Interaction between dry granular flow and rigid barrier with basal clearance: analytical and physical modelling

2020 ◽  
Vol 57 (2) ◽  
pp. 236-245 ◽  
Author(s):  
Clarence Edward Choi ◽  
Charles Wang Wai Ng ◽  
Haiming Liu ◽  
Yu Wang
Keyword(s):  
Granular Flow ◽  
Impact Force ◽  
Particle Diameter ◽  
Physical Modelling ◽  
Impact Model ◽  
Jump Height ◽  
Rigid Barrier ◽  
Physical Experiments ◽  
Dry Granular Flow ◽  
The Impact

Some types of barriers are designed with a clearance between the bottom of the barrier and the channel bed. This feature allows small discharges to pass, thereby reducing the maintenance required over the service life of the barrier. Aside from the practical function of a clearance, it influences the impact force, jump height, and discharge. In this paper, a series of physical experiments was conducted using a 6 m long flume to model the interaction between dry granular flow and rigid barrier with a basal clearance. The ratio between the clearance and particle diameter Hc/D was varied from 0 to 10. The channel inclination was varied from 15° to 35° to achieve different Froude numbers before impact. A new impact model for predicting impact force exerted on the barrier with a basal clearance is presented and evaluated. Results reveal that Hc ≥ 3D is capable of reducing the impact force and overflow. Findings from this study highlight the importance of considering the effects of basal clearance on the design of multiple-barrier systems.

scholarly journals Evaluation of the Impact Force of Dry Granular Flow onto Rock Shed

2019 ◽  
Vol 07 (05) ◽  
pp. 1-15
Author(s):  
Chun Liu ◽  
Zhixiang Yu ◽  
Junfei Huang
Keyword(s):  
Granular Flow ◽  
Impact Force ◽  
Dry Granular Flow ◽  
The Impact

Experimental investigation on the impact force of the dry granular flow against a flexible barrier

Landslides ◽  
2020 ◽  
Vol 17 (6) ◽  
pp. 1465-1483 ◽  
Author(s):  
Xiao Siyou ◽  
Su Lijun ◽  
Jiang Yuanjun ◽  
Qu Xin ◽  
Xu Min ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Granular Flow ◽  
Impact Force ◽  
Flexible Barrier ◽  
Dry Granular Flow ◽  
The Impact

Effects of basal clearance on the impact dynamics of dry granular flow against dual rigid barriers

2021 ◽  
Author(s):  
C.W.W. Ng ◽  
Haiming Liu ◽  
Clarence E. Choi ◽  
Aastha Bhatta ◽  
Min Zheng
Keyword(s):  
Granular Flow ◽  
Impact Force ◽  
Design Guidelines ◽  
New Approach ◽  
Impact Forces ◽  
Physical Model Tests ◽  
Dry Granular Flow ◽  
Current Design ◽  
Maintenance Work ◽  
The Impact

A basal clearance is usually designed beneath barriers to enable sufficient discharge to minimise the maintenance work over service life. Current design guidelines for multiple barriers usually neglect the influence of basal clearance, resulting in either an over-conservative or a non-conservative design impact force acting on the subsequent barriers. In this study, physical model tests were carried out to investigate the effects of basal clearance height (Hc) beneath first barrier on the interaction between dry granular flow and dual rigid barriers. A new approach based on the hydrodynamic equation is proposed to estimate the impact force on the second barrier exerted by the basal discharge from the first barrier. This basal discharge can attenuate the impact force exerted on the second barrier by dissipating the kinetic energy of landing flow and apportioning the load contributions from discharge and overflow. For the first barrier with a barrier height HB1 that was twice of the flow depth h0, the impact force on the second barrier was governed by overflow when Hc/h0 ≤ 0.6 and was dominated by basal discharge when Hc/h0 ≥ 0.8. These two criteria provide a basis for optimising the impact forces for multiple-barrier systems with basal clearances.

scholarly journals Effects of dynamic fragmentation on the impact force exerted on rigid barrier: centrifuge modelling

2019 ◽  
Vol 56 (9) ◽  
pp. 1215-1224 ◽  
Author(s):  
C.W.W. Ng ◽  
C.E. Choi ◽  
D.K.H. Cheung ◽  
Y. Cui
Keyword(s):  
Volume Fraction ◽  
Impact Force ◽  
Inertial Particles ◽  
Size Segregation ◽  
Centrifuge Modelling ◽  
Rigid Barrier ◽  
Flow Energy ◽  
Dynamic Fragmentation ◽  
Large Particles ◽  
The Impact

Bi-dispersity is a prerequisite for grain-size segregation, which transports the largest particles to the flow front. These large and inertial particles can fragment upon impacting a barrier. The amount of fragmentation during impact strongly influences the force exerted on a rigid barrier. Centrifuge modelling was adopted to replicate the stresses for studying the effects of bi-dispersity in a granular assembly and dynamic fragmentation on the impact force exerted on a model rigid barrier. To study the effects of bi-dispersity, the ratio between the diameters of small and large particles (δs/δl), characterizing the particle-size distribution (PSD), was varied as 0.08, 0.26, and 0.56. The volume fraction of the large particles was kept constant. A δs/δl tending towards unity characterizes inertial flow that exerts sharp impulses, and a diminishing δs/δl characterizes the progressive attenuation of these sharp impulses by the small particles. Flows dominated by grain-contact stresses (δs/δl < 0.26), as characterized by the Savage number, are effective at attenuating dispersive stresses of the large particles, which are responsible for reducing dynamic fragmentation. By contrast, flows dominated by grain-inertial stresses (δs/δl > 0.26) exhibit up to 66% more impulses and 4.3 times more fragmentation. Dynamic fragmentation of bi-disperse flows impacting a rigid barrier can dissipate about 30% of the total flow energy.

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