Impact force of granular flows on walls normal to the bottom: slow versus fast impact dynamics

2021 ◽  
Vol 58 (1) ◽  
pp. 114-124
Author(s):  
T. Faug
Keyword(s):  
Flow Regime ◽  
Impact Force ◽  
Granular Flows ◽  
Analytic Solutions ◽  
Impact Dynamics ◽  
Small Scale ◽  
Incoming Flow ◽  
Mass Flows ◽  
Fast Flow ◽  
The Impact

The devastating effects of natural hazards due to the propagation of mass flows, such as landslides, debris flows, and avalanches, can be avoided, or at least reduced, by placing protective barriers or catching dams in the runout zones. Such structures can store the whole mass and finally stop the flow before it may reach vulnerable infrastructures. Their design requires the modelling of the runup of granular flows on rigid walls and the induced impact force. In this study, careful attention is paid on how the incoming flow regime (either slow or fast flow) that takes place before the impact with the wall can drive the prevailing process at stake during the impact of the flow with the wall. Slow flows produce gentle pile-up of the mass behind the wall with gradually varied streamlines, while faster flows give rise to a granular jump traveling upstream. Two different analytic solutions are proposed and checked against recent small-scale laboratory tests by Ashwood and Hungr (2016), who investigated both slow and fast impact dynamics of granular flows against a wall. This allows to clarify the intertwinned relation between the incoming flow regime and the induced impact force, thus providing crucial information for the geotechnical engineers in charge of the design of mitigation structures against mass flows and mountain hazards.

Effects of Obstacle’s Curvature on Shock Waves in Gravity-Driven Experimental Flows Impacting a Circular Cylinder or a Wall

2020 ◽  
Author(s):  
Zheng Chen ◽  
Siming He ◽  
Dieter Rickenmann
Keyword(s):  
Shock Wave ◽  
Circular Cylinder ◽  
Pressure Sensors ◽  
Granular Flows ◽  
Impact Pressure ◽  
Small Scale ◽  
Cylinder Surface ◽  
Seismic Signals ◽  
Dynamic Impact ◽  
The Impact

<p>Geophysical granular flows such as rock and snow avalanches, flow-like landslides, debris flows, and pyroclastic flows are driven by gravity and often impact on engineering structures located in gullies and slopes as they flow down, generating dynamic impact pressures and causing a major threat to infrastructures. It is necessary to understand the physical mechanism of such granular flows impacting obstacles to improve the design of protective structures and the hazard assessment related to such structures. In this study, the small-scale laboratory experiments were performed to investigate the dynamic impact caused by granular flow around a circular cylinder with variable radius of curvatures and the dynamic impact against a flat wall. Pressure sensors were used to measure the impact pressure of granular flows at both the upstream cylinder surface and at the bottom of the channel. Accelerometers were mounted on the underside of channel to record the seismic signals generated by the granular flows before and during the impact with the obstacle. Flow velocities and flow depths were determined by using high-precision cameras. The results show that a bow shock wave is generated upstream of the cylinder, causing dynamic pressures on both the obstacle and the bottom of the channel. The dimensionless standoff distance of the granular shock wave decreases nonlinearly or almost exponentially with increasing Froude number (Fr) in the range of 5.5 to 11.0. The dimensionless pinch-off distance and dimensionless run-up height grow linearly with increasing Fr, and they were significantly influenced by the radius of curvature of the structure at the stagnation point (RCSSP). The dimensionless impact pressure on the structure surface is sensitive to the RCSSP, while the differences decrease as Fr increases; Seismic signals generated at the underside of the channel and at the top of the cylinder were also recorded to assist in analyzing the effects of RCSSP.</p>

Numerical Modeling of Dynamic Inelastic Response of Clamped Rectangular Plates Impacted by a Knife-Edge Indentor

1991 ◽  
Vol 113 (4) ◽  
pp. 312-319 ◽  
Author(s):  
L. Zhu ◽  
D. Faulkner
Keyword(s):  
Rectangular Plate ◽  
Impact Force ◽  
Small Scale ◽  
Rectangular Plates ◽  
Knife Edge ◽  
Inelastic Response ◽  
Ship Model Test ◽  
Full Picture ◽  
Deformation Stress ◽  
The Impact

The dynamic behavior of a fully clamped rectangular plate impacted by a rigid knife-edge is studied in this paper. Based on the variational finite difference method, a numerical model of dynamic inelastic response of plates impacted by a rigid knife-edge indentor is being developed, which includes the influence of finite transverse displacements, axial restraints, bending moments, material elasticity and strain hardening. The struck plate and rigid striker were coupled in the numerical simulation, with the deformation, strain, stress and impact force as outputs of the calculation. Numerical results were given on a small-scale ship model test, which provides a full picture of the response of the clamped rectangular plate under dynamic load. It provides information on the impact force, deformation, stress and strain everywhere in the plate. Such data could not be obtained experimentally or by simple plastic formulations.

scholarly journals Experimental Investigation on the Impact Dynamics of Saturated Granular Flows on Rigid Barriers

2021 ◽  
Vol 27 (1) ◽  
pp. 127-138
Author(s):  
Nicoletta Sanvitale ◽  
Elisabeth Bowman ◽  
Miguel Angel Cabrera
Keyword(s):  
Particle Size ◽  
High Speed ◽  
Impact Load ◽  
Granular Flows ◽  
Normal Pressure ◽  
Impact Behavior ◽  
Small Scale ◽  
Rigid Barrier ◽  
Fluid Saturation ◽  
The Impact

ABSTRACT Debris flows involve the high-speed downslope motion of rocks, soil, and water. Their high flow velocity and high potential for impact loading make them one of the most hazardous types of gravitational mass flows. This study focused on the roles of particle size grading and degree of fluid saturation on impact behavior of fluid-saturated granular flows on a model rigid barrier in a small-scale flume. The use of a transparent debris-flow model and plane laser-induced fluorescence allowed the motion of particles and fluid within the medium to be examined and tracked using image processing. In this study, experiments were conducted on flows consisting of two uniform and one well-graded particle size gradings at three different fluid contents. The evolution of the velocity profiles, impact load, bed normal pressure, and fluid pore pressure for the different flows were measured and analyzed in order to gain a quantitative comparison of their behavior before, during, and after impact.

scholarly journals Land Use and Land Cover Changes and Their Effect on the Flow Regime in the Upstream Dong Nai River Basin, Vietnam

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1206 ◽  
Author(s):  
Nguyen Truong ◽  
Hong Nguyen ◽  
Akihiko Kondoh
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Flow Regime ◽  
River Basin ◽  
Vegetation Index ◽  
Secondary Forest ◽  
Spatial Scales ◽  
Small Scale ◽  
Land Cover Changes ◽  
The Impact

The upstream Dong Nai River Basin is located in the country’s key economic development region and its water resources are a key component of sustainable regional development. The objective of this study was to assess the impact of land use and land cover changes (LULCC) on the flow regime in this tropical forest basin using a flow–duration curve analysis that has been widely used in Japan. This study combined two different temporal and spatial scales of satellite data, Landsat and Global Inventory Modeling, and Mapping Studies (GIMMS) normalized difference vegetation index (NDVI) to analyze LUCC. Results from the land cover classification of five Landsat images between 1973 and 2014 indicated that the forest area decreased significantly in the period of 1994 to 2005 due to population growth, leading to land conversion for agriculture. Furthermore, secular changes in the annual GIMMS-NDVI data revealed that land cover changes occurred from 1996 and a large amount of forest was lost in 1999; however, due to the rapid regrowth of secondary forest of tropical forests and the development of the crop, the vegetation recovered shortly afterwards in 2000 before decreasing again after 2004. Following large-scale deforestation, the total discharge, maximum flow, and the plentiful, ordinary, low, and small-scale runoff increased sharply and decreased thereafter because of vegetation regrowth.

scholarly journals Large Scale Physical Modelling Study of a Flexible Barrier under the Impact of Granular Flows

2018 ◽  
Author(s):  
Dao-Yuan Tan ◽  
Jian-Hua Yin ◽  
Wei-Qiang Feng ◽  
Jie-Qiong Qin ◽  
Zhuo-Hui Zhu
Keyword(s):  
Debris Flows ◽  
Large Scale ◽  
Impact Force ◽  
Granular Flows ◽  
Physical Modelling ◽  
Flexible Barrier ◽  
Impact Forces ◽  
Flexible Barriers ◽  
Open Question ◽  
The Impact

Abstract. Flexible barriers are being increasingly applied to mitigate the danger of debris flows. However, how barriers can be better designed to withstand the impact loads of debris flows is still an open question in natural hazard engineering. Here we report an improved large-scale physical modelling device and the results of two consecutive large-scale granular flow tests using this device to study how flexible barriers react under impact from granular flows. In the study, the impact force directly on the flexible barrier and the impact force transferred to the supporting structures are measured, calculated and compared. Based on the comparison, the impact loading attenuated by the flexible barrier is quantified. The hydro-dynamic and hydro-static approaches are also validated using the calculated impact forces.

scholarly journals Large-scale physical modelling study of a flexible barrier under the impact of granular flows

2018 ◽  
Vol 18 (10) ◽  
pp. 2625-2640 ◽  
Author(s):  
Dao-Yuan Tan ◽  
Jian-Hua Yin ◽  
Wei-Qiang Feng ◽  
Jie-Qiong Qin ◽  
Zhuo-Hui Zhu
Keyword(s):  
Debris Flows ◽  
Large Scale ◽  
Impact Force ◽  
Granular Flows ◽  
Physical Modelling ◽  
Flexible Barrier ◽  
Static Approach ◽  
Flexible Barriers ◽  
Open Question ◽  
The Impact

Abstract. Flexible barriers are being increasingly applied to mitigate the danger of debris flows. However, how barriers can be better designed to withstand the impact loads of debris flows is still an open question in natural hazard engineering. Here we report an improved large-scale physical modelling device and the results of two consecutive large-scale granular flow tests using this device to study how flexible barriers react under the impact of granular flows. In the study, the impact force directly on the flexible barrier and the impact force transferred to the supporting structures are measured, calculated, and compared. Based on the comparison, the impact loading attenuated by the flexible barrier is quantified. The hydro-dynamic approaches with different dynamic coefficients and the hydro-static approach are validated using the measured impact forces.

scholarly journals Dry Granular Flows Impacts on Rigid Obstacles: DEM Evaluation of a Design Formula for the Impact Force

2016 ◽  
Vol 158 ◽  
pp. 290-295 ◽  
Author(s):  
Francesco Calvetti ◽  
Claudio di Prisco ◽  
Emmanouil Vairaktaris
Keyword(s):  
Impact Force ◽  
Granular Flows ◽  
Design Formula ◽  
The Impact

Impact Dynamics of Multi-Link Robots with Link and Joint Flexibility

2012 ◽  
Vol 226-228 ◽  
pp. 685-692 ◽  
Author(s):  
Zhen Jie Qian ◽  
Ding Guo Zhang
Keyword(s):  
Impact Force ◽  
Mathematic Model ◽  
Dynamics Simulation ◽  
Impact Dynamics ◽  
Flexible Link ◽  
Transformation Matrices ◽  
Rotary Joint ◽  
Manipulator Arm ◽  
Stretching Deformation ◽  
The Impact

The dynamic analysis of a flexible-link-joint robot colliding with its environments is presented in this paper. Kinematics of both rotary-joint motion and link deformation is described by 4×4 homogenous transformation matrices. Both the stretching deformation, bending deformation and the torsional deformation of the flexible links are considered. Furthermore, the flexibility and the mass of the joint are considered too. The concept of impact force potential energy is introduced, so that the generalized forces due to the impact force can be computed easily. The Lagrange dynamic equations are used to establish the complete mathematic model of the system with impact. Dynamics simulation of a spatial flexible-link-joint manipulator arm is given as an example to validate the algorithm presented in this paper. And the numerical results indicate that the flexibility of the link and joint have distinguished influence on the impact dynamics of the flexible robots.

Drop Impact Dynamics: Impact Force and Stress Distributions

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Xiang Cheng ◽  
Ting-Pi Sun ◽  
Leonardo Gordillo
Keyword(s):  
High Speed ◽  
Impact Force ◽  
Drop Impact ◽  
Impact Dynamics ◽  
Annual Review ◽  
Publication Date ◽  
High Speed Photography ◽  
Stress Distributions ◽  
Wide Range ◽  
The Impact

Dynamic variables of drop impact such as force, drag, pressure, and stress distributions are key to understanding a wide range of natural and industrial processes. While the study of drop impact kinematics has been in constant progress for decades thanks to high-speed photography and computational fluid dynamics, research on drop impact dynamics has only peaked in the last 10 years. Here, we review how recent coordinated efforts of experiments, simulations, and theories have led to new insights on drop impact dynamics. Particularly, we consider the temporal evolution of the impact force in the early- and late-impact regimes, as well as spatiotemporal features of the pressure and shear-stress distributions on solid surfaces. We also discuss other factors, including the presence of water layers, air cushioning, and nonspherical drop geometry, and briefly review granular impact cratering by liquid drops as an example demonstrating the distinct consequences of the stress distributions of drop impact. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals PREDICTION OF DYNAMIC AND QUASI-STATIC IMPACTS ON VERTICAL SEA WALLS CAUSED BY AN OVERTOPPED BORE

2018 ◽  
pp. 28
Author(s):  
Maximilian Streicher ◽  
Andreas Kortenhaus ◽  
Vincent Gruwez ◽  
Bas Hofland ◽  
Xuexue Chen ◽  
...  
Keyword(s):  
Prediction Accuracy ◽  
Large Scale ◽  
Impact Force ◽  
Vertical Wall ◽  
Impact Behavior ◽  
Small Scale ◽  
Run Up ◽  
The Individual ◽  
Two Peaks ◽  
The Impact

This study comprises a detailed description of the individual overtopped bore impact processes against a vertical wall, situated on top of a dike. A twin peak force impact signal shape was observed with two distinct peaks during every impact. The two peaks were assigned consecutively to the dynamic components (thickness and velocity) or hydrostatic components (run-up of water at the wall) of the impacting bore. The two peaks were termed dynamic F1 and quasi-static F2 impact respectively. Based on available literature semi-empirical equations to describe either the dynamic F1 or quasi-static F2 impact force were investigated and the prediction accuracy evaluated using impact force data from large-scale experiments. The prediction accuracy of the dynamic F1 impacts was very low. The prediction accuracy of the quasi-static impact F2 was increased based on fitting the hydrostatic theory to the maximum run-up measurement at the wall. Based on these findings 80% of the maximum run-up height was effectively contributing to the maximum quasi-static force F2 on the wall. The results coincided well with previous small-scale studies (Chen et al. 2012). After deconstructing the process chain preceding an impact, using the physically most meaningful parameters to predict the impact force, evaluating on a range of existing approaches, and observing the scattered prediction results, it was concluded that the impact behavior is highly stochastic and statistical analysis would be more beneficial.

Sign in / Sign up

Export Citation Format

Share Document