科研之友
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摘要
We perform an asymptotic analysis of electrohydrodynamic (EHD) flow of nonpolar liquid subjected to an external, nonuniform electric field. The domain of interest covers the bulk as well as the thin dissociation layers (DSLs) near the electrodes. Outer (i.e., bulk) equations for the ion transport in hierarchical order of perturbation parameters can be expressed in linear form, whereas the inner (i.e., DSL) equations take a nonlinear form. We derive a simple formula in terms of various parameters which can be used to estimate the relative importance of the DSL-driven flow compared with the bulk-driven flow. EHD flow over a pair of cylindrical electrodes is then solved asymptotically and numerically. It is found that in large geometric scale and high ion concentration the EHD flow is dominated by the bulk-charge-induced flow. As the scale and concentration are decreased, the DSL-driven slip velocity increases and the resultant flow tends to dominate the domain and finally leads to flow reversal. We also conduct a flow-visualization experiment to verify the analysis and attain good agreement between the two results with parameter tuning. We finally show, based on the comparison of experimental and numerical solutions, that the rate of free-ion generation (dissociation) should be less than the one predicted from the existing formula.
- 出版日期2013-8-6
