Flow resistance in the transition from dense to dilute granular-fluid flows

Song, Dongri; Zhou, Guomei; Chen, Q.

doi:10.1007/s10035-021-01134-1

Cited by 12 publications

(7 citation statements)

References 39 publications

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“…Therefore, b is in the range of viscous flows ( b = 1) and Bagnoldian flows ( b = 2), indicating that both viscous effect and particle collisions contribute to the flow resistance, but the contributions of these two stresses differ. In other words, for Jiangjia Ravine debris flows, the visco‐collisional effect becomes the main mechanism of solid‐fluid interaction (Song et al., 2021) rather than the sustained contact friction in experimental dense two‐phase flows (Iverson, 2000; Pailha & Pouliquen, 2009).…”

Section: Flow Regime and Flow Resistance Of Debris Flowmentioning

confidence: 99%

“…The Darcy number increases with increasing solid concentration (Figure 6a). Debris flows with solid concentrations lower than 0.40 are close to liquefaction (Iverson, 1997; Song et al., 2021); obviously, debris flows with solid concentrations of approximately 0.10 are liquefied. However, to preserve the integrity of the field observation data of the Jiangjia Ravine debris flows, debris flows in the entire solid concentration range (0.10–0.55) is considered in the analysis of the liquefaction state.…”

Section: Field Observation Of Debris Flow At Jiangjia Ravinementioning

confidence: 99%

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Visco‐Collisional Scaling Law of Flow Resistance and Its Application in Debris‐Flow Mobility

et al. 2023

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Flow resistance against gravity‐driven forces is a key factor controlling debris‐flow mobility, which is an important parameter for hazard risk assessment. In practice, Manning's formula is widely used for debris‐flow mobility analysis. However, this formula depends on the boundary conditions (channel roughness) and neglects the physical mechanisms of debris flow. Based on the systematic analysis of the field observation data of 93 debris‐flow events at Jiangjia Ravine (Yunnan Province, China), this study investigates the dynamic mechanisms and sources of flow resistance of debris flow. As the flows tend to be liquefied, the fluid viscous effect and particle collisions are the main sources of flow resistance. Flow resistance can be described by a visco‐collisional scaling law. Under fixed channel boundary conditions, this law is further incorporated into Manning's formula, bridging the gap between the resistance model based on physical mechanisms and the empirical formula of flow resistance. The modified Manning's coefficient is closely related to flow regimes, giving Manning's coefficient an explicit physical meaning. The modified Manning's coefficient provides a more reasonable basis for the mobility analysis and risk assessment of debris flow.

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Section: Flow Regime and Flow Resistance Of Debris Flowmentioning

confidence: 99%

Section: Field Observation Of Debris Flow At Jiangjia Ravinementioning

confidence: 99%

Visco‐Collisional Scaling Law of Flow Resistance and Its Application in Debris‐Flow Mobility

et al. 2023

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“…In this study, the shear rate is deduced based on the flow regime and their corresponding velocity profiles. Specifically, given that particles are fully mixed with the fluid (no sedimentation),

\dot{\gamma }=3v/2h

for the viscous flow profile and

\dot{\gamma }=5v/3h

for the Bagnoldian (inertial) flow profile (Cassar et al., 2005; Song, Zhou, & Chen, 2021). To distinguish the relative dominance of viscous and inertial (particle collision) effects, the “viscous” and “inertial” flow regimes follow the definition of Courrech du Pont et al.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

“…However, with the addition of low solid‐fraction data points, the relationship becomes less significant, indicating that other physical processes start to contribute to the basal shear stress. Recent research has revealed the contribution of visco‐collisional stresses to the macroscopic basal shear stress, especially for those with negligible effective stress (Amarsid et al., 2017; Chen et al., 2023; Song, Zhou, & Chen, 2021). This may form the main source for the basal shear stress of dilute debris flows.…”

Section: Basal Shear Stress Regulated By Granular Dilatancy and Pore‐...mentioning

confidence: 99%

Impact Behavior of Dense Debris Flows Regulated by Pore‐Pressure Feedback

Song,

Chen,

Sadeghi

et al. 2023

JGR Earth Surface

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The impact dynamics of dilute debris flows (typically volumetric solid fractions<50%) have been extensively investigated within the framework of hydraulics. For dense debris flows, the impact mechanisms have been poorly studied. From a geotechnical viewpoint, the feedback between granular dilatancy and pore‐pressure response may play an important role in the dense debris‐flow regime. In this study, the impact behavior of dense and dilute debris flows in an instrumented flume is analyzed. The basal stresses (normal/shear stresses, pore‐fluid pressure) and impact pressure on a rigid barrier are measured. A time‐dependent creeping mode is observed for the impact process of slow‐moving dense debris flows, which cannot be accurately estimated using current debris‐flow load models. At the grain scale, this macroscopic creeping mode is a result of the feedback between granular dilatancy and pore‐pressure response. This feedback can be further characterized by examining the timescales associated with pore‐pressure generation and dissipation. The regulation of pore‐pressure feedback on basal shear stress, impact load, and state of static deposit is revealed. Finally, a tentative phase diagram is proposed for dense and dilute debris‐flow impact. The proposed framework complements the theory for debris‐flow impact loads.

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“…It helps explain why k and C d decrease in the increase of slope angle. Since the dynamic tensile strength of the metal tow is about 1.1 to 1.2 times the static tensile strength [27], it is not necessary to increase the tensile strength of the support rope for the granular flow of uniform particle gradation, similar initial mass and potential energy, and the flow depth is more than twice the average particle size. It is relatively difficult to control gradation only in physical experiments rather than the bulk densities and the angles of repose.…”

Section: Plos Onementioning

confidence: 99%

Effects of flow regimes on the interaction between granular flow and flexible barrier

Xiao,

Xu,

Wang

et al. 2023

PLoS ONE

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Flexible barriers are widely used to mitigate granular flows. In practice, flow regimes may keep changing along a flow path after the initiation of granular flows. The effects of flow regimes should be considered in the design of flexible barriers to intercept granular flow. In this study, flow regimes are divided into three types: dilute flow; dense flow; and quasistatic flow. The impact mechanisms of dense granular flows and dilute granular flows against flexible barriers are investigated using flume tests and the discrete element method. Influences of the ratio of the average particle size to the mesh size of a flexible barrier and particle segregation on the interaction between the flexible barrier and the granular flow are revealed. Differences of the impact mechanisms between rockfall and granular flow are compared. Results show that the impact force of dense granular flow against a flexible barrier will not increase linearly with the average particle size. The tensile force of the bottom cable is usually the maximum tensile force among all cables of the flexible barrier. Particle segregation will lead to increase in impact force of dense flows and tensile force of the upper cables. Impact force of the dilute granular flow increases with the average particle size. Different from the failure of a flexible barrier under the impact of the dense flow, the middle and upper cables are easier to break. Based on these findings, a useful reference for the future design of flexible barriers was proposed.

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Flow resistance in the transition from dense to dilute granular-fluid flows

Cited by 12 publications

References 39 publications

Visco‐Collisional Scaling Law of Flow Resistance and Its Application in Debris‐Flow Mobility

Visco‐Collisional Scaling Law of Flow Resistance and Its Application in Debris‐Flow Mobility

Impact Behavior of Dense Debris Flows Regulated by Pore‐Pressure Feedback

Effects of flow regimes on the interaction between granular flow and flexible barrier

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