Jang-l You

Characteristics of wind velocity and temperature change near an escarpment-shaped road embankment

Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature) due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small.

Analysis of Air Current Flow around Noise Barrier on Expressways Using the PIV Technique

Urbanization has resulted in the extension of road networks and development of belt ways due to the expansion of cities and overpopulation. With the expansion of cities, resident population started to live nearby roads and is experiencing issues like spreading of air pollutants and noises generated on roads. In general, such issues are prevented by installing noise barrier and windproof walls on roadsides, which have great impact on reduction of noises and air pollutants. Previous studies about the effects of noise barrier and windproof walls on movement of pollutants were mostly conducted as partial field experiments and numerical experiments using computational fluid dynamics (CFD). Therefore, there is lack of studies on movement of wind and its effects. The purpose of this study is to examine form of actual wind based on noise barrier and the effects of wind on residents through particle image velocimetry (PIV).

A Study on the Wind Velocity Measuring According to the Opening Shapes Materials of High-rise Building Using CFD

Recently, diverse BIWP(Building-Integrated Wind Power) generation systems for application to buildings have been attempted, but studies on the effects of wind power generators in the upper regions of high-rise buildings are lacking. In this study, CFD analyses were conducted on the changes in the shapes and crosssectional areas of openings in the upper regions of buildings for the installation of wind power generators. Among the shapes of openings, circles showed the highest wind velocity, followed by squares and rectangles. In addition, with regard to the changes in wind angles, the maximum wind velocity value appeared when the wind angle was 30°, and the wind velocity rapidly decreased when the wind angle was 45° or larger.

LQG Control of Along-Wind Response of a Tall Building with an ATMD

Modern tall buildings use lighter construction materials that have high strength and less stiffness and are more flexible. Although this results in the improvement of structural safety, excessive wind-induced excitations could lead to occupant discomfort. The optimal control law of a linear quadratic Gaussian (LQG) controller with an active tuned mass damper (ATMD) is used for reducing the along-wind response of a tall building. ATMD consists of a second mass with optimum parameters for tuning frequency and damping ratio of the tuned mass damper (TMD), under the stationary random load, was used. A fluctuating along-wind load, acting on a tall building, was treated as a stationary Gaussian white noise and was simulated numerically, in the time domain, using the along-wind load spectra proposed by G. Solari in 1993. Using this simulated wind load, it was possible to calculate the along-wind responses of a tall building (with and without the ATMD), using an LQG controller. Comparing the RMS (root mean square) response revealed that the numerically simulated along-wind responses, without ATMD, are a good approximation to the closed form response, and that the reduced responses with ATMD and LQG controller were estimated by varying the values of control design parameters.

Characteristics of Wind Pressure Distributions Acting on Solar Collector Plate

This paper attempted to bridge this gap by identifying the number of flat-plate solar collectors. The characteristics of wind pressure coefficients acting on flat-plate solar collectors which are most widely used were investigated for various wind direction. Findings from this study found that the location where the maximum wind pressure coefficient occurred in the solar collector was the edge of the collector. Regarding the characteristics according to the number of collectors, the paper found that downward wind pressure coefficient of the lower edge of the collector was higher than the upward wind pressure coefficient of the upper edge of the collector in the basic module (1 piece). However, as the number of collectors increases, the upward wind pressure coefficient of the upper edge become higher than the downward wind pressure coefficient of the lower edge. Finally yet important, it was found that the location of the maximum wind pressure coefficient was changed according to the number of solar collectors.

Characteristic of Wind Pressure Distribution on the Roof of Hyperbolic Paraboloid Spatial Structures

There can be diverse causes in the destruction of a large space structure by strong wind such as characteristics of construction materials and changes in internal and external wind pressure of the structure. To evaluate the wind pressure of roof against the large space structure, wind pressure experiment is performed. However, in this wind pressure experiment, peak internal pressure coefficient is set according to the opening of the roof in Korea wind code. In this article, it was tried to identify the change of internal pressure coefficient and the characteristics of wind pressure coefficient acting on the roof by two kinds of opening on the side of the structure with Hyperbolic Paraboloid Spatial Structures roof. When analyzing internal pressure coefficient according to roof shape, it was found that minimum (52%) and maximum (30%~80%) overestimation was made comparing to partial opening type proposed in the current wind load. It is judged that evaluation according to the opening rate of the structure should be made to evaluate the internal pressure coefficient according to load.