Simulated Natural Wind Research Articles

Surrogate atmospheric dust particles generated from dune soils in laboratory: Comparison with field measurement

Desert dust strongly influences the climate and the environment by altering the radiation budget, participating in atmospheric chemical reactions, and engaging the biogeochemical cycle. Studying its impacts requires knowledge of the physical and chemical properties of the original particles from the source origin. Unfortunately, the field collection of atmospheric samples in the desert is impractical. Fine surface soil is thus considered an alternative material from which to obtain the information applicable to dust particles from the desert soil. In this study, a laboratory system was set up to generate dust particles with simulated natural wind erosion processes from surface soils or directly from desert surfaces. Surface soils and field dust were simultaneously collected during a local blowing dust event. The comparison between the laboratory-generated dust and the field dust showed a consistent trend in particle size distribution and chemical composition. The chemical compositions were found to have explainable differences with the Certified Reference Materials for Asian dust (CJ-2). The laboratory-generated dust particles with the system could be applied as surrogates for soil-emitted dust in desert areas.

Study on simulated natural wind based on spectral analysis

A dynamic thermal environment meeting human health requirements can be created with natural wind simulated by artificial means. Simulating natural wind can provide an innovative air-conditioning mode that reduces the energy consumption of air-conditioning systems and avoids the body-resistance decrease and body-temperature regulation mechanism failure that limit the traditional steady air-conditioning mode. In this paper, new methods for simulating natural wind are presented in which the controllable fluctuation of mechanical wind is improved to make its characteristics more similar to those of natural wind. Experiments carried out to verify the effectiveness of these mechanical-wind methods are reported. A self-operated air supply device improving the fluctuation of the air supply is proposed, which can increase the value of the characteristic parameter β (the negative slope of the double-logarithmic power spectrum curve) to 1.2 when the wind speed is greater than 1 m/s. With a second proposed device based on the gas-washing process, this value can reach 1.4 when the wind speed is greater than 0.5 m/s. In summary, this paper provides simple solutions for simulating natural wind.

Fatigue Life Prediction for Semi-Closed Noise Barrier of High-Speed Railway under Wind Load

The fatigue state of the semi-closed noise barrier directly affects driving safety, and replacement after damage leads to train delays and increased operating costs. It is more eco-friendly and sustainable to predict the fatigue life of noise barriers to reinforce the structure in time. However, previous life prediction methods provide a limited reference in the design stage. In this study, a novel fatigue life prediction method for noise barriers was proposed. The computational fluid dynamics and finite element model of the semi-closed noise barrier were established and subjected to simulated natural wind and train aerodynamic impulse wind loads to calculate the stress time-history on the noise barrier. Based on the rain flow counting method and Miner linear cumulative fatigue damage theory, the fatigue life of noise barriers in three Chinese cities was predicted. The results show that the fatigue life of the noise barrier is closely related to the wind conditions and train operation modes. Targeted reinforcement for noise barriers in different fatigue states can save materials and reduce maintenance workload. Moreover, the influence of wind load on the noise barrier was summarized, and engineering suggestions on prolonging the fatigue life of noise barriers were put forward.

Experimental Study of the Aerodynamics of Sail in Natural Wind

Abstract In order to evaluate the impacts of a motor vessel after installing wind sails, the aerodynamics of the sail should be accurately calculated. However most of the research on sails are based on stable wind instead of natural wind which is changing horizontally and vertically. In this paper wind tunnel tests are carried out based on stable wind field and simulated natural wind field, the results shown that there are 16–44% decrease in natural wind in terms of lifting coefficient and 11–42% decrease for drag coefficient. This would provide a valuable reference to the effectiveness evaluation of the impact of sails for sail assisted ships.

Application of dynamic airflows in buildings and its effects on perceived thermal comfort

In this paper we explore the performance of a newly developed air conditioner which can produce different airflow modes such as dynamically changed simulated natural wind (SNW) and constant mechanical wind (CMW). Climate chamber experiments were conducted to study the demand for air movement and to compare effects of SNW and CMW on human subjects’ thermal comfort perception in warm environment. The results indicate that it was possible for subjects to remain comfortable at 28℃ and 30℃ with a suitable air velocity range of 0.4–0.6 and 0.7–0.9 m/s, respectively. Compared with CMW, SNW produced stronger cooling effect and induced better perceived thermal comfort voting from human subjects. Over 60% of these subjects preferred SNW to CMW. These experimental findings would serve as a reference for the design of more energy saving space conditioning systems in warm climates.

Experimental study of improved HAWT performance in simulated natural wind by an active controlled multi-fan wind tunnel

The effects of turbulent intensity and vortex scale of simulated natural wind on performance of a horizontal axis wind turbine (HAWT) are mainly investigated in this paper. In particular, the unsteadiness and turbulence of wind in Japan are stronger than ones in Europe and North America in general. Hence, Japanese engineers should take account of the velocity unsteadiness of natural wind at installed open-air location to design a higher performance wind turbine. Using the originally designed five wind turbines on the basis of NACA and MEL blades, the dependencies of the wind frequency and vortex scale of the simulated natural wind are presented. As the results, the power coefficient of the newly designed MEL3-type rotor in the simulated natural wind is 130% larger than one in steady wind.

0506 能動制御乱流風洞を用いた速度変動模擬自然風における水平軸風車の性能評価

0506 能動制御乱流風洞を用いた速度変動模擬自然風における水平軸風車の性能評価

Influence of Walls and Ceiling on a Wind Flow in BLWT Tunnel

This paper deals with determination of the parameters of simulated boundary layer in newly built Boundary Layer Wind Tunnel (BLWT). Short description of tunnel, measuring devices and possibilities of using of tunnel are mentioned here. All measurements, which were necessary for basic analysis of simulated natural wind, are shortly mentioned. The main part of this paper is devoted to additional measurements, which were necessary for detection of influences of boundary effects in part of the cross-section of tunnel where the calibration of Hot-wire anemometer is usually done. These boundary effects evoke deceleration of the wind velocity in given area. Description of additional measurements and obtained results are presented at the end of this paper.

Effects of airflow on thermal comfort before sleep onset in a warm and humid climate

Fans are widely used in south-east of China to increase heat loss day and night in summer time. However, all-night rotating speed control system, which can produce sleeping-friendly airflow, has not been proposed under rigorous human experimental results. Sleeping model, nowadays, prevails on the market, are figured out by testing, to be a variant of the simulated natural wind model which is a beta product in the laboratory, thus the so-called sleeping fans are likely to cause rheumatic pan or even temporary paralysis after all-night using. In this study, customs of using fans during the sleep by Chinese people from different regions and ages are collected through an internet survey distributed in the summer time. The results of the survey show the necessity of sleeping-friendly airflow, customary fan displacement and the preference to the fan type, which partly become the fundamental settings of the human experiment. The human experiment in this study is a preliminary exploration of the airflow preference preceding sleep initiation, in which subjects wearing short pyjamas, supine on a bed covered by rattan mat with a towel blanket under the following conditions: (1) air temperature(Ta) 30?, relative humidity(RH) 60%, and air velocity(V) 0.6m/s, 1.0m/s, 1.5m/s, 2.0m/s. Common protocol of subjective evaluation on the effect of airflow is obtained for all subjects. TSV declines with the increasing of air velocity, and arrives 0.5 when air velocity is around 0.8m/s, 0.2m/s lower than that under upright condition. Nearly all subjects prefer the airflow with a constant air velocity to the simulated natural wind with a changeable air velocity. The draft is mainly from too high air velocity and immobile airflow direction.

Influence of dynamic environment with different airflows on human performance

The influence of constant mechanical wind (CMW) and simulated natural wind (SNW) on human comfort and performance was investigated in a climate chamber. Eighteen subjects (twelve males and six females) were recruited. Four conditions with airflow were designed, including 28 °C with CMW and SNW, 30 °C with CMW and SNW. Two steady-state environments of 26 °C and 28 °C without airflow were also arranged for comparison. Performance was evaluated using three simulated office tasks – memory typing, addition and pattern matching. Subjects were required to finish questionnaires to evaluate their thermal sensation, thermal comfort, satisfaction of environment, workload and working motivation. The results suggested that both airflows would increase comfort in warm environments and the improvement effect was better at 30 °C than at 28 °C. SNW performed better for comfort and working motivation at 30 °C while CMW was better at 28 °C. The performance showed no difference under different environments except for few conditions in the addition task. The influence of CMW and SNW showed no significant influence on human performance.

A dynamic air supply device used to produce simulated natural wind in an indoor environment

Natural ventilation is the most pleasant and suitable ventilation mode. Many researchers have claimed that they have produced simulated natural wind (SNW) using artificial devices. However, the characteristics of these kinds of SNW have been shown, through spectral analysis, to be clearly different from true natural wind (TNW). In this study, a dynamic air supply device based on direct-current (DC) motor control was designed to produce SNW, and the spectral characteristics of the airflow produced by this device were very close to those of TNW. To verify the application potential of this SNW, an experiment on thermal sensation and thermal comfort with regard to the SNW was conducted in both a climate chamber and a real office. Twenty-one subjects were exposed to five conditions: a constant neutral environment at 26 °C; a warm environment at 28 and 30 °C with constant mechanical wind (CMW), and a warm environment at 28 and 30 °C with SNW. In addition, twelve subjects used the device during work in a real office. The data of their thermal sensations was analyzed. The results suggested that the SNW was more effective in improving thermal comfort than the CMW in the warm environments. It was demonstrated that using SNW in a warm environment could result in almost the same thermal comfort as in a constant neutral environment.

Random Lock-In Intervals for Tubular Structural Elements Subject to Simulated Natural Wind

This paper reports on wind tunnel experiments with an elastically suspended circular cylinder vibrating under the excitation of natural wind of high turbulence degree. The natural wind turbulence was simulated by superposing the low frequency part of the natural wind turbulence on the background high frequency turbulence of the wind tunnel flow. This was done by controlling the propeller rotation speed according to an artificially generated low frequency speed sample function drawn from a suitable random process model. The experiment provided statistical data on the intermittent random occurrence and size of strong lock-in vibrations in resonance with the vortex shedding excitation. The purpose of the experiment was to obtain data to support the formulation of a sufficiently detailed stochastic model to allow computer simulation of reasonably realistic fatigue damage accumulation at “hot spots” of tubular structural elements subject to the natural wind. The engineering relevance of the investigation is supported by comparing it with the unrealistic highly conservative rules of wind-induced fatigue commonly given in codes of practice. The stochastic lock-in model as well as the related fatigue calculation procedure is reported in the paper.

Building downwash of plumes and plume interactions

This paper presents a number of wind tunnel measurements of building induced downwash effects on the plume in a neutrally stable boundary layer. Vertical and horizontal profiles of mass concentrations of the exhausts from stacks on a rectangular model building were measured downwind of the buoyant source in the near wake. These experiments were conducted in a simulated natural wind over open country terrain for various freestream wind speeds with different stack and building configurations. Significant downwash effects from the building below the stack were observed in all tested configurations. In this preliminary study, only mean concentrations were evaluated and are presented in non-dimensional form.

A new boundary-layer wind tunnel at the Danish Maritime Institute

The paper describes a new boundary-layer wind tunnel at the Danish Maritime Institute in Lyngby. The wind tunnel is of the open-circuit type and is integrated into a building raised for the purpose. The design was constrained by the need to provide a simulation of the atmospheric boundary layer (without thermal stratification) and alternatively a uniform flow without excessive turbulence. The wind tunnel has a working section of principal dimensions: length 20.8 m, width 2.6 m and height 1.8 m (adjustable from 1.8 to 2.3 m). The maximum wind speed in the working section when empty is about 26 m s −1. Data acquisition, analysis and instrumentation in relation to the new wind tunnel are discussed and, finally, an example of a simulated natural wind is presented.

A versatile compact wind tunnel for industrial aerodynamics

A wind tunnel of compact closed circuit configuration designed specifically for industrial aerodynamics is described and its performance discussed. It has a working section 2 m wide × 1 m high × 6.5 m long with a maximum windspeed of 18 m s −1 under typical operating conditions, and a secondary high speed working section 0.5 m wide × 1 m high × 1.75 m long. A feature of the tunnel is a flow processing region upstream of the main working section, where apparatus to simulate various conditions of the atmosphere can be easily and quickly installed and interchanged. The uniformity of velocity and level of turbulence in the main working section are compromised somewhat by the compact design, but are good enough for many industrial aerodynamic problems where simulated natural wind conditions are required rather than an aerodynamically smooth flow. The tunnel is powered by a 60-kW hydraulic drive system, employs contra-rotating fans and a multi-cell rapid diffuser. It is mainly of very simple design and construction. The current cost in Britain (late 1970) would be of the order of £8500, assuming all construction work were contracted out.