In this paper, we propose to explore experimentally the origin of the onset of motion in a well-known Carbopol gel, a concentrated suspension of microgels, when submitted to a vertical temperature gradient, namely, the Rayleigh-Benard Convection (RBC). We consider three possible scenarios: (i) the gel behaves as an elasto-viscoplastic material, (ii) the gel presents a low-stress viscosity μ+ below the yield stress τy, and (iii) the gel can be considered as a two phase system, say the microgels and the solvent, i.e., a porous medium. We propose a complete rheological characterization of Carbopol 940. Creep measurements lead to obtain an instantaneous viscosity plateau μ+∼tm with m≈1. For the first time, we measure and provide permeability values k in the Carbopol gels. We show that k = O(10−14) m2 and k∝τy0.2. Our study focuses on the reference case of the RBC with no-slip conditions at walls, and new results are provided. The results lead to the conclusion that the control parameter is the (inverse) of th...

中文翻译：

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Rayleigh-Bénard 对流在具有屈服应力行为的微凝胶浓缩悬浮液中开始的起源

在本文中，我们建议通过实验探索著名的 Carbopol 凝胶（一种微凝胶的浓缩悬浮液）在垂直温度梯度（即瑞利-贝纳德对流 (RBC)）中运动开始的起源。我们考虑三种可能的情况：(i) 凝胶表现为弹粘塑性材料，(ii) 凝胶在屈服应力 τy 以下呈现低应力粘度 μ+，以及 (iii) 凝胶可被视为二相系统，例如微凝胶和溶剂，即多孔介质。我们提出了 Carbopol 940 的完整流变特性。蠕变测量导致获得瞬时粘度平台 μ+∼tm，m≈1。我们第一次测量并提供 Carbopol 凝胶的渗透率值 k。我们证明 k = O(10−14) m2 和 k∝τy0.2。我们的研究侧重于壁面无滑移条件的 RBC 参考案例，并提供了新的结果。结果得出的结论是，控制参数是...的（倒数）...