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1. chinaXiv:202104.00091 [pdf]

Optimization designs of artificial facilities in deserts based on computational simulation

DUN,Hongchao; HUANG,Ning; ZHANG,Jie
Subjects: Geosciences >> Geography

Sediment transport of sand particles by wind is one of the main processes leading to desertification in arid regions, which severely impairs the ability of mankind to produce and live by drifting sand into settlements. Optimization designs of artificial facilities have lately attracted extensive interest for human settlement systems in deserts because of their acceptable protection effect, convenience of implementation, and low material cost. However, the complexity of a settlement system poses challenges concerning finding suitable materials, artificial facilities, and optimization designs for sand deposition protection. In an effort to overcome these challenges, we propose a settlement system built with brick, solar panel, and building arrays to meet the basic needs of human settlements in arid regions while preventing wind-sand disasters. The wind flow and movement characteristics of sand particles in the brick, panel, and building arrays were calculated using computational fluid dynamics and discrete phase model. The performance of three types of arrays in wind-sand flow in terms of decreasing the wind velocity and sand-particle invasion distance was evaluated. The results show that the wind velocity near the surface and the sand invasion distance were significantly decreased in the space between the brick arrays through properly selected vertical size and interspaces, indicating that the brick arrays have an impressive sand fixing and blocking performance; their effective protection distance was 3–4 m. The building arrays increased the near-surface wind velocity among buildings, resulting in less deposition of sand particles. The solar panel arrays were similar to the building arrays in most cases, but the deposition of sand particles on solar panels exerted a negative effect on energy utilization efficiency. Therefore, taking the optimal configuration of the settlement system into consideration, this study concludes that (1) brick arrays, which were proven effective in preventing sand particles, must be arranged in an upwind area; (2) solar panel arrays could accelerate the wind flow, so they are best to be arranged at the place where sand particles deposited easily; and (3) building arrays present a better arrangement in downwind areas.

submitted time 2021-04-22 From cooperative journals:《Journal of Arid Land》 Hits2165Downloads245 Comment 0

2. chinaXiv:202005.00088 [pdf]

Effect of the W-beam central guardrails on wind-blown sand deposition on desert expressways in sandy regions

WANG Cui; LI Shengyu; LEI Jiaqiang; LI Zhinong; CHEN Jie
Subjects: Biology >> Botany >> Applied botany

Many desert expressways are affected by the deposition of the wind-blown sand, which might block the movement of vehicles or cause accidents. W-beam central guardrails, which are used to improve the safety of desert expressways, are thought to influence the deposition of the wind-blown sand, but this has yet not to be studied adequately. To address this issue, we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow, the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions. The subgrade model is 3.5 cm high and 80.0 cm wide, with a bank slope ratio of 1:3. The W-beam central guardrails model is 3.7 cm high, which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column. The wind velocity was measured by using pitot-static tubes placed at nine different heights (1, 2, 3, 5, 7, 10, 15, 30 and 50 cm) above the floor of the chamber. The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler, which was sectioned into 20 intervals. In addition, we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016, by using a customized 78-cm-high gradient sand sampler for the sand flux structure test. Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade, and the wind velocity on the leeward side weakens significantly. The W-beam central guardrails decrease the leeward wind velocity, whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails. The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails. At 0.0H and 0.5H (where H=3.5 cm, which is the height of the subgrade), the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails, and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface. The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height. The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points, which is consistent with the position of the minimum wind velocity in the wind tunnel test. The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.

submitted time 2020-05-31 From cooperative journals:《Journal of Arid Land》 Hits13875Downloads1319 Comment 0

3. chinaXiv:202004.00052 [pdf]

Effect of the W-beam central guardrails on wind-blown sand deposition on desert expressways in sandy regions

WANG Cui; LI Shengyu; LEI Jiaqiang; LI Zhinong; CHEN Jie
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Many desert expressways are affected by the deposition of the wind-blown sand, which might block the movement of vehicles or cause accidents. W-beam central guardrails, which are used to improve the safety of desert expressways, are thought to influence the deposition of the wind-blown sand, but this has yet not to be studied adequately. To address this issue, we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow, the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions. The subgrade model is 3.5 cm high and 80.0 cm wide, with a bank slope ratio of 1:3. The W-beam central guardrails model is 3.7 cm high, which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column. The wind velocity was measured by using pitot-static tubes placed at nine different heights (1, 2, 3, 5, 7, 10, 15, 30 and 50 cm) above the floor of the chamber. The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler, which was sectioned into 20 intervals. In addition, we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016, by using a customized 78-cm-high gradient sand sampler for the sand flux structure test. Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade, and the wind velocity on the leeward side weakens significantly. The W-beam central guardrails decrease the leeward wind velocity, whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails. The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails. At 0.0H and 0.5H (where H=3.5 cm, which is the height of the subgrade), the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails, and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface. The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height. The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points, which is consistent with the position of the minimum wind velocity in the wind tunnel test. The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.

submitted time 2020-04-23 From cooperative journals:《Journal of Arid Land》 Hits1244Downloads684 Comment 0

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