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On the mechanism and prediction of the drag reducing turbulent flow by Toms effect

汤姆斯效应湍流减阻机理及预测

基本信息

批准号：
18560150
负责人：
KURODA Akiyoshi
金额：
$ 2.49万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18560150/
关键词：
drag reduction numerical simulation modeling non-Newtonian fluid Toms effect トムズ効果縦渦運動

项目摘要

The phenomenon of the drag reduction caused by chain polymer molecule or the surfactant which forms the rod-like micelle is known as Toms effect. Our minute discrete element model like dumbbell simulates chain polymer molecule and surfactant. We assumed that the element was in equilibrium for fluctuation of medium and modeled surfactant additive flow. In our previous research(1), we represented the 37% drag reduction can be reconstructed through Direct Numerical Simulation (DNS) of two-dimensional turbulent channel flow. From these results, we consider that the element weakens the longitudinal vortices near wall surface which are bound up with Reynolds stress production and then drag reduction may be caused. In this research, we reconstruct drag reduction phenomenon using our model and observe the interaction between elements and longitudinal vortices by flow visualization using AVS/Express6.1. Then examinations of the mechanism of drag reduction phenomenon and longitudinal vortices decay based on these databases are carried out.In addition study, new character is added on the model, say, the dumbbell element which simulate a polymer can be cut by the stretching force in the fluid. Simulations of 2D channel flows (Re_τ=120-600) are carried out and the drag reduction up to 70% drag reduction rate is reproduced by the modified model

链状聚合物分子或表面活性剂形成棒状胶束，引起的减阻现象称为汤姆斯效应。我们的微小离散元模型像哑铃一样模拟链式聚合物分子和表面活性剂。由于介质波动和模拟表面活性剂添加剂流动，我们假设元件处于平衡状态。在我们之前的研究(1)中，我们表示通过二维湍流通道流动的直接数值模拟（DNS）可以重建37%的阻力减少。从这些结果来看，我们认为该元件削弱了与雷诺应力产生有关的壁面纵向涡，从而可能导致阻力减少。在本研究中，我们利用该模型重构了减阻现象，并利用AVS/Express6.1进行流动可视化，观察了元件与纵向涡的相互作用。然后在此基础上对减阻现象和纵向涡衰减机理进行了验证。在此基础上，增加了模拟聚合物的哑铃单元可以被流体中的拉伸力切割的新特性。对二维通道流动（Re_τ=120-600）进行了模拟，修正模型再现了高达70%的减阻率