Variation in Grain-size Characteristics of Stimulated Shrubs As a Novel Sand-barrier in a Wind Tunnel Experiment

2021 ◽  
Author(s):  
Xia Pan ◽  
Zhenyi Wang ◽  
Yong Gao ◽  
Zhongjv Meng ◽  
Xiaohong Dang ◽  
...  
Keyword(s):  
Grain Size ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Speeds ◽  
Average Grain Size ◽  
Spatial Configurations ◽  
Desert Regions ◽  
Grain Size Parameters ◽  
Soil Grain Size ◽  
Arid And Semiarid

<p>Sand transport is the main manifestation of sand damage in the arid and semiarid desert regions globally. It is still a challenge for ecologists to stabilize mobile sandy and to change them into stable productive ecosystems. The establishment of stimulated shrubs is one of the most effective measures as a novel sand-barrier. Meanwhile, it has a beautiful visual effect in deserts. To better understand its role in the process of ecological restoration, we conducted a wind tunnel experiment to analyze the overall characteristics of soil grain-size variation of different spatial configurations with simulated shrubs in row spaces under different net wind speeds. The results present that the average grain-size content was dominated by medium sand and fine sand, and the total percentage was more than 90%. The average grain-size content for other soil grain-size was almost the same and the proportion was less than 10%. Moreover, the sand deposition of simulated shrubs with different spatial configurations increased with the improvement of wind speed. And the average sand deposition of spindle-shaped simulated shrubs in 17.5×17.5cm and broom-shaped simulated shrubs in 17.5×26.25cm under different wind speeds was the least. There was less variation of the soil grain-size parameters among different spatial configurations of stimulated shrubs, row spaces, and net wind speeds. The effects of row spaces on average grain-size parameters would be improved with the increase of wind speed. By calculating the “correct” characteristics of any specific shelter device, all of these findings suggest that the application of the simulated shrubs will be an important component to further extend ecological engineering projects in arid and semiarid desert regions.</p>

scholarly journals Variation in grain-size characteristics of simulated shrubs as a novel sand-barrier in a wind tunnel experiment

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110093
Author(s):  
Zhenyi Wang ◽  
Xia Pan ◽  
Limin Yuan ◽  
Yong Gao ◽  
Xiaohong Dang ◽  
...  
Keyword(s):  
Grain Size ◽  
Wind Tunnel ◽  
Semiarid Regions ◽  
Wind Speeds ◽  
Average Grain Size ◽  
Spatial Configurations ◽  
Grain Size Parameters ◽  
Soil Grain Size ◽  
Arid And Semiarid ◽  
Sand Deposition

Sand transport is the main manifestation of sand damage in the arid and semiarid regions globally. It is a huge challenge to stabilize mobile sandy and change them into stable productive ecosystems. The establishment of simulated shrubs is one of the most effective measures to solve the above difficulties as a novel sand-barrier. To clarify simulated shrubs’ role in the process of ecological restoration. It will be greatly helpful to incorporate the shelter device proposed in the present work into landscape models for aeolian soil transport, to optimize the parameters associated with the sand-barrier characteristics for aeolian soil stabilization at the field scale. A series of wind tunnel experiments were conducted to analyze the variations of soil grain-size of simulated shrubs with different spatial configurations, row spaces, and net wind speeds. Further, the soil grain-size parameters were calculated by the classic method proposed by Folk and Ward to clarify the change of soil particles resulted from the blocking effects. The average grain-size content of simulated shrubs with different spatial configurations, row spaces, and net wind speeds was dominated by medium sand and fine sand, and the total percentage was more than 90%. Moreover, the sand deposition of simulated shrubs with different spatial configurations increased with the improvement of wind speeds. The average sand deposition of spindle-shaped simulated shrubs in 17.5 × 17.5 cm and broom-shaped simulated shrubs in 17.5 × 26.25 cm under different net wind speeds was the least. The effects of row spaces on average grain-size parameters increased with the improvement of net wind speeds. By calculating the correct characteristics of specific shelter devices proposed in the present work, all of these findings suggest that the application of simulated shrubs will be an important component to further extend ecological engineering projects in arid and semiarid regions.

Study on the Relation Between Side Ratios of Rectangular Cross Sections and Secondary Vortices at Trailing Edge in Motion-Induced Vortex Excitation

2017 ◽  
Author(s):  
Kazutoshi Matsuda ◽  
Kusuo Kato ◽  
Kouki Arise ◽  
Hajime Ishii
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Cross Sections ◽  
Leading Edge ◽  
Trailing Edge ◽  
Wind Speeds ◽  
Smoke Flow ◽  
Flow Visualizations ◽  
Institute Of Technology ◽  
Secondary Vortices

According to the results of conventional wind tunnel tests on rectangular cross sections with side ratios of B/D = 2–8 (B: along-wind length (m), D: cross-wind length (m)), motion-induced vortex excitation was confirmed. The generation of motion-induced vortex excitation is considered to be caused by the unification of separated vortices from the leading edge and secondary vortices at the trailing edge [1]. Spring-supported test for B/D = 1.18 was conducted in a closed circuit wind tunnel (cross section: 1.8 m high×0.9 m wide) at Kyushu Institute of Technology. Vibrations were confirmed in the neighborhoods of reduced wind speeds Vr = V/fD = 2 and Vr = 8 (V: wind speed (m/s), f: natural frequency (Hz)). Because the reduced wind speed in motion-induced vortex excitation is calculated as Vr = 1.67×B/D = 1.67×1.18 = 2.0 [1], vibrations around Vr = 2 were considered to be motion-induced vortex excitation. According to the smoke flow visualization result for B/D = 1.18 which was carried out by the authors, no secondary vortices at the trailing edge were formed, although separated vortices from the leading edge were formed at the time of oscillation at the onset wind speed of motion-induced vortex excitation, where aerodynamic vibrations considered to be motion-induced vortex excitation were confirmed. It was suggested that motion-induced vortex excitation might possibly occur in the range of low wind speeds, even in the case of side ratios where secondary vortices at trailing edge were not confirmed. In this study, smoke flow visualizations were performed for ratios of B/D = 0.5–2.0 in order to find out the relation between side ratios of rectangular cross sections and secondary vortices at trailing edge in motion-induced vortex excitation. The smoke flow visualizations around the model during oscillating condition were conducted in a small-sized wind tunnel at Kyushu Institute of Technology. Experimental Reynolds number was Re = VD/v = 1.6×103. For the forced-oscillating amplitude η, the non-dimensional double amplitudes were set as 2η/D = 0.02–0.15. Spring-supported tests were also carried out in order to obtain the response characteristics of the models.

Effect of Nozzle Angleson Spray Losses Reduction

2014 ◽  
Vol 564 ◽  
pp. 216-221
Author(s):  
Nasir S. Hassen ◽  
Nor Azwadi Che Sidik ◽  
Jamaluddin Md Sheriff
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Mean Value ◽  
The Other ◽  
Spray Drift ◽  
Spray Application ◽  
Application Process ◽  
Nozzle Height ◽  
Wind Speeds ◽  
Flat Fan Nozzle

Spray losses are the most important problem that is faced in the spray application process as result of spray drift to non target areas by the action of air flow.This paper investigated the spray drift for banding applicationusing even flat-fan nozzle TPEunder wind tunnel conditions.In addition, this paper also examined the effect of different spray fan angles 65°, 80° and 95° on spray drift particularly where there is need to make the nozzle operate at the optimum heights above the ground or plant level.In addition, three cross wind speeds 1, 2 and 3m/swere produced to determine the effect of wind speed on total spray drift.According to the results from this study, the nozzle anglehas a significant effect on the total spray drift. The nozzle angle 65° gave the highest drift reduction compared to the other nozzle angles. The maximum driftfor all nozzles was found at nozzle height of 60 cm. The minimum mean value of the drift was found at wind speed of 1 m/s. This study supports the use of nozzle angles of less than 95° on heights more than 0.5m and on wind speeds more than 1m/s as a means for minimizing spray drift.

scholarly journals Investigation of the Superposition Effect of Oil Vapor Leakage and Diffusion from External Floating-Roof Tanks Using CFD Numerical Simulations and Wind-Tunnel Experiments

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 299
Author(s):  
Jie Fang ◽  
Weiqiu Huang ◽  
Fengyu Huang ◽  
Lipei Fu ◽  
Gao Zhang
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Simulation Method ◽  
Vapor Concentration ◽  
Monitoring And Control ◽  
Wind Tunnel Experiments ◽  
Ambient Wind ◽  
Wind Speeds ◽  
High Concentrations ◽  
And Control

Based on computational fluid dynamics (CFD) and Realizable k-ε turbulence model, we established a numerical simulation method for wind and vapor-concentration fields of various external floating-roof tanks (EFRTs) (single, two, and four) and verified its feasibility using wind-tunnel experiments. Subsequently, we analysed superposition effects of wind speed and concentration fields for different types of EFRTs. The results show that high concentrations of vapor are found near the rim gap of the floating deck and above the floating deck surface. At different ambient wind speeds, interference between tanks is different. When the ambient wind speed is greater than 2 m/s, vapor concentration in leeward area of the rear tank is greater than that between two tanks, which makes it easy to reach explosion limit. It is suggested that more monitoring should be conducted near the bottom area of the rear tank and upper area on the left of the floating deck. Superposition in a downwind direction from the EFRTs becomes more obvious with an increase in the number of EFRTs; vapor superposition occurs behind two leeward tanks after leakage from four large EFRTs. Considering safety, environmental protection, and personnel health, appropriate measures should be taken at these positions for timely monitoring, and control.

Wind tunnel tests on the characteristics of wind fields over a simplified gorge

2016 ◽  
Vol 20 (10) ◽  
pp. 1599-1611 ◽  
Author(s):  
Peng Hu ◽  
Yongle Li ◽  
Yan Han ◽  
CS Cai ◽  
Guoji Xu
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Direction ◽  
Wind Field ◽  
Small Range ◽  
Wind Fields ◽  
Wind Speeds ◽  
Mean Wind Speed ◽  
Wind Characteristics ◽  
The Mean

Characteristics of wind fields over the gorge or valley terrains are becoming more and more important to the structural wind engineering. However, the studies on this topic are very limited. To obtain the fundamental characteristics information about the wind fields over a typical gorge terrain, a V-shaped simplified gorge, which was abstracted from some real deep-cutting gorges where long-span bridges usually straddle, was introduced in the present wind tunnel studies. Then, the wind characteristics including the mean wind speed, turbulence intensity, integral length scale, and the wind power spectrum over the simplified gorge were studied in a simulated atmospheric boundary layer. Furthermore, the effects of the oncoming wind field type and oncoming wind direction on these wind characteristics were also investigated. The results show that compared with the oncoming wind, the wind speeds at the gorge center become larger, but the turbulence intensities and the longitudinal integral length scales become smaller. Generally, the wind fields over the gorge terrain can be approximately divided into two layers, that is, the gorge inner layer and the gorge outer layer. The different oncoming wind field types have remarkable effects on the mean wind speed ratios near the ground. When the angle between the oncoming wind and the axis of the gorge is in a certain small range, such as smaller than 10°, the wind fields are very close to those associated with the wind direction of 0°. However, when the angle is in a larger range, such as larger than 20°, the wind fields in the gorge will significantly change. The research conclusions can provide some references for civil engineering practices regarding the characteristics of wind fields over the real gorge terrains.

scholarly journals Aerodynamic Characteristics Over Fine-Grained Gravel Surfaces in a Wind Tunnel

2021 ◽  
Vol 9 ◽  
Author(s):  
Jiaqi Liu ◽  
Reiji Kimura ◽  
Jing Wu
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Lower Layer ◽  
Aerodynamic Characteristics ◽  
Gobi Desert ◽  
Near Surface ◽  
Fine Grained ◽  
Wind Speeds ◽  
Speed Fluctuations

Gravels can protect soil from wind erosion, however, there is little known about the effects of fine-grained gravel on aerodynamic characteristics of the near-surface airflow. Drag coefficient, wind-speed gradient, and turbulent transfer coefficient over different coverages of gravel surfaces were investigated in a compact boundary-layer wind tunnel. The drag coefficient of the fine-grained gravel surface reached the maximum value at 15% coverage and then tended to stabilize at gravel coverage 20% and greater. At a height of 4 cm, near-surface airflow on gravel surfaces can be divided clearly into upper and lower sublayers, defined as the inertial and roughness sublayers, respectively. The coefficient of variation of wind speed over gravel surfaces in the roughness sublayer was 8.6 times that in the inertial sublayer, indicating a greater effect of gravel coverage on wind-speed fluctuations in the lower layer. At a height of 4 cm, wind-speed fluctuations under the observed wind speeds were independent of changes in gravel coverage. In addition, an energy-exchange region, where sand particles can absorb more energy from the surrounding airflow, was found between the roughness and inertial sublayers, enhancing the erosional state of wind-blown sand. This finding can be applied to evaluate the aerodynamic stability of the gravel surface in the Gobi Desert and provide a theoretical basis for elucidation of the vertical distributions of wind-blown sand flux.

scholarly journals Windbreak and airflow performance of different synthetic shrub designs based on wind tunnel experiments

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244213
Author(s):  
Xia Pan ◽  
Zhenyi Wang ◽  
Yong Gao ◽  
Zhengcai Zhang ◽  
Zhongjv Meng ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Erosion ◽  
Protective Effects ◽  
Wind Tunnel Experiments ◽  
Speed Reduction ◽  
Environmental Threats ◽  
Wind Speeds ◽  
Airflow Field ◽  
Reduction Effect

Wind erosion has gained increasing attention as one of the most serious global ecological and environmental threats. Windbreaks are effective at decreasing wind erosion by reducing wind speed to protect crops, livestock, and farmsteads, while providing wildlife habitats. Synthetic shrubs can act as novel windbreaks; however, there is limited knowledge on how their design affects wind speed. This study determined the protective effects (airflow field and sheltering efficiency) based on the design of synthetic shrubs in a wind tunnel. Broom-shaped synthetic shrubs weakened the wind speeds mainly at the middle and upper parts of the shrubs (5–14 cm), while for hemisphere-shaped shrubs this effect was greatest near their bases (below 4 cm) and least in the middle and upper parts (7–14 cm). Spindle-shaped synthetic shrubs provided the best reduction effect in wind range and strength. Moreover, the wind speed reduction ratio decreased with improved wind speeds and ranged from 26.25 cm (between the second and third rows) to 52.5 cm (after the third row). These results provide strong evidence that synthetic shrubs should be considered to decrease wind speed and prevent wind erosion.

CFD Application for the Characterization of Surface Pressures on Telescopes

2005 ◽  
Author(s):  
Balaji Kaushik ◽  
Richard D. Hale ◽  
Ray Taghavi
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Vertical Plane ◽  
Weighted Average ◽  
Operating Conditions ◽  
Average Technique ◽  
Wind Speeds ◽  
Reflective Surface ◽  
Critical Configuration ◽  
Common Parent

Aerodynamic trade studies in support of an interdisciplinary research program for large ground based telescopes are addressed. Numerous CFD (Computational Fluid Dynamics) trade studies were carried out to help identify the initial critical configuration of the telescope. The highest pressures induced on the reflective surface of the telescope mirror in the critical configuration were used in structural analysis. A module that correlated disparate discretizations in structural and fluid analyses through common parent geometry was developed. This module mapped surface pressures from the CFD discretization to the structural discretization using a weighted average technique. Experimental validation of the CFD results was carried out in the University of Kansas subsonic wind tunnel. The results from the CFD analysis and the wind tunnel experiments were in close agreement, with the maximum variation of pressures being 1%–8%. The preliminary telescope configuration that induced the highest pressure on the reflective surface of the primary mirror was identified as one inclined at 60° from the vertical plane and facing the wind directly. An “open-air” CFD model was developed that simulated the observatory shut-off operating conditions of 15 m/s wind speed and a fail-safe operating condition of 50 m/s wind speed. Critical local total gage pressures were 165 Pa and 1400 Pa at 15 and 50 m/s wind speeds respectively.

scholarly journals Structural Characteristics of Snow Drifts and Cornices

1985 ◽  
Vol 6 ◽  
pp. 287-288 ◽  
Author(s):  
Renji Naruse ◽  
Hiroshi Nishimura ◽  
Norikazu Maeno
Keyword(s):  
Grain Size ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Mass Balance ◽  
Structural Characteristics ◽  
Wind Tunnel Experiment ◽  
Surface Mass Balance ◽  
Field Observations ◽  
Surface Mass ◽  
Horizontal Step

Sorting effects of snow particles during deposition were studied in field observations of snow cornices and wind-tunnel experiment of snow drifts. Grain size, density and hardness were larger at the upper part (root) of a cornice than at the lower part (scarp). Experiments with the use of a horizontal step in a wind-tunnel revealed the importance of redistribution of snow particles on the formation of drifts: at wind speed of 5 m/s, about 40% of particles fallen onto the surface behind a 0.1-m high step were removed by erosion, rebound and creep. The surface mass balance controlling the growth and shape of a drift are briefly discussed.

scholarly journals Optimizing the Coupling of a Firebrand Generator to a Horizontal Wind Tunnel

2013 ◽  
Vol 726-731 ◽  
pp. 971-976
Author(s):  
Javad Hashempour ◽  
Ahmad Sharifian
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Test Section ◽  
Experimental Studies ◽  
Fire Spread ◽  
Horizontal Wind ◽  
Experimental Facility ◽  
Velocity Difference ◽  
Wind Speeds ◽  
Computational Work

Australia is considered as the most fire-prone country in the world. Spotting ignition by lofted firebrands is the main mechanism of fire spread. Many experimental studies have been conducted to evaluate the effect of the firebrand attacks on structures and to identify possible solutions. The experimental facility consists of a firebrand generator coupled to a wind tunnel. The wind speed in the firebrand generator is relatively low, in order to assure a quality continuous flow of glowing firebrands. On the contrary, the wind speed in the wind tunnel is high to duplicate actual firebrand attacks. Previous works show a highly turbulent region above the entrance of firebrands to the wind tunnel which is formed because of the velocity difference and penetration of firebrand entrance hose into the wind tunnel. The penetration is required to provide a uniform firebrand distribution along the height of the test section. In this computational work, the influence of the height of the entrance hose, its orientation respect to the tunnel and the distance between the coupling port and the test section are analyzed. The optimized results are presented and discussed for a variety of wind speeds within the wind tunnel and the firebrand generator.

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