Abstract In the present work, an interferometric unsteady analysis of the thermogravitational technique was for the first time attempted in a paralelepipedic microcolumn using binary mixtures with negative Soret coefficients. In particular, water/ethanol and toluene/methanol were considered, as they have significantly different thermophysical properties and relaxation times. Experiments were run with different temperature gradients in order to understand their impact on the stability of separation. Experimental results were compared with theoretical ones, predicted by Fury-Jones-Onsager theory, and by OpenFOAM 3D numerical simulations. Correlations between the separation and the flow in the third dimension perpendicular to the thermal gradient of the thermogravitational microcolumn were analysed. Numerical simulations were also conducted in traditional cylindrical columns in order to compare the results with those previously reported. In these cases, the impact on separation stability was correlated with the azimuthal component of velocity. Thus, in both configurations, the disturbing convective current, always generated in the direction perpendicular to the thermal gradient applied, was shown to be vital for flow stability analysis.

中文翻译：

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热重力效应下的稳定性分析

摘要 在目前的工作中，首次尝试在平行六面体微柱中使用具有负 Soret 系数的二元混合物对热重力技术进行干涉测量非定常分析。特别地，考虑了水/乙醇和甲苯/甲醇，因为它们具有显着不同的热物理性质和弛豫时间。使用不同的温度梯度进行实验，以了解它们对分离稳定性的影响。实验结果与理论结果进行了比较，由 Fury-Jones-Onsager 理论和 OpenFOAM 3D 数值模拟预测。分析了垂直于热重力微柱热梯度的第三维中的分离和流动之间的相关性。还在传统圆柱中进行了数值模拟，以便将结果与先前报告的结果进行比较。在这些情况下，对分离稳定性的影响与速度的方位角分量相关。因此，在这两种配置中，总是在垂直于施加的热梯度的方向上产生的干扰对流电流被证明对于流动稳定性分析至关重要。