scholarly journals Wind Speed Response of Sap Flow in Five Subtropical Trees Based on Wind Tunnel Experiments

2013 ◽  
pp. 160-171 ◽  
Author(s):  
Sophie Laplace ◽  
Tomonori Kume ◽  
Chia-Ren Chu ◽  
Hikaru Komatsu
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Sap Flow ◽  
Wind Tunnel Experiments ◽  
Speed Response

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.

scholarly journals Effect of Angle of Attack on Airfoil NACA 0012 Performance

2020 ◽  
Vol 5 (1) ◽  
pp. 35-40
Author(s):  
Ali Akbar
Keyword(s):  
Fluid Flow ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Lift Force ◽  
Angle Of Attack ◽  
Lower Surface ◽  
Wind Tunnel Experiments ◽  
A Value ◽  
The Difference ◽  
Naca 0012

Airfoil is an aerodynamic form intended to produce a lift force with the smallest drag force. When an airfoil is passed through a fluid flow that causes interaction between the air flow and the surface, variations in velocity and pressure will occur along the top and bottom surfaces of the airfoil, as well as the front and back of the airfoil. The difference in pressure between the upper and lower surface of the airfoil is what causes the resultant force in the direction perpendicular to the direction of fluid flow, this force is called the lift force (lift). In this experiment NACA 0012 airfoil experiments have been carried out using simple wind tunnel. Experiments were conducted with the aim to determine the effect of the angle of attack on the performance of the NACA 0012 airfoil which then analyzed the lift force of the NACA 0012 airfoil. The variation of the angle of attack used was 0 °, 3 °, 6 °, 9 °, 12 °, and 15 ° and used wind speed of 21.5 m / s. The greatest lift force is obtained at an angle of attack of 9 ° with a value of 0.981 while the largest lifting coefficient with a value of 0.106. The greater the angle of attack the greater the airfoil lift force, but for symmetrical airfoil stall at an angle that is too large

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.

scholarly journals Development of saltation layer of drifting snow

2004 ◽  
Vol 38 ◽  
pp. 35-38 ◽  
Author(s):  
Takeshi Sato ◽  
Kenji Kosugi ◽  
Atsushi Sato
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Snow Cover ◽  
Friction Velocity ◽  
Transport Rate ◽  
Strong Wind ◽  
Wind Tunnel Experiments ◽  
Drifting Snow ◽  
Starting Point

AbstractThe saltation length of aeolian snow particles and a new parameter, the ejection factor, which expresses the degree of erosion due to drifting snow, were obtained as functions of friction velocity by means of wind-tunnel experiments for semi-hard snow cover. The saturated-snowdrift transport rate was also obtained experimentally as a function of friction velocity. Based on these characteristics and the parameter, the development of the saltation layer of drifting snow along the fetch was simulated under various conditions such as snow hardness, wind speed and snowfall intensity. The main results are as follows. The developing distance denoting the distance required for the saltation layer to attain saturation, X sat, is determined by saltation length, ejection factor and saturated-snowdrift transport rate, all of which depend on wind speed. It is also affected by the magnitude of snowdrift transport rate at the starting point and by the intensity of snowfall if it exists. The dependence of Xsat on wind speed is not simple in the case of semi-hard snow cover: Xsat increases with wind speed under weak to moderate wind conditions and then decreases under moderate to strong wind conditions. It is sensitive to snow hardness: it is about one order longer on hard snow cover than on semi-hard snow cover. Snowfall reduces not only the value of Xsat but also its dependence on snow hardness.

Accurate determination of reference wind speed and reference static pressure in wind tunnel tests

2019 ◽  
Vol 23 (3) ◽  
pp. 578-583
Author(s):  
YC He ◽  
JCK Cheung ◽  
QS Li ◽  
JY Fu
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Measurement Method ◽  
Static Pressure ◽  
Accurate Determination ◽  
Indirect Measurement ◽  
Measurement Methods ◽  
Wind Tunnel Experiments

The reference wind speed and reference static pressure are two key parameters for determining the testing results of wind tunnel experiments. Traditionally, the values of these parameters can be determined using direct measurement methods. However, such methods may suffer from less accuracy and inconvenience of operations. This article documents an indirect measurement method which, compared to the traditional methods, has the merits of higher accuracy and greater operational convenience. Examples are presented to demonstrate the main procedures of the method and typical findings by using the method in a boundary layer wind tunnel.

scholarly journals Design of a Wind Sensor Based on Cylinder Diametrical Pressure Differences for Boundary Layer Meteorological Observation

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 1511
Author(s):  
Zhan Zhao ◽  
Yichen Pan ◽  
Rongjian Zhao ◽  
Lidong Du ◽  
Zhen Fang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Pressure Difference ◽  
Pressure Sensors ◽  
Differential Pressure ◽  
Two Dimensional ◽  
Relative Speed ◽  
Meteorological Observation ◽  
Wind Tunnel Experiments

Wind speed and direction are important parameters in meteorological observation. Solid wind sensor has needed with small Quadcopter for boundary layer meteorological observation. In this paper the principle of a cylindrical two-dimensional wind sensor is reported by analyzing the data from wind tunnel experiments. A model is proposed to describe the distribution of the pressure difference across a diameter of a cylinder and the wind sensor is fabricated with MEMS differential pressure sensors. In wind tunnel tests in range of 1~40 m/s, the relative speed measuring errors and the direction measuring errors of the prototype are no more than ±(0.2 + 0.03 V) m/s and 5° respectively.

scholarly journals High Accuracy and Miniature 2-D Wind Sensor for Boundary Layer Meteorological Observation

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1194 ◽  
Author(s):  
Yichen Pan ◽  
Zhan Zhao ◽  
Rongjian Zhao ◽  
Zhen Fang ◽  
Hong Wu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Measurement Accuracy ◽  
Pressure Sensors ◽  
Micro Electro Mechanical System ◽  
High Accuracy ◽  
Relative Speed ◽  
Meteorological Observation ◽  
Wind Tunnel Experiments

Wind speed and direction are important parameters in meteorological observation. A solid wind sensor is needed with a small quadcopter for boundary layer meteorological observation. In this paper, the principle of a cylindrical two-dimensional wind sensor is reported and the data from wind tunnel experiments are analyzed. A model is proposed to describe the distribution of the pressure difference across a diameter of a cylinder, and the wind sensor is fabricated with MEMS (Micro-Electro-Mechanical System) differential pressure sensors. The wind sensor cylinder has a small size with a diameter of 30 mm and a height of 80 mm. In wind tunnel tests in the range of 1 to 40 m/s, the relative speed measuring errors and the direction measuring errors of the prototype are no more than ± (0.2 + 0.03 V) m/s (V is standard wind speed) and 5°, respectively. An inclination angle model is proposed to correct the influence of tilt angle on the quadcopter platform, the wind sensor can maintain the original wind speed and direction measurement accuracy within the 30° inclination range after compensation.

Planetary saltation: Should we care about cohesion?

2020 ◽  
Author(s):  
Francesco Comola ◽  
Thomas Pähtz ◽  
Orencio Duran
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Surface Sediments ◽  
Threshold Value ◽  
Small Range ◽  
Wind Tunnel Experiments ◽  
Ongoing Controversy ◽  
Formation And Evolution ◽  
Theoretical Evidence ◽  
Theoretical Conceptualization

<p>Sediment transport in saltation is an important driver of the morphodynamics of planetary sedimentary surfaces and particularly responsible for the formation and evolution of aeolian ripples and dunes. When estimating the incidence and persistence of saltation on extraterrestrial planetary bodies, geomorphologists usually ask by how much the atmospheric winds on such bodies exceed the threshold value required to initiate saltation, a question that is inherently linked to the cohesiveness of a body's surface sediments. For example, there is currently an ongoing controversy about the saltation initiation threshold on Saturn's moon Titan because of strongly varying estimations of the cohesiveness of Titan's soils. If the value of this threshold is outside a certain relatively small range, the currently leading explanation for an observed mismatch between Titan's dune orientation and the predominant atmospheric wind direction is thought to break down. Here we put up for discussion an alternative viewpoint on the importance of cohesion and saltation initiation. First, we briefly review experimental and theoretical evidence from the literature suggesting that, in the field (in contrast to wind tunnel experiments), saltation is almost always easily initiated, which means that one mainly needs to understands whether saltation can be sustained once initiated. Second, we present results from DEM-based numerical simulations suggesting that saturated saltation, in particular the smallest wind speed at which it can be sustained (i.e., the cessation threshold), is almost unaffected by cohesion. Third, we show a simple theoretical conceptualization that explains these numerical results and, when implemented in an analytical model, captures existing cessation threshold and saltation transport rate measurements. Finally, we show that the predictions of this model are consistent with several direct and indirect observations associated with extraterrestrial saltation, including the orientation of Titan's dunes.</p>

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