Benzi Roberto, De Angelis Elisabetta, Govindarajan Rama, Procaccia Itamar
Dipartimento di Fisica and INFM, Università Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma, Italy.
Phys Rev E Stat Nonlin Soft Matter Phys. 2003 Jul;68(1 Pt 2):016308. doi: 10.1103/PhysRevE.68.016308. Epub 2003 Jul 23.
Recent direct numerical simulations of the finite-extensibility nonlinear elastic dumbbell model with the Peterlin approximation of non-Newtonian hydrodynamics revealed that the phenomenon of drag reduction by polymer additives exists (albeit in reduced form) also in homogeneous turbulence. We use here a simple shell model for homogeneous viscoelastic flows, which recaptures the essential observations of the full simulations. The simplicity of the shell model allows us to offer a transparent explanation of the main observations. It is shown that the mechanism for drag reduction operates mainly on large scales. Understanding the mechanism allows us to predict how the amount of drag reduction depends on the various parameters in the model. The main conclusion is that drag reduction is not a universal phenomenon; it peaks in a window of parameters such as the Reynolds number and the relaxation rate of the polymer.
最近对有限可伸长非线性弹性哑铃模型进行的直接数值模拟，采用了非牛顿流体动力学的彼得林近似，结果表明聚合物添加剂减阻现象在均匀湍流中也存在（尽管形式有所简化）。我们在此使用一个简单的壳模型来描述均匀粘弹性流动，该模型重现了全模拟的基本观测结果。壳模型的简单性使我们能够对主要观测结果给出清晰的解释。结果表明，减阻机制主要在大尺度上起作用。理解该机制使我们能够预测减阻量如何依赖于模型中的各种参数。主要结论是减阻并非普遍现象；它在诸如雷诺数和聚合物松弛率等参数的一个窗口内达到峰值。
