用外加电解质横流抑制电对流和形态不稳定性
Suppression of Electroconvective and Morphological Instabilities by an Imposed Cross Flow of the Electrolyte
摘要：
电对流及其与形态不稳定性的耦合在许多应用中是重要的，包括电渗析、电池和燃料电池。在这项工作中，我们使用两种方法研究了二维通道流对电对流和形态不稳定性的影响。在体分析中，我们考虑了由第二类电渗滑移速度边界条件驱动的电中性体区域的不稳定性，并导出了小波数和大波数的渐近解。在完整的分析中，我们考虑了整个区域的液体电解质和使用超球谱方法数值求解本征值问题。这两项研究表明，施加的流动显着影响的电对流不稳定。施加的流动通过使扰动的离子浓度场变形而产生屏蔽效应，并且阻碍离子从低浓度区域向高浓度区域的转移，从而引起不稳定性。它完全抑制了小波数下的电对流不稳定性，并降低了大波数下扰动的增长率。流动对形态不稳定性的直接影响很小，而电对流不稳定性的抑制可能会改变耦合不稳定性中最不稳定模式的波数。对于电对流不稳定性，在高波数下，体分析与全分析有质的不同。对于形态的不稳定性，发现在小和大波数的两个研究之间的良好协议。
英文摘要：
Electroconvection and its coupling with a morphological instability are important in many applications, including electrodialysis, batteries and fuel cells. In this work, we study the effects of a two-dimensional channel flow on the electroconvective and morphological instabilities using two approaches. In the bulk analysis, we consider the instability of the electroneutral bulk region driven by a second kind electroosmosis slip velocity boundary condition and derive the asymptotic solutions for small and large wavenumbers. In the full analysis, we consider the entire region of the liquid electrolyte and use the ultraspherical spectral method to numerically solve the eigenvalue problems. Both studies show that the imposed flow significantly affects the electroconvective instability. The imposed flow generates a shielding effect by deforming the perturbed ion concentration field and hinders the ion transfer from low- to high- concentration regions which causes the instability. It fully suppresses the electroconvective instability at small wavenumbers and reduces the growth rate of the perturbations at large wavenumbers. The direct effect of the flow on the morphological instability is minor, while the suppression of the electroconvective instability may change the wavenumber of the most unstable mode of the coupled instabilities. For the electroconvective instability, the bulk analysis is qualitatively different from the full analysis at high wavenumbers. For the morphological instability, good agreement is found between the two studies at both small and large wavenumbers.
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