Papers by Keyword: Wind Tunnel Test

Abstract: As 70% of the terrain of Korea consists of mountains, it is required to incorporate embankments, bridges and tunnels, etc. into road construction plans. The change in wind flow caused by the construction of embankment, in particular, has led to the increase of wind flow damage. In this study, a research was conducted on the method to facilitate wind flow, changed by the road embankment using culvert. There were a total of 52 points, of which 26 points were in front of the road embankment and 26 points in the back of the road embankment. When the number of two culverts were the same, the wind speed around the culvert was greater by more than 5% ~ 40% in the culvert size 6.0m x 4.5m than in the culver size 3.0m x 2.5m. The findings of the experiment indicates that the reduced wind speed of the wind flow entering and passing through the inlet of culvert can mitigate the congestion of wind flow that would otherwise be caused by the installation of the culvert.

Abstract: This paper introduces an automatic shutdown system for model protection during the flutter test in high speed wind tunnels. This automatic shutdown system can be used to determine any unsafe condition through model flutter signals before triggering shutdown of wind tunnels, solving problems of delayed response and mistakes happen during manual measurement of subcritical state of model flutter. The reliability and effectiveness of this system have been proved good via wind tunnel tests, hence the possibility of damage to the model caused by flutter during the flutter test of high speed wind tunnels can be decreased.

Abstract: To study aerodynamic interference of twin-deck sections under vortex-induced vibration (VIV), a series of wind tunnel tests are implemented. Horizontal interval ratio (D/B) is taken into consideration a factor influencing VIV behavior, and the results are compared with single section. Surface pressure distribution of the twin sections are acquired by synchronous pressure measurements when the sections are under vertical and torsional VIV. Proper orthogonal decomposition (POD) is employed to reconstruct the randomly fluctuating wind pressure field. It identifies the vertical and torsional vibration frequency of model and energy proportion of eigenmodes. VIV behavior of twin-deck sections is different from single section, and it changes with different D/B. In general, the position, where D/B=1, is unfavorable to VIV behavior of twin-deck sections. The aerodynamic interference does not always amplify or restrain the amplitude of VIV. Several lower modes can reconstruct fluctuating pressure field to the accuracy meeting the requirement of engineering.

Abstract: The main research methods to predict and research wind loads on buildings at home and abroad include wind tunnel tests, field measurement and numerical simulation. However, the wind tunnel tests and field measurement require big funds, long cycle and complicated measurement. Moreover, numerical simulation technology is quite mature. In this paper, based on fluid dynamics software CFD and criteria Reynolds k-ε turbulence model, wind field of the village flat roof with parapet is studied using the numerical simulation technology. Furthermore, the wind pressure data in different wind angles are processed and analyzed. The results show that wind angle has a significant impact on the wind pressure and its distribution. When the wind angle is 0 °, the air pressure-fluctuation in each node of the roof is small, and the pressure coefficient is steady between -1.50 and -2.00. When the wind angle is 45 °, the air pressure fluctuation in each node of the roof is large, and the pressure coefficient fluctuates between -0.8 and -3.0. When the wind angle is 90 °, the wind pressure-fluctuation in each node of the roof is equal to the fluctuation between 0 ° and 45 °wind direction angle, and the wind pressure coefficient fluctuates between -0.7 and -1.7. When incoming flow is along the asymmetric axis, the wind pressure-fluctuation is large, and the wind pressure is greater than that in the large negative pressure zone which is along the symmetry axis, which can bring serious damage on the roof.

Abstract: In evaluating wind load effects on large-scale structures, correlations in the frequency domain (i.e., coherences) and power spectra of fluctuating wind speed should be evaluated in advance. Most existing formulas for coherence are expressed as exponential functions based on field measurement data for ease of mathematical treatment. However, these simple mathematical expressions have many limitations. In the present study, after examining the existing coherence formulas, a semi-theoretical formula was proposed, and the corresponding along-wind force power spectrum of a tall building with a square cross-section was numerically calculated. A comparison showed that both the coherence and along-wind power spectrum were in good agreement with those of actual wind tunnel data.

Abstract: Aeroelastic wind tunnel tests were conducted on conventional and tapered super-tall buildings to investigate the effect of the taper on the aeroelastic behavior for various wind directions and normalized velocities, with a focus on the maximum tip displacement. The natural frequencies and damping ratios were adjusted by means of the spring stiffness and magnetic field at the bottom of the test models. The displacements at the bottom of the test models were measured and transformed to tip displacements. The results showed that the taper suppressed the maximum tip displacement in both the X and Y directions, although the suppression was greater in the Y direction, especially for small wind directions. Moreover, the variations of the maximum tip displacement in the X direction with the wind direction and normalized velocity were small.

Abstract: This paper adopts self-designed wing model to conduct flutter test on subsonic and transonic, and obtains flutter characteristic of the model, and the test results are used for calibration and verification of flutter procedures. The sub-critical extrapolation is used to obtain the flutter sub-critical parameters and the direct observation method is used to obtain comparison of results. Error of results obtained by the two approaches does not exceed 5%, and validates reliability of the sub-critical prediction approach in continuous adjusted dynamic pressure flutter test.

Abstract: Videogrammetric measurement is a research focus for the organizations of wind tunnel test because of its no special requirements on the test model, its key techniques for the vibration environment of the high speed wind tunnel are introduced by this paper, such as the solution of exterior parameters with big-angle large overlap, the algorithm of image processing for extracting marked point, the method of camera calibration and wave-front distortion field measurement. The great requirements and application prospects of videogrammetry in wind tunnel fine testing have been demonstrated by several practice experiments, including to measure test model’s angle of attack, dynamic deformations and wave-front distortion field in high speed wind tunnels whose test section size is 2 meters.

Abstract: The responses of tall buildings under wind loads in hilly terrain are remarkably different from that in flat terrain. Wind load codes can’t work efficiently or directly to calculate the wind-induced vibration of tall buildings in hilly terrain. Utilizing some wind tunnel test results of wind field in hilly terrain and pressures on tall buildings, the access to response of tall buildings on hilly terrain were provided. Some effects from hill characteristics to building responses were discussed.

Abstract: In this paper, 2 high-rise building models with ladder and cascade irregularities of elevation were tested in a wind tunnel respectively to measure the mean and fluctuating wind pressure distributions. The mean and RMS (root-mean-square) coefficients of the drag, lift and torsion moment on the measuring layer were obtained from the wind pressures. In the direction which the buildings were positive in the wind, the variation of these above mentioned coefficients with height and the power spectrum densities of the fluctuating wind loads on sudden changed positions were analyzed in detail. Compared with the elevation regular tall building, the wind load characteristics of irregular ones were more complicated.