• Proceedings of the KSR Conference
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• 2000.05a
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• pp.529-536
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• 2000

This paper describes the analysis of aerodynamics and the prediction of airflow induced noise around simplified pantograph. First, computational fluid dynamics (CFD) is conducted far several model to evaluate linear/nonlinear flow field characteristics due to high speed flow and the CFD results support the computational aeroacoustics. The accurate prediction of the aeroacoustic analysis is necessary for designers to control and reduce the airflow induced noise. We adopt the acoustic analogy based on Ffowcs Williams- Hawkings (FW-H) equation and predict aeroacoustic noise.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.2
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• pp.165-176
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• 2015

A numerical analysis was conducted to investigate the inlet buzz and combustion oscillation in an axisymmetric ramjet engine with wedge-type flame holders. The physical model of concern includes the entire engine flow path, extending from the leading edge of the inlet center-body through the exhaust nozzle. The theoretical formulation is based on the Farve-averaged conservation equations of mass, momentum, energy, and species concentration, and accommodates finite-rate chemical kinetics and variable thermo-physical properties. Turbulence closure is achieved using a combined scheme comprising of a low-Reynolds number k-${\varepsilon}$ two-equation model and Sarkar's compressible turbulence model. Detailed flow phenomena such as inlet flow aerodynamics, flame evolution, and acoustic excitation as well as their interactions, are investigated. Mechanisms responsible for driving the inlet buzz are identified and quantified for the engine operating at subcritical conditions.

• Phonetics and Speech Sciences
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• v.6 no.1
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• pp.105-117
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• 2014

The purpose of this study was to (1) establish a Korean adult normative database for phonatory aerodynamic measures obtained with the KayPENTAX Phonatory Aerodynamic System (PAS) Model 6600, (2) investigate the intra-subject reliability of these measures across three testing sessions, and (3) examine the effect of gender on those measures. 170 healthy normal speakers (70 men and 100 women) between the ages 18 and 49 years participated in the study. The PAS protocol of maximum phonation and voicing efficiency were conducted and 25 measures were obtained. All aerodynamic measures taken in this study demonstrated high intra-subject reliability in clinical aspect. There were no significant effect of gender in the measures related to sound pressure and subglottal pressure. However, significant differences for gender were found for phonation time, airflow rate, expiratory volume, aerodynamic power, SPL range, pitch range, mean pitch, aerodynamic resistance, and aerodynamic efficiency. Clinicians should be aware of significant gender effects in some aerodynamic parameters when interpreting the data obtained from PAS.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.374-377
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• 2007

This paper deals with a pitch control for reducing load of the wind turbine system. To make a model of the wind turbine system, the Momentum Theory and Blade Element Theory are used. Considering wind shear, wind model was also built. Due to a difference of the wind speed between upper parts and lower parts of the sweep area, overturning moment of the wind turbine is generated. So, in this paper through analyzing of the system model of the wind turbine, a control algorithm which was able to achieve both maintaining power and reducing overturning moment was proposed. Using matlab simulink, controller performance was verified.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2234-2236
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• 2001

This paper describes an implementation of a radiocontrolled airplane attitude control. To obtain the model of motion, stabilizing and control coefficients, we derive the related paramaters from aerodynamics, propulsion, gravity, wind correction and atmosphere. In this model, after separating longitudinal axis and lateral axis, we can get longitudinal axis model and lateral axis model by using actuator and dynamic characteristics of engine. From these two models, we experiment two divided parts-linear part, and nonlinear part.

• Wind and Structures
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• v.37 no.4
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• pp.255-274
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• 2023

The aim of this paper is to enhance the accuracy of predicting time-averaged external surface pressures on low-rise buildings by utilizing Computational Fluid Dynamics (CFD) simulations. To achieve this, benchmark studies of the Silsoe cube and the Texas Tech University (TTU) experimental building are employed for comparison with simulation results. The paper is structured into three main sections. In the initial part, an appropriate domain size is selected based on the precision of mean pressure coefficients on the windward face of the cube, utilizing Reynolds Averaged Navier-Stokes (RANS) turbulence models. Subsequently, recommendations regarding the optimal computational domain size for an isolated building are provided based on revised findings. Moving on to the second part, the Silsoe cube model is examined within a horizontally homogeneous computational domain using more accurate turbulence models, such as Large Eddy Simulation (LES) and hybrid RANS-LES models. For computational efficiency, transient simulation settings are employed, building upon previous studies by the authors at the Windstorm Impact, Science, and Engineering (WISE) Lab, Louisiana State University (LSU). An optimal meshing strategy is determined for LES based on a grid convergence study. Three hybrid RANS-LES cases are investigated to achieve desired enhancements in the distribution of mean pressure coefficients on the Silsoe cube. In the final part, a 1:10 scale model of the TTU building is studied, incorporating the insights gained from the second part. The generated flow characteristics, including vertical profiles of mean velocity, turbulence intensity, and velocity spectra (small and large eddies), exhibit good agreement with full-scale (TTU) measurements. The results indicate promising roof pressures achieved through the careful consideration of meshing strategy, time step, domain size, inflow turbulence, near-wall treatment, and turbulence models. Moreover, this paper demonstrates an improvement in mean roof pressures compared to other state-of-the-art studies, thus highlighting the significance of CFD simulations in building aerodynamics.

• International Journal of Control, Automation, and Systems
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• v.3 no.4
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• pp.533-541
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• 2005

In this paper, a wind turbine with power splitting transmission, which is realized through a novel three-shaft planetary, is presented. The input shaft of the transmission is driven by the rotor of the wind turbine, the output shaft is connected to the grid via the main generator (asynchronous generator), and the third shaft is driven by a control motor with variable speed. The dynamic models of the sub systems of this wind turbine, e.g. the rotor aerodynamics, the drive train dynamics and the power generation unit dynamics, were given and linearized at an operating point. These sub models were integrated in a multidisciplinary dynamic model, which is suitable for control syntheses to optimize the utilization of wind energy and to reduce the excessive dynamic loads. The important dynamic behaviours were investigated and a wind turbine with a soft main shaft was recommend.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.15-24
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• 2000

The transient response of an airfoil to a rapidly deploying spoiler is numerically investigated using the turbulent compressible Navier-Stokes equations in two dimensions. Algebraic Baldwin-Lomax model, Wilcox $\kappa-\omega$ model, and SST $\kappa-\omega$ turbulence model are used to calculate the unsteady separated flow due to the rapid spoiler deployment. The spoiler motion relative to a stationary airfoil is treated by an overset grid hounded by a Dynamic Domain-Dividing Line which has been devised by the authors. The adverse effects of the spoiler influenced by the spoiler location and the hinge gap are expounded. The numerical results are in reasonably good agreement with the existing experimental data.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.1
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• pp.27-32
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• 2010

In this study, transonic flutter response characteristics have been studied for the AGARD 445.6 wing considering various turbulent models and several angle of attacks. The developed fluid-structure coupled analysis system is applied for flutter computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. The flutter boundaries of AGARD 445.6 wing are verified using developed computational system. For the nonlinear unsteady aerodynamics in high transonic flow region, DES turbulent model using the structured grid system have been applied for the wing model. Characteristics of flutter responses have been investigated for various angle of attack conditions. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.108-117
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• 2017

This paper presents a distribution simulation model for dual purpose improved conventional munitions based on flight test data. A systematic procedure for designing a dispersion simulation model is proposed. A new accumulated broken line graph was suggested for designing the distribution shape. In the process of verification and simulation for the distribution simulation model, verification was performed by first comparing data with firing test results, and an application simulation was then conducted. The Monte Carlo method was used in the simulations, which reflected the relationship between ejection conditions and real distribution data. Before establishing the simulation algorithm, the dominant ejection parameter of the submunitions was examined. The relationships between ejection conditions and distribution results were investigated. Five key distribution parameters were analyzed with respect to the ejection conditions. They reflect the characteristics of clustered particle dynamics and aerodynamics.