Strong Wind Velocity Research Articles

Fire smoke dispersion inside and outside of a warehouse building in moderate and strong wind conditions

A moderate-sized (8 MW) fire was modelled in a warehouse located in an urban area with diverse architecture, in wind conditions. The investigation includes the effects of neighbouring architecture on the wind field, and in consequence on the smoke control performance and the smoke dispersion in the near-field of the building. Overall, 25 CFD simulations were performed with ANSYS Fluent CFD code, for wind velocities of 5 m/s (moderate), 10 m/s (strong) at 12 wind angles each (0°–330°, 30° increment), and at 0 m/s for reference. The building smoke venting system's performance was affected by the wind, reaching 74%–114% and 78%–158% of the reference mass flow at the moderate and strong wind velocities, respectively. Surprisingly, in multiple cases the exhaust flow rate of ventilators was increased, rather than hindered by the wind. We attribute this to the arrangement of inlets and outlets on façades and the resulting pressure difference between the wall and roof openings. The smoke plume was highly dependent on the wind angle, and the type of architecture up- and downwind of the fire. Significant urban canyon effects and large vortices forming behind tall buildings were observed, leading to smoke accumulation in a large distance from the fire.

Strength assessment of rice hills from different planting distance by loading simulation

Plant spacing arrangement might benefit hill strength from the impact of strong wind velocity during extreme weather situations. Here, a loading test to evaluate rice hill strength was performed on Ciherang variety grown in square and double row spacing 2:1. The research was conducted at Cilubang village, Dramaga, Bogor, West Java, Indonesia from March to May 2017. Weight holding capacity was evaluated in 85 days after transplanting on four levels of hill height, i.e., 80 cm, 60 cm, 40 cm, and 20 cm above soil level with three-time replication. The results showed that double-spaced hills had 66.0 % ± 3.1 % stronger than those of square spacing at all height measurement. To lodge a hill into 20 cm to 40 cm from soil level, it required 346.7 g to 741.7 g in square spacing, and 555.2 g to 1149.2 g in double row spacing. Stronger hills in double row spacing seemed to correlate with a higher number of tiller and hills architecture; it requires further study in the role of both factors on the hill strength improvement. The present study recommends applying double row spacing to improve rice hill strength especially at a time with a high chance of lodging by strong wind incident.

Numerical Investigation on Collision of Pollution Particles on Outdoor Insulators

Accumulation of pollution particles on outdoor insulators is the premise of pollution flashover accidents in power systems. In this paper, according to the actual operating polymer insulators, the wind velocity, the concentration of pollution particles, the diameter of pollution particles, and the hanging angle of insulator were considered to investigate the accumulation characteristic of pollution particles by using FLUENT software. The pressure nephogram of polymer insulator, the velocity vector of air flow field, movement trajectory of pollution particles, and collision rate were obtained. It is found that the pressure of the insulator surface on the windward side is bigger than that on the leeward side, and the pressure difference increases with increasing the wind velocity. As the increase in particle diameter, the collision rate between pollution particles and insulator surface shows the increasing tendency. When the diameter of pollution particles is small, the easier the particles follow the airflow to bypass the insulator surface without colliding with it. However, due to the influence of gravity force and inertia, the collision rate of pollution particles increases significantly with the increase in particle diameter. Under the strong wind velocity, the air swirls are generated on the leeward side of the insulator surface, causing the collision rate of the pollution particles increases slowly with the increase in the wind velocity. While the concentration of pollution particle increases, the collision number between insulator surface and pollution particles shows the increasing tendency at different wind velocity. When the particle diameter is in range of 1 to 8 μm, with increasing the hanging angle of “V”type insulator from 0° to 60°, the collision rate of pollution particles shows the increasing tendency. When the particle diameter is 9 to 50 μm, the collision rate of particles shows the increasing tendency when the insulator angle is lower than 30°, but shows the decreasing tendency from 30°to 60°. As the humidity increases, the water vapor in the air prevents the movement of pollution particles, resulting in a decrease in the collision rate. With increasing the pollution particles diameter, the influence of air humidity on the collision rate of pollution particles is gradually weakened.

LES of wind environments in urban residential areas based on an inflow turbulence generating approach

Wind environment in urban residential areas is an important index to consider when evaluating the living environment. However, due to the complexity of the flow field in residential areas, it is difficult to specify the correct inflow boundary conditions in the large eddy simulation (LES). In this paper, the weighted amplitude wave superposition (WAWS) is adopted to simulate the fluctuating velocity data, which satisfies the desired target wind field. The fluctuating velocity data are given to the inlet boundary of the LES by developing an UDF script, which is implemented into the FLUENT. Then, two numerical models - the empty numerical wind tunnel model and the numerical wind tunnel model with spires and roughness elements are established based on the wind tunnel experiment to verify the present method. Finally, the turbulence generation approach presented in this paper is used to carry out a numerical simulation on the wind environment in an urban residential area in Lisbon. The computational results are compared with the wind tunnel experimental data, showing that the numerical results in the LES have a good agreement with the experimental results, and the simulated flow field with the inlet fluctuations can generate a reasonable turbulent wind field. It also shows that strong wind velocities and turbulent kinetic energy occur at the passageways, which may affect the comfort of people in the residential neighborhood, and the small wind velocities and vortexes appear at the leeward corners of buildings, which may affect the spreading of the pollutants.

Aeolian processes and landforms in the sub-Antarctic: preliminary observations from Marion Island

Sub-Antarctic Marion Island has a hyperoceanic climate, with cold and wet conditions and consistently strong wind velocities throughout the year. Recent observations recognized the increasing role of aeolian processes as a geomorphic agent, and this paper presents the first data for transport by aeolian processes on a sub-Antarctic island. Data were collected through an intensive and high-resolution measurement campaign at three study sites using Big Spring Number Eight sediment traps and surface sediment samplers in conjunction with an array of climatic and soil logger sensors. Observed aeolian landforms are megaripples, and the data suggest that aeolian processes are also modifying solifluction landforms. The sediment traps and sediment samplers collected wind-blown scoria at all three study sites, and the annual (horizontal) aeolian sediment flux extrapolated from this preliminary data is estimated at 0.36–3.85 kg cm −2 y −1 . Importantly, plant material of various species was trapped during the study that suggests the efficiency of wind for the dispersal of plants in this sub-Antarctic environment may be underestimated. This paper advocates long-term monitoring of aeolian processes and that the link between aeolian processes and synoptic climate must be established. Furthermore, wind as a means to disperse genetic material on Marion Island should be investigated. Keywords: Marion Island; climate change; wind; erosion; dispersal. (Published: 23 November 2015) Citation: Polar Research 2015, 34 , 26365, http://dx.doi.org/10.3402/polar.v34.26365

Influence of meteorological conditions on trans-Pacific transport of Asian dust during spring season

Synoptic-scale meteorological features controlling the trans-Pacific transport (TPT) of Asian dust (AD) and its temporal and spatial distributions were examined in the regions between East Asia and North America, especially over the North Pacific Ocean during a dust episode in April 2001. These analyses were performed based on the meteorological maps, aerosol index (AI), aerosol optical depth (AOD), PM 10 measurements, and model studies (e.g., dust concentrations, geopotential heights, horizontal winds, and potential temperature). The dominant meteorological conditions affecting the TPT of AD (TPTAD) were found to be associated with the two synoptic features: (1) behavior of the strong westerlies along the trough path connected to surface cyclones in high latitudes and (2) the acceleration of westerlies merged with the airflows traveled along the conveyor belt (CB) zone over the North Pacific Ocean. The merged strong westerlies that developed from the CB (a strong wind velocity ( ⩾ 25 m s - 1 ) and the strong gradient of potential temperature ( ∼ 15 K )) played a significant role in the TPTAD. The TPTAD simulation showed agreement in the patterns and the concentration levels of modeled dust with those of the observations. Further evidences for the TPTAD were AI of ∼ 2 , AOD range of ⩽ 0.7 , and an increase of PM 10 concentrations (e.g., exceeding 80 μ g m - 3 ) in most of the counties of California during the dusty days.

Characteristics of water-soluble components of atmospheric aerosols in Yokohama and Mt. Oyama, Japan from 1990 to 2001

Abstract We continuously collected aerosol samples of PM7 from 1990 to 1997 and of PM10–2 and PM2 from 1998 to 2001 and measured their water-soluble components of pH, conductivity, major ions, dissolved organic carbon (DOC) and total mass (TM) in an urban site, Yokohama (35°28′N, 139°38′E) and the mountainside (680 m asl) of Mt. Oyama (35°28′N, 139°46′E, 1252 m asl), Japan, to contrast the aerosol composition between an urban site and a mountain site. In Yokohama, annual mean TM concentration decreased gradually for over 10 years with the decrease of NH4+, Mg2+, Cl−, and SO42− concentrations, and TM concentrations were the highest in winter and the lowest in summer. At Mt. Oyama, there was no significant change in the duration, and TM concentrations were the highest from late spring to early summer, although the seasonal variation was smaller. Equivalent concentration ratio of Cl− to Na+ at Mt. Oyama was lower than that in Yokohama, because Cl loss which occurred was larger for the aerosol collected at Mt. Oyama remote from the sea rather than Yokohama. The conversion ratio of sulfur to sulfate was calculated and the ratio was not affected strongly by the variation of Ox concentration at both sites and was high at Mt. Oyama in summer. NH4+, NO3−, SO42−, and DOC concentrations were higher under weak wind velocity than those under strong wind velocity regardless of the wind direction in both the sites.

In situ measurement of strong wind velocity spectra and wind characteristics at Keelung coastal area of Taiwan

In this study, we report the in situ measurement results of the strong wind turbulence statistics and wind velocity spectra at the Keelung coastal region of Taiwan. Strong winds induced by Babs typhoon on Oct. 25–27, 1998 were measured with an ultrasonic anemometer. The in situ measurement data included three components of the wind velocity and temperature. The probability density functions for the three components of the wind velocity fluctuations and the temperature fluctuation are shown to be close to the Gaussian distributions. The turbulence intensity and integral length scales of the strong wind are calculated. The observed longitudinal wind spectrum is found to be in agreement with the Von Karman's spectrum and the wind spectrum equation of Eurocode 1. Observational results of the lateral and the vertical wind spectra are approximately close to the predictions of the isotropic turbulence spectra equations.

Regression analysis of local wind properties with local topographic factors

Abstract To improve the accuracy of estimation of local strong wind, new local topographic parameters were introduced in the multiple regression analysis. New azimuthal topographic factors were defined independently of particular radius of fan-shaped area for the estimation of usual topographic factors. In addition to them, some micro-scale local terrain factors were defined from scenery pictures of 16-azimuths around the site. The azimuthal strong wind velocity at a construction site was evaluated through the two-step estimation, in which the representative wind speed at a site was estimated by first regression analysis with the usual topographic factors and second regression analysis with newly defined micro-scale factors was followed to estimate the azimuthal wind speed fluctuation. It was shown that the new topographic factors defined here played an important role in all regression analyses.

Variation of Aerodynamical Characteristics of a Barley Field with Growth

The data of wind and temperature profiles in the low-level air layers over the barley field were used to study the magnitudes of the profile parameters (z0, d, V* and Cd) and their variations with wind velocity and the growth conditions of the crop plants. The profile measurements were made on a 1.5ha field of the barley during the period from November 1964 to June 1965. All wind profile parameter computations are based on the data of ten-minute mean wind velocity profiles. The results obtained are summarized as follows:1. The zero plane displacement (d) increases with the plant height but decreases inversely with the wind velocity. An exponential function of the plant height approximates the variation of d. The value of exponent decreases with wind velocity.2. The roughness parameter (z0) decreases slightly with the wind velocity in the early stages of plant growth, but it increases inversely with the wind velocity in the later stages of the growth. Under the conditions that h is larger than 5cm, z0 is found to be proportional to hl. The exponent varies also from 0.75 at weak wind velocity to 1.35 at at strong wind velocity.3. Surface drag coefficient (Cd) varies with the wind velocity and the plant height. The coefficient is proportional to a power of the plant height in the same manner as z0 (see Fig. 5). The variation of friction velocity (V*) with both the wind velocity and the plant growth is expressed approximately byV*=0.4/0.74+Fu1501.02+0.29F.