Pattern Formation by Fracturing in Visco-elastic Materials

粘弹性材料断裂形成图案

• 批准号: 04804023
• 负责人: OGAWA Tohru
• 金额: $ 1.15万
• 依托单位: University of Tsukuba
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04804023/
• 关键词: visco-elasticity; visco-elastic fingering; fracture; pattern formation; fractal

A pattern growth of the injection fluid into visco-elastic materials was studied in two dimensional system. Ager gels were used as model materials of visco-elastic materials. A Hele-Shaw cell filled with the ager gel was used in the injection experiments. By changing ager contents of the ager solution, the visco-elastic property of the ager gel changes from one of viscous fluids to one of elastic solids. At the case of lower contents of ager solution (lower than 0.1 weight percent), ager gels behave like viscous fluids. The higher ager contents, the more elastic property ager gels will gain. Therefore, we can control visco-elastic property of model materials by changing the ager contents. Air is used as an injection fluid in our experiments. With changing the ager contents and the injection pressure, systematic pattern formation experiments were carried out under a constant injection pressure. Pattern growth during experiments was measured by CCD video camera. The pattern grows in the condition of outside equilibrium. Both viscous flow and elastic cracking are control mechanisms in our pattern growth. Viscous fingering is a well known phenomena : when a lower viscosity fluid is injected into Hele-Shaw cell filled with highly viscous fluid. The growth of viscous fingering is a quasi static growth. In the case of elastic solid, the pattern is controlled by fracturing. Hydro-fracturing, e.g.crack eruption in volcano, is one of the typical examples. In our system, a new type of pattern growth was observed. This pattern was generated under two competitive mechanisms ; cracking and viscous flow. We coined this new pattern as a visco-elastic fingering. Morphological phase diagram was obtained. At the lower injection pressure and lower ager contents, viscous fingering will appera. When we used higher contents ager gels, a single plane crack growth is observed. At the middle of the range, visco-elastic fingering is observed.

在二维系统中研究了粘弹性材料中注入流体的斑图生长。Ager凝胶作为粘弹性材料的模型材料。在注射实验中使用填充有琼脂凝胶的Hele-Shaw池。通过改变老化剂溶液中的老化剂含量，使老化剂凝胶的粘弹性由粘性流体变为弹性固体。在较低含量的老化剂溶液（低于0.1重量%）的情况下，老化剂凝胶表现为粘性流体。老化剂含量越高，老化凝胶的弹性越大。因此，可以通过改变老化剂的含量来控制模型材料的粘弹性。在我们的实验中使用空气作为注入流体。通过改变老化剂含量和注入压力，在恒定注入压力下进行了系统的井网形成实验。利用CCD摄像机对实验过程中的图形生长进行了测量。这种模式是在外部均衡条件下生长的。粘性流动和弹性开裂是我们的图案生长的控制机制。粘性指进是一种众所周知的现象：当低粘度流体注入充满高粘度流体的Hele-Shaw盒时。粘性指进的增长是准静态增长。在弹性固体的情况下，图案由断裂控制。水力压裂，如火山裂隙喷发，就是其中的一个典型例子。在我们的系统中，观察到一种新的模式生长。这种模式下产生的两个竞争机制;开裂和粘性流动。我们把这种新的模式称为粘弹性指进。得到了相态图。在较低的注入压力和较低的胶凝剂含量下，会出现粘性指进现象。当我们使用较高含量的老化凝胶时，观察到单一平面裂纹扩展。在中间的范围内，粘弹性指进观察。