Karatay Elif, Druzgalski Clara L, Mani Ali
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA; Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA.
Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA; Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA.
J Colloid Interface Sci. 2015 May 15;446:67-76. doi: 10.1016/j.jcis.2014.12.081. Epub 2015 Jan 14.
Many microfluidic and electrochemical applications involve chaotic transport phenomena that arise due to instabilities stemming from coupling of hydrodynamics with ion transport and electrostatic forces. Recent investigations have revealed the contribution of a wide range of spatio-temporal scales in such electro-chaotic systems similar to those observed in turbulent flows. Given that these scales can span several orders of magnitude, significant numerical resolution is needed for accurate prediction of these phenomena. The objective of this work is to assess accuracy and efficiency of commercial software for prediction of such phenomena. We have considered the electroconvective flow induced by concentration polarization near an ion selective surface as a model problem representing chaotic elecrokinetic phenomena. We present detailed comparison of the performance of a general-purpose commercial computational fluid dynamics (CFD) and transport solver against a custom-built direct numerical simulation code that has been tailored to the specific physics of unsteady electrokinetic flows. We present detailed statistics including velocity and ion concentration spectra over a wide range of frequencies as well as time-averaged statistics and computational time required for each simulation. Our results indicate that while accuracy can be guaranteed with proper mesh resolution and avoiding numerical dissipation, commercial solvers are generally at least an order of magnitude slower than custom-built direct numerical simulation codes.
许多微流体和电化学应用都涉及到混沌传输现象，这些现象是由于流体动力学与离子传输及静电力耦合产生的不稳定性所导致的。最近的研究表明，在这种电混沌系统中，存在着与湍流中类似的、广泛的时空尺度贡献。鉴于这些尺度可能跨越几个数量级，准确预测这些现象需要很高的数值分辨率。这项工作的目的是评估商业软件预测此类现象的准确性和效率。我们将离子选择性表面附近由浓度极化引起的电对流流动视为一个代表混沌电动现象的模型问题。我们详细比较了通用商业计算流体动力学（CFD）和传输求解器与针对非稳态电动流动的特定物理特性定制的定制直接数值模拟代码的性能。我们展示了包括广泛频率范围内的速度和离子浓度谱以及每个模拟所需的时间平均统计量和计算时间在内的详细统计数据。我们的结果表明，虽然通过适当的网格分辨率和避免数值耗散可以保证准确性，但商业求解器通常比定制直接数值模拟代码慢至少一个数量级。
