Abstract

The main context of this research is the fluid mechanical analysis of stirred chunky fruit preparations, which are typically highly loaded suspensions (ca. 50%w/w) with particles susceptible to mechanical damage. Knowledge about the transport of such particles in fluid matrices is important in natural and technical processes and can be obtained using optical measurement techniques, e.g. Particle Image Velocimetry. Matching the refractive indices of the relevant material components, a way to ensure signal reliability, is difficult for highly concentrated dispersed systems. Material properties such as plasticity and elasticity of the solid phase and the rheological behaviour of the fluid must be met simultaneously. Fluid motion across the full range of the stirred volume and the immediate surroundings of the stirrer could not be observed without successful refractive index matching of acrylic glass, stirred liquid, and suspended particles. Using the presented materials, the mechanical firmness (but not the resistance against breaking) of soft granular matter can be mimicked. The movement of gel particles in suspensions, their resulting deformation and ultimately, the inflicted damage can be observed with optical methods. The rigidity of the gels may be varied to some extent with the concentrations of the respective hydrocolloids, which, at low concentrations, have no apparent effect on the refractive index. Introducing ethanol, thickeners or other components may yield more degrees of freedom in modelling their flow behaviour.

Graphic abstract

中文翻译：

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液体和半固体材料与丙烯酸玻璃的折射率匹配（RIM），用于光学测量软颗粒物质的力学

摘要

这项研究的主要内容是对搅拌的大块水果制品进行流体力学分析，通常是高负荷的悬浮液（约50％w / w），其颗粒易受机械损伤。在自然和技术过程中，有关此类颗粒在流体基质中的运输的知识很重要，并且可以使用光学测量技术（例如“颗粒图像测速”）获得。对于高度集中的分散系统，匹配相关材料成分的折射率（一种确保信号可靠性的方法）非常困难。必须同时满足材料特性，例如固相的可塑性和弹性以及流体的流变性。没有成功地使丙烯酸玻璃，搅拌的液体和悬浮颗粒的折射率匹配，就无法观察到在整个搅拌体积范围内以及搅拌器周围的流体运动。使用提出的材料，可以模拟软颗粒物质的机械硬度（而不是抗断裂性）。可以通过光学方法观察到凝胶颗粒在悬浮液中的运动，它们导致的变形以及最终造成的破坏。凝胶的刚性可以随相应的水胶体的浓度而在一定程度上变化，在低浓度时，其对折射率没有明显的影响。引入乙醇，增稠剂或其他成分可在建模其流动行为时产生更大的自由度。

图形摘要