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许多火山在喷发时都表现出侵出性和爆破性行为相互转变的特征。我们建立了一个新的理论模型,同时考虑了通道中粘滞力抑制气泡生长造成的气泡压力的积聚过程以及气泡变得连通后气体沿此气泡网逃逸的动力学过程。当气泡与岩浆间的压力差达到气泡化岩浆物质强度时,岩浆将发生破碎。在气体颗粒分散相内颗粒大小的分布特征对流体的影响是通过对能强烈影响此碎裂混合物的声速的两种粒径的颗粒来模拟的。稳态边界值的解呈现出非唯一性。岩浆房内参数固定时至少有两种机制。在低释放率机制里不发生碎屑化,岩浆伴随着部分气体逃逸而上升。这一机制对应着侵出式活动。高释放率机制对应着爆破性活动。使用研讨会上定义的参数的模拟工作对流纹质岩浆组成得到以下结果:岩浆的释放率为5．5×107kg/s,碎屑化面的深度为2 585 m,碎屑化时岩浆的孔隙度为0．74;出口气体速度变化范围为200-450 m/s,取决于岩浆破裂后混合物中小碎屑颗粒的质量分数;出口压力变化范围为1．5-3 MPa。通道直径d在40- 70 m范围内的变化得到的质量流量Q对通道直径的依赖性(d2.8)不像柱形圆管中牛顿液体的粘性流动情况时(Q-d4)那么强烈。随着通道直径的增大,流体中碎屑化将被延迟,通道的阻力保持高数值。岩浆的温度从700℃变至950℃导致的岩浆释放率增加了 4倍,而岩浆的粘度降低了8 000倍以上。
Many volcanoes show the characteristic of mutual transformation between invading and explosive behavior upon eruption. We have established a new theoretical model, taking into account the viscous forces in the channel to suppress the accumulation of bubble pressure caused by bubble growth and the kinetics of gas escape along the bubble network after the bubbles become connected. When the pressure difference between bubbles and magma reaches the strength of the bubble magma material, the magma will crumble. The effect of particle size distribution on the fluid within the gas particle dispersed phase is modeled by particles of two particle sizes that strongly affect the speed of sound of the fragmented mixture. The solution to the steady-state boundary value is non-unique. There are at least two mechanisms for fixed in-magma chamber parameters. No detritus occurs in the mechanism of low release rate, and magma rises along with partial gas escaping. This mechanism corresponds to invading activities. High release rate mechanism corresponds to explosive activity. Using the simulations of the parameters defined at the workshop, the following results were obtained for the rhyolitic magmatic composition: the magma release rate was 5.5 × 107 kg / s, the depth of the clastic surface was 2 585 m, the porosity of the magma at detritalization Degree of 0.74; exit gas velocity range of 200-450 m / s, depending on the mass fraction of small debris particles in the mixture after the rupture of the magma; outlet pressure range of 1.5-3 MPa. The dependence of the mass flow rate Q on the channel diameter (d2.8) resulting from the change of the channel diameter d in the range of 40-70 m is not as strong as the viscous flow of Newtonian liquid in the cylindrical tube (Q-d4). As channel diameter increases, detritus in the fluid will be delayed and channel resistance will remain high. Magmatic temperature changes from 700 ℃ to 950 ℃ resulted in a 4-fold increase in magma release rate and a decrease in magma viscosity by more than 8,000-fold.