Study on the Subgrid Scale Modeling for Particle-Laden Turbulent Flows

含颗粒湍流亚网格尺度建模研究

基本信息

批准号：
09650189
负责人：
KAJISHIMA Takeo
金额：
$ 2.11万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09650189/
关键词：
Turbulent Flow Multiphase Flow Multiphase Turbulence Gas-Liquid Two Phase Flow Direct Numerical Simulation Large-Eddy Simulation Subgrid Scale Model Computational Fluid Dynamics

项目摘要

We carried out a direct numerical simulation (DNS) of fluid-solid two-phase turbulent flows to consider the subgrid scale (SGS) modeling in the large-eddy simulation (LES) of particle-laden turbulence.First, we developed a finite-difference scheme to resolve the interaction between fluid turbulence and particle motion.In our method, the flow around a solid particle having a length scale several times larger than the spacing of computational grid, is directly simulated.The particle motion is governed by the surface integral of pressure and viscous stress together with the body force such as gravity.This scheme includes no models in fluid turbulence, particle motion or interaction between them.Then, we examined our new method by applying it to the three-dimensional flow past a sphere fixed in a uniform stream.As for the drag coefficient as well as the unsteady vortex shedding, numerical results agreed with experimental results.When the vortex shedding took place, turbulence energy induce … More d through wake was not fully dissipated in the region near a particle.This non-equilibrium nature was enhanced just after the change in drag force of a particle.Next, we simulated a forced isotropic turbulence and turbulent flow in a plane channel including sphere particles.Particles formed larger structure such as clusters, resulting in an additional scale of energy source for fluid turbulence.In an another setup, the relative position of particles was fixed to observe the turbulence modulation without particle clusters.In this case, total energy was sometimes reduced due to the shift of energy spectra into high wavenumber range, even though particles induced extra.In the wall turbulence, particles were distributed non-uniformly in the channel.In this case, the shed vortices was stretched into the streamwise direction due to the velocity gradient, resulted in the production of Reynolds shear stress.These DNS results of particle-laden turbulent flows suggested some important characteristics to be accounted for in SGS modeling.They are non-equilibrium nature due to unsteady vortex shedding, multiple scale of energy injection to fluid turbulence, the modulation in turbulence length scale by particle distribution, and the Reynolds stress production due to the stretch of shed vortices, for example. Less

我们对流固两相湍流进行了直接数值模拟 (DNS)，以考虑颗粒湍流大涡模拟 (LES) 中的亚网格尺度 (SGS) 建模。差分格式来解决流体湍流和粒子运动之间的相互作用。在我们的方法中，直接模拟长度尺度比计算网格间距大几倍的固体粒子周围的流动。粒子运动由下式控制压力和粘性应力以及重力等体力的表面积分。该方案不包括流体湍流、粒子运动或它们之间相互作用的模型。然后，我们通过将其应用于过去的三维流动来检验我们的新方法固定在均匀流中的球体。对于阻力系数以及非定常涡旋脱落，数值结果与实验结果一致。涡旋脱落发生时，湍流能通过尾流诱导的d不完全。在粒子附近的区域中消散。粒子的阻力发生变化后，这种非平衡性质就得到了增强。接下来，我们在包括球体粒子的平面通道中模拟了强制各向同性湍流和湍流。粒子形成了更大的这种结构作为簇，导致流体湍流的能量源的额外规模。在另一种设置中，颗粒的相对位置被固定以观察没有颗粒簇的湍流调制。在这种情况下，尽管粒子引起了额外的能量，但由于能谱移至高波数范围，总能量有时会减少。在壁湍流中，粒子在通道中分布不均匀。在这种情况下，脱落的涡流被拉伸到流向由于速度梯度的影响，导致产生雷诺剪切应力。这些充满颗粒的湍流的 DNS 结果表明了 SGS 建模中需要考虑的一些重要特征。它们是非平衡性质的，因为例如，不稳定涡流脱落、向流体湍流注入多尺度能量、颗粒分布对湍流长度尺度的调制以及由于脱落涡流拉伸而产生的雷诺应力。