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A Study on the Mechanism of Reduction of Turbulence Generation in Viscoelastic Fluid

减少粘弹性流体湍流产生机理的研究

基本信息

批准号：
16560136
负责人：
HORIUI Kiyosi
金额：
$ 2.18万
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：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16560136/
关键词：
Turbulent drag reduction Polymer-diluted fluid Constitutive stress equation Direct numerical simulation Johnson-Segalman equation Affinity of polymer strand Homogeneous isotropic tuebulence Pipe flow DNS JS方程式 rotating-disk apparatus /

项目摘要

We studied the effect of non-affinity in the viscoelastic fluid on the process of the vortical structure formation and reduction of turbulence generation. We dealt with the homogeneous isotropic turbulence and the turbulence in the pipe flow, and utilized the numerical data which were generated using the direct numerical simulation method. The non-affine effect on the polymer stress was approximated using the Johnson-Segalman constitutive equation (Johnson and Segalman 1977, JS model). In both isotropic and pipe flows, the degree of reduction of the turbulence generation was not monotonic on the strength of the non-affinity. The largest reduction of turbulence generation was achieved when the non-affine effect was largest, i.e., the Oldroyd-A equation, and the smallest reduction when the non-affine effect was smallest, i.e., the Oldroyd-B equation. Mechanism of this reduction was examined by looking into the formation of the vortical structures. It was shown that the concentration of the polymer stress was largest in the tube core region in the Oldroyd-B equation and the growth of the vortex tube core region was attenuated, whereas the concentration was largest in the vortex sheet region in the Oldroyd-A equation, thus the transformation of the vortex sheet into the vortex tube was annihilated. A theoretical analysis on the JS model was carried out using the algebraic approximate steady solution of the model. It was shown that the 2^<nd>-order solution does not yield a non-monotonic growth of the turbulence generation reduction. This drawback was mitigated in the solutions with 3^<rd> or higher orders.

研究了粘弹性流体中的非亲和性对涡结构形成和湍流减弱过程的影响。采用直接数值模拟方法，对均匀各向同性湍流和管内湍流进行了数值模拟。使用Johnson-Segalman本构方程（约翰逊和Segalman 1977，JS模型）来近似对聚合物应力的非仿射效应。在各向同性和管流中，湍流产生的减少程度不是单调的非亲和力的强度。当非仿射效应最大时，即，Oldroup-A方程，以及当非仿射效应最小时的最小减少，即，奥尔德罗夫-B方程这种减少的机制进行了研究，通过寻找到涡结构的形成。结果表明，在Oldrophil-B方程中，聚合物应力集中在管芯区最大，涡管芯区的增长被削弱;而在Oldrophil-A方程中，聚合物应力集中在涡面区最大，涡面向涡管的转化被消灭。利用JS模型的代数近似定常解对模型进行了理论分析。结果表明，2^<nd>-阶解不产生湍流生成减少的非单调增长。这个缺点在具有3阶或更高阶的解决方案中得到缓解<rd>。