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Investigation of the convective instability in liquid foam

液体泡沫对流不稳定性的研究

基本信息

批准号：
280187655
负责人：
Dr.-Ing. Sascha Heitkam
金额：
--
依托单位：
Institut für Verfahrenstechnik und Umwelttechnik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/280187655?language=en
关键词：
Investigation convective instability liquid foam

项目摘要

Liquid foam is present in many aspects of our daily life (Cosmetic, Food). Still, we are often surprised and amazed by their unusual behaviour. Maybe thats why foam is a source of inspiration for artists (Tara Donovan: 'Styrofoam Cup Sculpture'), architects (Bejings 'Water Cube') and researchers (John Archibald Wheeler: 'Quantum foam'). In the last three decades we made good progress in investigating liquid foam. Still, many complex effects are not yet well understood. One example for such a complex effect is the 'convective instability'. A small amount of liquid that is added to the upper region of foam will seep downward through the foam uniformly. However, adding a larger amount of liquid will cause flowing of the foam. Similar to a Rayleigh-Taylor instability foam with large liquid content moves downward and foam with a small liquid content moves upward. The appearance of this convective roll was documented more than 15 years ago. However, its mechanism is still not understood. In fact, its shape and features were never surveyed systematically. Only the amount of liquid for its onset has been documented. On this basis, several, partly contradicting theories have been published that explain the onset of the convective instability. In this project, the convective instability will be investigated systematically. To this end, a combination of numerical simulations and experiments will be applied. In the experiment, the convective instability will be measured in vertical channels with different cross-sections and in a wide range of parameters. From the results, a regime-map will be derived, that helps to predict the appearence of the instability in practical applications. The experiments will be combined with phase-averaging numerical simulations that reproduce the convective instability. For this purpose, a flow solver will be extended by effects that take place in realistic foam. To do so, analytical descriptions of the effects are necessary. They will be extracted from literatur, own preliminary work and phase-resolving simulations in the scope of this project. The resulting flow solver is the main tool for explaining the convective instability. The influence of important effects on the instability will be quantified and thus, its mechanism fathomed. Finally, the flow of liquid foam through complex geometries is investigated numerically and experimentally in order to derive a test case for future foam flow investigations in the foam community.

液体泡沫存在于我们日常生活的许多方面(化妆品、食品)。尽管如此，我们还是经常对他们的不同寻常的行为感到惊讶和惊讶。也许这就是为什么泡沫是艺术家(Tara Donovan：《聚苯乙烯泡沫塑料杯雕塑》)、建筑师(北京《水立方》)和研究人员(John阿奇博尔德·惠勒：《量子泡沫》)的灵感来源。在过去的三十年里，我们在研究液体泡沫方面取得了良好的进展。尽管如此，许多复杂的影响还没有被很好地理解。这种复杂效应的一个例子是“对流不稳定性”。加入泡沫上部区域的少量液体将均匀地通过泡沫向下渗透。然而，添加较大量的液体会导致泡沫流动。与Rayleigh-Taylor不稳定性相似，含液量较大的泡沫向下运动，含液量较小的泡沫向上运动。这种对流卷的出现是在15年前被记录在案的。然而，其作用机制尚不清楚。事实上，它的形状和特征从未被系统地调查过。只有发病时的液体量才被记录在案。在此基础上，已经发表了几个部分相互矛盾的理论来解释对流不稳定的开始。在本项目中，将系统地研究对流不稳定性。为此，将采用数值模拟和实验相结合的方法。在实验中，将在不同截面和较大参数范围内测量垂直通道中的对流不稳定性。根据计算结果，得到了一张状态图，有助于预测实际应用中出现的不稳定现象。这些实验将与再现对流不稳定的相平均数值模拟相结合。为此，将通过在真实泡沫中发生的效果来扩展流动解算器。要做到这一点，有必要对影响进行分析描述。它们将从文献中提取，在本项目范围内进行自己的前期工作和相分辨模拟。由此得到的流动解算器是解释对流不稳定性的主要工具。重要效应对不稳定性的影响将被量化，从而揭示其机制。最后，对液体泡沫在复杂几何结构中的流动进行了数值和实验研究，以期为未来泡沫界的泡沫流动研究提供一个测试案例。