Viscous Effects on the Particle Size Segregation in Geophysical Mass Flows: Insights From Immersed Granular Shear Flow Simulations

Abstract

Granular flows composed of differently sized particles tend to segregate into different layers whereby large particles rise to the free surface and small particles settle to the base (Gray, 2018;Umbanhowar et al., 2019). Particle size segregation is an important process in the motion of geophysical mass flows, such as debris flows (

Characteristics of the Impact Pressure of Debris Flows

“…The transition in the dependence of grain segregation on viscosity coincides with the transition of the flow rheology from being dominated by viscous or frictional stresses (Figure 7). This transition is consistent with the numerical simulation of grain segregation using computational fluid dynamics coupled with the discrete element method (K. F. E. Cui et al., 2021). In viscous flows, fluid drag stresses become relevant which weaken contact stress gradients necessary in driving coarse grains upward.…”

“…Gravel with a diameter of 5–8 mm is the segregated debris at the flow front in this study. However, the diameter for grain segregation in natural debris flows with particles ranging from clay to large boulders is still an open question (Cui et al., 2021). The impact pressures of debris flows exerted on structures can be estimated according to a certain weight coefficient for the combination of the SMP and the FP, considering that these two pressures do not peak simultaneously (Figure 10).…”

Mechanisms of the Non‐Uniform Breach Morphology Evolution of Landslide Dams Composed of Unconsolidated Sediments During Overtopping Failure

“…Processes that occur during material transport, such as particle size segregation (C. G. Johnson et al., 2012; K. F. E. Cui et al., 2021), may result in grain sorting in deposits and features such as carapaces (X. Fan et al., 2021).…”

Microscopic Description of Basal Stress Generated by Granular Free‐Surface Flows

“…These parameters are adopted from steady granular flow simulations in the literature and have been found to adequately replicate real granular flow behaviors (Cui et al., 2020; Jing et al., 2020; Silbert et al., 2001). To improve computational efficiency, setting a relatively low value of Young's modulus is commonly adopted (Cui et al., 2021; Tripathi & Khakhar, 2011; Zhou et al., 2020). However, it has been verified that reducing Young's modulus (and holding it constant) does not affect our examination of the dependence of basal stress on the other flow properties (Tripathi & Khakhar, 2011).…”