Unloading Characteristics of Sand-drift in Wind-shallow Areas along Railway and the Effect of Sand Removal by Force of Wind

Abstract

Wind-shield walls decrease the velocity of wind-drift sand flow in transit. This results in sand accumulating in the wind-shadow zone of both windshield wall and track line, causing severe sand sediment hazard. This study reveals the characteristics of sand accumulation and the laws of wind-blown sand removal in the wind-shadow areas of three different types of windshield walls, utilizing three-dimensional numerical simulations and wind tunnel experiments and on-site sand sediment tests. The results revealed the formation of apparent vortex and acceleration zones on the leeward side of solid windshield walls. For uniform openings, the vortex area moved back and narrowed. When bottom-opening windshield walls were adopted, the track-supporting layer at the step became a conflux acceleration zone, forming a low velocity vortex zone near the track line. At high wind speeds, windshield walls with bottom-openings achieved improved sand dredging. Considering hydrodynamic mechanisms, the flow field structure on the leeward side of different types of windshield structures is a result of convergence and diffusion of fluids caused by an obstacle. This convergence and diffusion effect of air fluid is more apparent at high wind velocities, but not obvious at low wind velocities.

M/v Ever Given: Legal Assessment of the Causes and Consequences of the Accident

“…Consequently, the density of such a suspension is greater than the density of the usual flow generated in the wind tunnel when determining the aerodynamic characteristics of the body. Thus, the presence of sandy suspension in the air can impair the vessel's manoeuvrability [17] and lead to a loss of control even at a safe wind speed of 9 m/s, as identified in one of the SCA's main arguments [12], [21].…”

“…However, to rely on this exemption, the carrier must prove in any case that the marine hazard that caused loss/damage was unpredictable, so knowledge of the weather is a crucial factor in determining whether the carrier can rely on the exemption or is negligent, For weather conditions. Usually, the latter had to deny him entry to the canal [7], [21].…”

Generalized diffusion and random search processes

“…The CTRW model [14,36,37] was applied, for example, to infiltration of anomalously diffusing particles from one material to another through a biased interface [38], and recently in the long-term prediction of 137 Cs concentration in the lakes after the Fukushima Daiichi Nuclear Power Plant accident [39], where the contamination particle ( 137 Cs) follows a long-tailed waiting time between jumps. Additionally to the ground and underground water pollution, such CTRW models could apply to model propagation of sandstorm particles, including pathogens or microbes carried by the sandstorm [40][41][42]. The sandstorm particles fly over a long distance before they arrive at the particular area and stay around for some time while the next flight takes place.…”

Wind-Tunnel Studies on Sand Sedimentation Around Wind-Break Walls of Lanxin High-Speed Railway II and Its Prevention

“…The mechanism of sand sedimentation on the leeward sides of wind-break walls has recently been given serious attention. Cheng analyzed the characteristics of sand accumulation of three different types of wind-break walls by three-dimensional numerical simulations and wind-tunnel experiments and found that the wind-break wall with bottom-openings achieved improved sand dredging at high wind speeds [16]. Huang explored the characteristics of wind-blown sand flow around the wind-break wall and the causes of sand accumulation by setting up a turbulent flow-sand particle-terrain coupling model using the Lagrangian particle-tracing model and found that sand particles will be blown up and rolled back to the subgrade under the effect of vertical wind velocity and reflux [15].…”