• Wind and Structures
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• v.13 no.2
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• pp.127-144
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• 2010

Pressure measurements on static and autorotating flat plates have been recently reported by Lin et al. (2006), Holmes, et al. (2006), and Richards, et al. (2008), amongst others. In general, the variation of the normal force with respect to the angle of attack appears to stall in the mid attack angle range with a large scale separation in the wake. To date however, no surface pressures have been measured on auto-rotating plates that are typical of a certain class of debris. This paper presents the results of an experiment to measure the aerodynamic forces on a flat plate held stationary at different angles to the flow and allowing the plate to auto-rotate. The forces were determined through the measurement of differential pressures on either side of the plate with internally mounted pressure transducers and data logging systems. Results are presented for surface pressure distributions and overall integrated forces and moments on the plates in coefficient form. Computed static force coefficients show the stall effect at the mid range angle of attack and some variation for different Reynolds numbers. Normal forces determined from autorotational experiments are higher than the static values at most pitch angles over a cycle. The resulting moment coefficient does not compare well with current analytical formulations which suggest the existence of a flow mechanism that cannot be completely described through static tests.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.579-582
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• 2005

The sound measurement techniques in IEC 61400-11 are applied to field test and evaluation of noise emission from 1.5 MW wind turbine generator (WTG) at Yongdang-Lee and 650 kW WTG at Hangwon-Lee in Jeju Island. Apparent sound power level, wind speed dependence and third-octave band levels are evaluated for both of WTGs. 1.5 MW WTG at Yongdang is found to emit lower sound power than 660 kW one at Hangwon, which seems to be due to lower rotating speed of the rotor of WTG at Yongdang. Equivalent continuous sound pressure level s (ECSPL) of 650 kW WTG at Hangwon vary more widely with speed than those of 1.5 MW WTG at Yongdang. The reason for this is believed to be the fixed blade-rotating speed of WTG at Yongdang. One-third octave band analysis of the measured data show that the band components around 400-500 Hz are dominant for 1.5 MW WTG at Yongdang and those around 1K Hz are dominant for 660 kW WTG at Hangwon.

• International Journal of High-Rise Buildings
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• v.2 no.3
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• pp.229-244
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• 2013

Twenty six pressure models of high rise buildings with various cross-sections including twisted models were tested in a boundary layer wind tunnel. The cross-sections were triangular, square, pentagon, hexagon, octagon, dodecagon, circular, and clover. This study investigates variations in peak pressures, and effects of various cross-sections and twist angles on peak pressures. To study the effects of various configurations and twist angles on peak pressures in detail, maximum positive and minimum negative peak pressures at each measurement point of the building for all wind directions are presented and discussed. The results show that peak pressures greatly depend on building cross-section and twist angle.

• Journal of Sensor Science and Technology
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• v.21 no.1
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• pp.75-81
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• 2012

Optimizing the tapping time of a blast furnace is important to a stable operation and life extension. To optimize the tapping time of the blast furnace, the location of Hearth Liquid Level should be recognized. There are several ways to measure the hearth liquid level in the blast furnace, such as Electromotive Force(EMF) measurement, pressure measurement by putting in nitrogen probe and manometry with strain gauge. In this paper, it will be discussed using strain gauge among the three methods. Conventional strain gauge must be revised periodically. Since, internal pressure, temperature of internal refractory material and wind pressure have effect on the strain gauge. However, static pressure value is required to compensate. To solve these problems, this paper suggests finding relationship between Hearth Liquid Level and strain gauge output, adding digital filter in strain gauge. Using the proposed method, it was possible to estimate the hearth liquid level and determine the appropriate tapping time. Usefulness of the proposed method through simulations and experimental results are confirmed.

• Wind and Structures
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• v.26 no.6
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• pp.397-413
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• 2018

Excitation mechanism of interference effect between two tall buildings is investigated with wind tunnel experiments. Synchronized building surface pressure and flow field measurements by particle image velocimetry (PIV) are conducted to explore the relationship between the disturbed wind flow field and the consequent wind load modification for twin buildings in tandem. This reveals evident excitation mechanisms for the fluctuating across-wind loads on the buildings. For small distance (X/D < 3) between two buildings, the disturbed flow pattern of impaired vortex shedding is observed and the fluctuating across-wind load on the downstream building decreases. For larger distance ($X/D{\geq}3$), strong correlation between the across-wind load of the downstream building and the oscillation of the wake of the upstream building is found. By further analysis with conditional sampling and phase-averaged techniques, the coherent flow structures in the building gap are clearly observed and the wake oscillation of the upstream building is confirmed to be the reason of the magnified across-wind force on the downstream building. For efficient PIV measurement, the experiments use a square-section high-rise building model with geometry scale smaller than the usual value. Interference factors for all three components of wind loads on the building models being surrounded by another identical building with various configurations are measured and compared with those from previous studies made at large geometry scale. The results support that for interference effect between buildings with sharp corners, the length scale effect plays a minor role provided that the minimum Reynolds number requirement is met.

• Journal of The Korea Institute of Healthcare Architecture
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• v.28 no.4
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• pp.89-97
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• 2022

Purpose: Because of the recent COVID-19 pandemic, there have been many cases of using portable negative pressure unit to convert general wards into temporary negative pressure isolation wards. The purpose of this study is to analyze the indoor environment of the switching type wards. Methods: Field measurements and experiments were conducted in a medical facility. Air volume, wind speed and pressure difference were measured in non-occupant state. Dispersion tests were performed with gas and particle matter. Results: The pressure difference between the wards and the corridor was higher than -2.5 Pa in normal situation. However, in the gas and particle dispersion tests, it was found that there were concerns about the spread through leakages in low-airtight walls or ceilings. In addition, it was confirmed that the pressure imbalance in ducts through the non-sealed diffusers could cause back flow during portable unit operation. Furthermore, when there was a pressure difference between adjacent wards planned to be at same pressure level, the possibility of the spread through the leakages was found. Implications: When using portable units for making switching type wards, it is necessary to create airtight space and seal the non-operation diffusers. In case of operating the air handling unit, T.A.B must be performed to adjust the duct balancing.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.118-125
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• 2023

The wind tunnel test is one of the essential processes in the development of guided missile systems, and various wind tunnel facilities exist depending on the test requirements, various conditions, and their purposes. The Ludwieg tube is very useful in the development of guided missile systems, and we have necessitated the upgrade of the Ludwieg tube in ADD to acquire various test requirements, such as high angle of attack, repeatability, and stability. In this paper, upgrading the nozzle, vacuum tank, and model support is suggested to improve the Ludwieg tube performance, and we demonstrate a result of the solution through pressure measurement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.417-422
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• 2017

One of the most frightening aspects of weapons of mass destruction (WMD) is their ability to cause death in very small quantities without being visible to the public. The military authorities are making considerable effort to ensure the survivability of the combatants in the event of NBC(Nuclear, Biological and Chemical) contamination. Therefore, in this study, modules were developed for the measurement of the positive pressure and for the detection of the chemicals used for the control of the various shut-off valves used in an NBC shelter. In addition, a high performance gas tight shut-off valve was developed that can overcome the disadvantages associated with manual manufacturing, such as the occurrence of defective products and high manufacturing cost. By applying the positive pressure measurement and chemical detection modules, this valve was able to be used to control the facility. The developed gas-tight shut-off valve maintained airtight characteristics at a pressure loss of 28[Pa] at the prescribed wind velocity and an internal pressure of 30[kPa]. It is expected to be possible to control the gas-tight shut-off valve through the remote measurement of the positive pressure, thereby ensuring the foreign independence of import substitution and defense related technology in the future. In addition, by installing these valves in all of the intake ports or exhaust ports connected to the outside of the NBC shelter, it is possible to prevent the damage resulting from the rapid inflow of the storm pressure caused by conventional weapons and nuclear explosions, thereby protecting the people and equipment in the shelter.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.273-283
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• 2018

Currently, the dynamic amplification effect of suction is described using the wind vibration coefficient (WVC) of external loads. In other words, it is proposed that the fluctuating characteristics of suction are equivalent to external loads. This is, however, not generally valid. Meanwhile, the effects of the ventilation rate of louver on suction and its WV are considered. To systematically analyze the effects of the ventilation rate of louver on the multi-dimensional WVC of ultra-large cooling towers under suctions, the 210 m ultra-large cooling tower under construction was studied. First, simultaneous rigid pressure measurement wind tunnel tests were executed to obtain the time history of fluctuating wind loads on the external surface and the internal surface of the cooling tower at different ventilation rates (0%, 15%, 30%, and 100%). Based on that, the average values and distributions of fluctuating wind pressures on external and internal surfaces were obtained and compared with each other; a tower/pillar/circular foundation integrated simulation model was developed using the finite element method and complete transient time domain dynamics of external loads and four different suctions of this cooling tower were calculated. Moreover, 1D, 2D, and 3D distributions of WVCs under external loads and suctions at different ventilation rates were obtained and compared with each other. The WVCs of the cooling tower corresponding to four typical response targets (i.e., radial displacement, meridional force, Von Mises stress, and circumferential bending moment) were discussed. Value determination and 2D evaluation of the WVCs of external loads and suctions of this large cooling tower at different ventilation rates were proposed. This study provides references to precise prediction and value determination of WVC of ultra-large cooling towers.

• The Journal of the Acoustical Society of Korea
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• v.31 no.4
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• pp.253-259
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• 2012

Goldingham's measurement of the velocity of sound undertaken in the early nineteenth century was the first large-scale measuring enterprise which considered various meteorological factors such as temperature, humidity, atmospheric pressure, the direction of the wind, etc. Goldingham's successful performance of measuring the velocity of sound by employing the sounds of cannons as sound source in Madras (now Chennai), a colonial region of India, for one and a half years was supported by material, institutional and social resources. As the official astronomer at the Madras Observatory, he was benefitted by the undemanding employment of accurate measuring instruments under the support of the Madras Army enabled him to gain reliable data and his reputation as professional experimentalist facilitated the acknowledgment of their trustworthiness.