Influence Of Wind Flow Research Articles

Research on Collision Warning Method for Ship-Bridge Based on Safety Potential Field

In order to ensure the safety of navigation in a bridge area, and based on the theory of the safety potential field, a method of ship safety assessment and early warning in an inland river bridge area is proposed. Firstly, the risk elements associated with ship collisions in a bridge area are classified. Secondly, these risks are quantified using the potential energy field, the boundary potential field and the behavioural field, and then the ship state under the influence of wind flow, predicted by the Kalman filter, is quantified using the kinetic energy field. Then, the above four potential energy fields are merged to obtain a superposition field, and the magnitude of the instantaneous risk in the bridge area is obtained based on its magnitude. Finally, the change of field strength values under different moments is used for early warning. The results of the simulation of a ship passing through the piers of the Baijusi Bridge show that the model can effectively quantify the risk of a ship–bridge collision in the inland bridge area and provide real-time warning of the risk of a ship–bridge collision in the bridge area, which is of great significance for improving the safety of the inland bridge area.

Influence of Wind Flows on Surface O3 Variation over a Coastal Province in Southeast China

Surface ozone (O3) is influenced not only by anthropogenic emissions but also by meteorological factors, with wind direction being one of the most overlooked factors. Here, we combine the observational data of both O3 and wind flow to compare the variation in surface O3 with wind direction between coastal and inland regions of Fujian, a province in the southeast coast of China with complicated topography. We further conduct a numerical simulation using a global chemical transport model, GEOS-Chem, to interpret the observational results, explore the linkages between these O3 variations and wind flows, and identify the dominant processes for the occurrence of high O3 that varies with wind flows. The results from the observations over 2015–2021 suggest that, over coastal regions, surface O3 concentrations show a strong dependence on wind flow changes. On average, during the daytime, when southeasterly winds prevail, the mean of O3 concentrations reaches 83.5 μg/m3, which is 5.0 μg/m3 higher than its baseline values (the mean O3 concentrations), while the northwesterly winds tend to reduce surface O3 by 6.4 μg/m3. The positive O3 anomalies with southeasterly wind are higher in the autumn and summer than in the spring and winter. During the nighttime, the onshore northeasterly winds are associated with enhanced O3 levels, likely due to the airmass containing less NO2, alleviating the titration effects. Over inland regions, however, surface O3 variations are less sensitive to wind flow changes. The GEOS-Chem simulations show that the prevailing southeasterly and southwesterly winds lead to the positive anomaly of chemical reactions of O3 over coastal regions, suggesting enhanced photochemical production rates. Furthermore, southeasterly winds also aid in transporting more O3 from the outer regions into the coastal regions of Fujian, which jointly results in elevated surface O3 when southeasterly winds dominates. When affected by wind flows in different directions, the chemical reaction and transport in the inland regions do not exhibit significant differences regarding their impact on O3. This could be one of the reasons for the difference in O3 distribution between coastal and inland regions. This study could help to deepen our understanding of O3 pollution and aid in providing an effective warning of high-O3 episodes.

Development of an anti-vibration aircraft model support system with magnetorheological annular squeeze dampers for wind tunnel

Sting support is an important equipment in wind tunnel test and is also vulnerable to resonance under the influence of wind flow, which will reduce the accuracy of test data and even pose a hazard to the wind tunnel. To address the vibration problem, an innovative magnetorheological sting support (MRSS) was proposed in this paper. Specifically, the vibration reduction mechanism was explained by using a combination of Euler-Bernoulli beam and Kelvin-Voigt element. Furthermore, the relationship between the stiffness and damping of the magnetorheological damper (MRD) and the natural frequency (NF) and damping ratio (DR) characteristics of the MRSS was illustrated. To provide controllable damping and stiffness for the support system, an MRD with annular squeeze mode was designed, taking into account various factors such as low influence on wind flow, sting shape, and magnetic circuit requirements, and was also optimized by considering target magnetic field and low power consumption as the objectives. Tests on the manufactured MRD demonstrate the effectiveness of the structure design and optimization. Also, the response time characteristic satisfies the system vibration control. Subsequently, the controllability and superior fail-safe property of MRSS were verified through laboratory and wind tunnel tests. Finally, an on–off control logic was developed, and real-time vibration control tests were conducted in various impulse excitation, the resonance peak was significant attenuated by 27.1 dB. Additionally, the resonance peak was attenuated by 17.6 dB in the passive state. The experimental results showed that the MRSS was able to suppress the vibration with efficiency and reliability.

Numerical analysis of dust pollution evolution law caused by ascensional/descensional ventilation in fully mechanized coal mining face based on DPM-DEM model

To understand the problem of differences in the dust migration law of ascensional and descensional ventilation, this study numerically simulates the dust migration law under the condition of ascensional and descensional ventilation, and proposes corresponding automatic spray control schemes. The results show that under the influence of wind flow, the migration distance of dust under ascensional ventilation was longer than that under descensional ventilation at the same time, and the distance difference of dust migration between ascensional and descensional ventilation also increased with the evolution of time. Among them, the distance differences at 10 s, 25 s, 50 s and 75 s were 2 m, 7 m, 9 m and 14 m respectively. The lift of the ascensional wind hindered dust deposition, which caused the dust at 0–15 m on the downwind side of the shearer to seriously affect the breathing belt, with an average dust concentration of 1683.3 mg/m³ . The thrust of the descensional wind caused the roof near the moving support to seriously affect the breathing belt, with an average dust concentration of 1435.1 mg/m³ .

Heat loss investigation of 125kWth solar LFR pilot plant with parabolic secondary evacuated receiver for performance improvement

Numerical investigation is carried out on the secondary reflector system of the pilot solar linear Fresnel reflector module of 154 m2 in Vallipuram, Tamil Nadu. Initially, optical investigation on the design of the Linear Fresnel Collector module and the secondary reflector system is carried out. The optimized flux thus obtained is applied as a boundary condition to the thermal loss analysis. Investigation of the total heat losses (convective, radiative and conductive) with three different boundary conditions namely, the constant flux, variable flux and non-uniform flux distribution is carried out. The heat loss study has been carried out when the absorber is under non-evacuated and evacuated state. The study has been carried out with the DNI ranging between 250 W/m2 and 1000 W/m2. Uncoated and selectively coated absorbers with the emissivity of 0.01–1 are analyzed. Comprehensive analysis on the influence of wind flow on the receiver system is carried out. The variation of wind velocity from the ground level is incorporated in the forced convection. Investigation on the effect of the wind speed (0 m/s–10 m/s) and the wind direction (0°–90°) on this second stage reflector system is analyzed. The deviation between the different flux boundary conditions is comprehensively analyzed under different DNI and wind conditions. The variable flux distribution shows less deviation of about 15% from the non-uniform flux distribution for the DNI of 1000 W/m2 and is found to be less than 5% for 500 W/m2 under evacuated conditions. To avoid the computational complications in applying non-uniform flux boundary conditions to the absorber for DNI greater than 500 W/m2, variable boundary flux condition can be applied as an equivalent flux condition by augmenting 15% non-uniform error percentage to the final heat loss value.

Response types and general stability conditions of linear aero-elastic system with two degrees-of-freedom

The unified linear variant of the general mathematical description of stability conditions for a girder with a bluff cross-section under the influence of wind flow is presented. A double degree-of-freedom model for the heave and pitch self-excited motion is used. The properties of the response located at the stability limits and the tendencies of the response in their vicinity are analyzed by means of the Routh–Hurwitz theorem. The respective stability conditions are depicted in the frequency plane delimited by the frequencies of two principal aero-elastic modes. Conditions for flutter onset and divergence are identified as special cases of the general theory. The results can be used as an explanation of several experimentally observed effects. The application of this method to real bridges is presented and compared with existing results from other approaches.

The influence of wind flows on thermal comfort in the Daechung of a traditional Korean house

Daechung, a semi-open space with wooden floor located between the front and backyards of traditional Korean residences, is well known as a cool space in summer due to cross-ventilation, but it has not yet been scientifically explained thoroughly. The purpose of this paper is to characterize the wind flow measured at a Daechung to interpret the effects of the wind characteristics on thermal comfort. We measured 10-Hz turbulence data at the Daechung and partitioned the wind vector into two directions (i.e. backyard to Daechung and front yard to Daechung). Interestingly, the wind from the cool backyard flowing through the Daechung was of less frequency and shorter duration but had higher velocity compared to wind from the opposite direction, which can provide thermal comfort to the dwellers. We suggest that the wind characteristics were determined by various aspects of the house's design, such as its location and the degree of enclosure in front and backyards. The results show that traditional Korean house made use of a natural ventilation system during the summer. The principles of this system could be helpful in constructing environmentally friendly and sustainable residences.