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首页> 外文期刊>International Journal of Heat and Mass Transfer >Numerical study of unsteady, thermally-stratified shear flows in superposed porous and pure-fluid domains
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Numerical study of unsteady, thermally-stratified shear flows in superposed porous and pure-fluid domains

机译：多孔和纯流体叠加区中非稳态热分层剪切流的数值研究

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摘要

In this paper we report on numerical simulations of temporally evolving, thermally stratified shear flows in superposed porous and pure-fluid domains. In particular, we study two different types of flows, namely, pressure-driven channel flows and unforced shear layers. Our study is based on a recently developed thermo-mechanical model for flows in the domains of interest. This model follows a mixture-theoretic approach, according to which the medium's porosity is introduced as a concentration parameter, thus allowing the derivation of a single set of equations that is valid simultaneously in both domains. For the types of flows examined herein, our simulations predict the formation of spanwise vortical structures (rollers) at the porous-pure fluid interface. These rollers grow in time thereby inducing fluid circulation inside the porous medium. For the case of pressure-driven channel flows, our simulations further predict the development of plumes of hot and cold fluid due to convective instabilities that interact with the rollers. In the case of unforced shear layers, unstable stratification accelerates the growth of the rollers, which soon start to merge, and enhances fluid mixing. By contrast, the effect of stable stratification is exactly the opposite. Herein we discuss in detail the temporal evolution of the predicted flow structures and the interactions between them, as well as the mechanisms that induce thermal non-equilibrium inside the porous medium.
机译：在本文中，我们报告了在重叠的多孔和纯流体域中随时间演化的热分层剪切流的数值模拟。特别是，我们研究了两种不同类型的流动，即压力驱动的通道流动和无力剪切层。我们的研究基于最新开发的热力学模型，用于关注领域中的流动。该模型遵循混合理论方法，根据该方法，将介质的孔隙率作为浓度参数引入，因此可以导出在两个域中同时有效的单组方程。对于本文中检查的流动类型，我们的模拟预测了在多孔纯流体界面处的展向涡旋结构（滚柱）的形成。这些辊随着时间增长，从而引起多孔介质内部的流体循环。对于压力驱动的通道流，我们的模拟进一步预测了由于与滚子相互作用的对流不稳定性，冷热流体羽流的发展。在未受力的剪切层的情况下，不稳定的分层会加速滚子的生长，并很快开始融合并增强流体混合。相比之下，稳定分层的效果恰好相反。在这里，我们详细讨论了预测的流动结构的时间演化及其之间的相互作用，以及在多孔介质内部引起热不平衡的机制。

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