Bianchi Janetti Michele, Janssen Hans
Unit for Energy Efficient Building, Institute for Structural Engineering and Material Sciences, University of Innsbruck (AT), Technikerstrasse 13, 6020 Innsbruck, Austria.
Department of Civil Engineering, Building Physics and Sustainable Design Section, KU Leuven (BE), Kasteelpark Arenberg 40, bus 2447, 3001 Leuven, Belgium.
Transp Porous Media. 2022;142(3):493-508. doi: 10.1007/s11242-022-01754-y. Epub 2022 Mar 3.
We investigate the influence of contact angle variations on spontaneous imbibition of moisture in porous materials. While the contact angle is typically assumed constant when modelling the moisture transfer in porous media, experimental findings put this assumption into question. It has been shown that during imbibition the contact angle notably rises with increasing meniscus velocity. This phenomenon resultantly affects the moisture retention curve, the relation linking the local capillary pressure to the local moisture saturation, which in turn impacts the imbibition rate and moisture distribution. This study investigates these dynamic effects via a pore network technique as well as a continuum approach. It is shown that the impacts of pore-scale contact angle variations on the imbibition process can be reproduced at the continuum scale through a modified moisture retention curve including a dynamic term. Complementarily a closed-form equation expressing the dynamic capillary pressure in terms of local saturation and saturation rate is derived. The continuum approach is then finally employed to predict measured moisture saturation profiles for imbibition in Berea sandstone and diatomite found in literature, and a fair agreement between simulated and measured outcomes is observed.
我们研究了接触角变化对多孔材料中水分自发吸入的影响。在对多孔介质中的水分传输进行建模时，通常假定接触角是恒定的，但实验结果对此假设提出了质疑。研究表明，在吸入过程中，接触角会随着弯月面速度的增加而显著增大。这种现象进而影响了水分保持曲线，即连接局部毛细压力与局部水分饱和度的关系，而这反过来又会影响吸入速率和水分分布。本研究通过孔隙网络技术以及连续介质方法研究了这些动态效应。结果表明，通过包含动态项的修正水分保持曲线，可以在连续介质尺度上再现孔隙尺度接触角变化对吸入过程的影响。作为补充，还推导了一个以局部饱和度和饱和度速率表示动态毛细压力的闭式方程。最后，采用连续介质方法预测了文献中报道的在 Berea 砂岩和硅藻土中吸入时测得的水分饱和度剖面，模拟结果与测量结果之间观察到了较好的一致性。
