Experimental Rheology of Magmatic Emulsions and Foams: Effects of Composition, Temperature, Shear Rate and Bubble Content

9972922 Spera含气泡岩浆的流变学性质具有重要的基础和实际意义。 由于气泡是可变形的，因此气泡形状在流动期间改变，这导致乳液（熔体+蒸汽）的剪切速率依赖性粘度。在低剪切速率下，气泡保持表面张力主导的球形形状，并且乳液粘度与无气泡熔体粘度的比率随着气泡含量的增加而增加。在高剪切速率下，情况正好相反;随着气泡含量的增加，乳液的粘度相对于熔体降低。由于少量的挥发性成分，如H2O和CO2在岩浆中普遍存在，而且这些化合物的溶解度很低，因此几乎所有的岩浆在低压和喷发时都变得挥发饱和（因此是起泡的）。使用专门为此目的制造的高扭矩精度同心圆筒粘度计定量岩浆乳状液和泡沫的流变特性作为温度、剪切速率、气泡含量和熔体组成的函数，将提供关于起泡岩浆的流变特性的基本信息。 这些流变学数据将总结发展本构关系，可用于物理火山建模研究，将fillan重要的差距，我们的知识，关于岩浆的粘度特性。

9972922SperaThe rheological properties of bubble-bearing magmas are of interest for fundamental as well as practical reasons. Because bubbles are deformable, bubble shapes change during flow and this gives rise to a shear-rate dependent viscosity for the emulsion (melt + vapor). At low shear rate, bubbles retain a surface tension -dominated spherical shape and the ratio of the emulsion viscosity to the bubble-free melt viscosity increases as the bubble content increases. At high rates of shear just the opposite occurs; the viscosity of the emulsion decreases relative to the melt as the bubble content increases. Because small amounts of volatile components such as H2O and CO2 are ubiquitous in magmas and because these compounds are sparingly soluble, virtually all magmas become volatile-saturated (hence bubbly) at low pressure and upon eruption. Quantification of the rheological properties of magma emulsions and froths as a function of temperature, shear rate, bubble-content and melt composition using a high torque precision concentric cylinder viscometer specifically fabricated for this purpose will provide basic information concerning the rheological properties of bubble-beraing magmas. These rheological data will be summarized by developing constitutive relations that can be used in physical volcanological modelling studies and will fillan important gap in our knowledge regarding the viscometric properties of magma.