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Study on the subgrid-scale model taking into account of the viscoelastic effect

考虑粘弹性效应的亚网格尺度模型研究

基本信息

批准号：
14550141
负责人：
HORIUTI Kiyoshi
金额：
$ 2.24万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550141/
关键词：
Large-eddy simulation Subgrid-scale model Nonlinear model Viscoelastic fluid Oldroyd equation Vortical structures Turbulent drug reduction Navier Stokes-Alpha model 渦層-渦管変換粘弾性流体乱流生成削減 N.S.-αmodel Larege-eddy simulation Subgrid-

项目摘要

We begun our study with the generation of the DNS data for the decaying and forced homogeneous isotropic turbulence. Grid points up to 512^3 were employed, and we utilized the SX-5 supercomputer located at the Cyber-media Center, Osaka University, and its user fee was paid by this grant-in aid. In the next step, we investigated on the process of formation of the vortex tube structures along the vortex sheets using the DNS data. We have shown that the tubes are formed through the interaction of the dual vortex sheets, which intersect to each other forming the τ shaped configuration. It was shown that three modes of configuration exist depending on the relative alignment of the vorticity vectors on the two sheets. When the vorticity vectors on the two sheets were placed perpendicular to each other, compression of the strain-rate tensor in the stretching direction arose in the vicinity of the dual sheets. Thus the direction of the axis of the vortex tube generated in this configuration was in the transverse direction against the vorticity vector along the vortex sheet. As the frequency of occurrence of this transformation process increased, intense generation of turbulent energy cascade took place. Then, we investigated the effect of viscoelasticity on the occurrence of this transformation process using the Oldroyd constitutive equation. Using the steady state solution of this equation, we have shown that the viscoelastic effect is primarily exerted on the vortex sheet, and occurrence of its transformation into the tube was annihilated, and the turbulence generation was markedly reduced. It was shown that the steady solution is similar to the nonlinear model which is used in LES of the Newtonian fluid, but to take into the viscoelastic effect in the non-Newtonian fluid, a sign of the one specific term should be reversed.

我们从产生衰减和强迫均匀各向同性湍流的DNS数据开始我们的研究。我们使用了高达512^3的网格点，并使用了位于大阪大学网络媒体中心的SX-5超级计算机，其使用费由这项助学金支付。在下一步中，我们利用DNS数据研究了沿涡片的涡管结构的形成过程。我们已经证明，管子是通过相互交叉的双涡片相互作用而形成的τ形构型。结果表明，根据涡量矢量在两个薄片上的相对排列，存在三种构型模式。当两个薄板上的涡量矢量垂直放置时，拉伸方向上的应变率张量在两个薄板附近出现压缩。因此，在这种构型下产生的涡管轴的方向与涡量矢量沿涡片的横向方向相反。随着这一转化过程发生频率的增加，湍动能级联发生强烈。然后，我们利用Oldroyd本构方程研究了粘弹性对这种转变过程发生的影响。利用该方程的定态解，我们发现粘弹性效应主要作用在涡片上，并消除了涡片向管内转变的发生，湍流的产生明显减少。结果表明，定常解类似于牛顿流体大涡模拟中所用的非线性模型，但要考虑非牛顿流体中的粘弹性效应，应将某一特定项的符号颠倒。