellent Technologies), the Austrian programme for competence centers. COMET is funded by the Federal Ministry for Transport, Innovation and Technology, the Federal Ministry for Digital and Economic Affairs and the provinces of Upper Austria, Tyrol and Styria. Beside the public funding from COMET, this research project is partially financed by the industrial partners Primetals Technologies Austria GmbH, voestalpine Stahl Donawitz GmbH, RHI Magnesita GmbH and voestalpine Stahl GmbH.
