• Wind and Structures
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• v.28 no.5
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• pp.331-345
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• 2019

Long-span bridge decks are often shaped as streamlined to improve the aerodynamic performance of the deck. There are a number of important shaping parameters for a streamlined bridge deck. Their effects on aerodynamics should be well understood for shaping the bridge deck efficiently and for facilitating the bridge deck design procedure. This study examined the effect of various shaping parameters such as the bottom plate slope, width ratio and side ratio on aerodynamic responses of single box streamlined bridge decks by employing unsteady RANS simulation. Steady state responses and flow field were analyzed in detail for wide range of bottom plate slopes, width and side ratios. Then for a particular deck shape Reynolds number effect was investigated by varying its value from $1.65{\times}10^4$ to $25{\times}10^4$. The aerodynamic response showed very high sensitivity to the considered shaping parameters and exhibited high aerodynamic performance for a particular combination of shaping parameters.

• Wind and Structures
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• v.38 no.3
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• pp.161-170
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• 2024

In recent years, there have been an increasing number of experimental studies showing the need to include robustness criteria in the design process to develop complex active control designs for practical implementation. The paper investigates the crosswind aerodynamic parameters after the blocking phase of a two-dimensional square cross-section structure by measuring the response in wind tunnel tests under light wind flow conditions. To improve the accuracy of the results, the interpolation of the experimental curves in the time domain and the analytical responses were numerically optimized to finalize the results. Due to this combined effect, the three aerodynamic parameters decrease with increasing wind speed and asymptotically affect the upper branch constants. This means that the aerodynamic parameters along the density distribution are minimal. Taylor series are utilized to describe the fuzzy nonlinear plant and derive the stability analysis using polynomial function for analyzing the aerodynamic parameters and numerical simulations. Due to it will yield intricate terms to ensure stability criterion, therefore we aim to avoid kinds issues by proposing a polynomial homogeneous framework and utilizing Euler's functions for homogeneous systems. Finally, we solve the problem of stabilization under the consideration by SOS (sum of squares) and assign its fuzzy controller based on the feasibility of demonstration of a nonlinear system as an example.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.163-167
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• 2005

A research to evaluate efficiency of design optimization was performed for aerodynamic design optimization problem in distributed computing environment. The aerodynamic analyses which take most of computational work during design optimization were divided into several jobs and allocated to associated PC clients through network. This is not a parallel process based on domain decomposition rather than a simultaneous distributed-analyses process using network-distributed computers. GBOM(gradient-based optimization method), SAO(Sequential Approximate Optimization) and RSM(Response Surface Method) were implemented to perform design optimization of transonic airfoil and to evaluate their efficiencies. One dimensional minimization followed by direction search involved in the GBOM was found an obstacle against improving efficiency of the design process in distributed computing environment. The SAO was found quite suitable for the distributed computing environment even it has a handicap of local search. The RSM is apparently the fittest for distributed computing environment, but additional trial and error works needed to enhance the reliability of the approximation model are annoying and time-consuming so that they often impair the automatic capability of design optimization and also deteriorate efficiency from the practical point of view.

• Wind and Structures
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• v.6 no.3
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• pp.179-196
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• 2003

A long suspension bridge is often located within a unique wind environment, and strong winds at the site seldom attack the bridge at a right angle to its long axis. This paper thus investigates the buffeting response of long suspension bridges to skew winds. The conventional buffeting analysis in the frequency domain is first improved to take into account skew winds based on the quasi-steady theory and the oblique strip theory in conjunction with the finite element method and the pseudo-excitation method. The aerodynamic coefficients and flutter derivatives of the Tsing Ma suspension bridge deck under skew winds, which are required in the improved buffeting analysis, are then measured in a wind tunnel using specially designed test rigs. The field measurement data, which were recorded during Typhoon Sam in 1999 by the Wind And Structural Health Monitoring System (WASHMS) installed on the Tsing Ma Bridge, are analyzed to obtain both wind characteristics and buffeting responses. Finally, the field measured buffeting responses of the Tsing Ma Bridge are compared with those from the computer simulation using the improved method and the aerodynamic coefficients and flutter derivatives measured under skew winds. The comparison is found satisfactory in general.

• Journal of computational fluids engineering
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• v.11 no.2 s.33
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• pp.19-24
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• 2006

A research to evaluate the efficiency of design optimization was carried out for aerodynamic design optimization problem in distributed computing environment. The aerodynamic analyses which take most of computational work during design optimization were divided into several jobs and allocated to associated PC clients through network. This is not a parallel process based on domain decomposition in a single analysis rather than a simultaneous distributed-analyses using network-distributed computers. GBOM(gradient-based optimization method), SAO(Sequential Approximate Optimization) and RSM(Response Surface Method) were implemented to perform design optimization of transonic airfoils and evaluate their efficiencies. dimensional minimization followed by direction search involved in the GBOM was found an obstacle against improving efficiency of the design process in the present distributed computing system. The SAO was found fairly suitable for the distributed computing environment even it has a handicap of local search. The RSM is apparently the most efficient algorithm in the present distributed computing environment, but additional trial and error works needed to enhance the reliability of the approximation model deteriorate its efficiency from the practical point of view.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.1-8
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• 2004

In this study, the method of computing and extracting the generalized unsteady aerodynamic matrices using MSC/NASTRAN and MSC/NASTRAN DMAP ALTER has been suggested for the analysis and control of aeroelastic phenomena such as flutter and gust response analysis. In addition to that, the method of approximating the generalized unsteady aerodynamic matrices using minimum state approximation method has been proposed in order to cast the aeroelastic equations of motion in state space form for aeroelastic analysis and control application. Simplified aircraft wing box model has been used for the validation of the methods suggested in this study.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.127-139
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• 2000

Transient aerodynamic response of an airfoil to a rapidly deploying spoiler is numerically investigated using a two-dimensional turbulent compressible Navier-Stokes flow model. The spoiler moving relative to a stationary airfoil is treated by an overset grid bounded by a 'dynamic domain-dividing line' the concept of which is developed first..in this paper. The fluid-dynamic mechanism of the adverse lift due to the rapidly deploying spoiler is analyzed. Also the effect of spoiler deploying rate on the initial behavior of the aerodynamic response is expounded, which is of interest in view of active control technology and controller design for the spoiler. The results of present computation about the stationary as well as moving spoilers are relatively in good agreement with the existing experimental data.

• Wind and Structures
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• v.5 no.6
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• pp.479-492
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• 2002

A finite element aerodynamic model that can be used to analyse flutter instability of long span bridges in the time domain is presented. This approach adopts a simplified quasi-steady formulation of the wind forces neglecting the vortex shedding effects. The governing equations used are effective only for reduced velocities $V^*$ sufficiently great: this is generally acceptable for long-span suspension bridges and, then, the dependence of the wind forces expressions of the flutter derivatives can be neglected. The procedure describes the mechanical response in an accurate way, taking into account the non-linear geometry effects (large displacements and large strains) and considering also the compressed locked coil strands instability. The time-dependence of the inertia force due to fluid structure interaction is not considered. The numerical examples are performed on the three-dimensional finite element model of the Great Belt East Bridge (DK). A mode frequency analysis is carried out to validate the model and the results show good agreement with the experimental measurements of the full bridge aeroelastic model in the wind tunnel tests. Significant parameters affecting bridge response are introduced and accurately investigated.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.227-228
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• 2008

In the present paper, fowler flap was optimized to maximize the lift with response surface method. Leading edge shape and the gap between main airfoil and flap, were optimized and the aerodynamic characteristics was improved considerably. The optimized flap has more rounded leading edge and bigger gap. Before angle of attack, $10^{\circ}$, lift and drag are improved and the optimized flap shows similar aerodynamic characteristics to the original flap. The flow condition for optimization was angle of attack, $10^{\circ}$, Mach number, 0.2, flap deflection, $40^{\circ}$.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.193-196
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• 2004

Numerical optimization method of long endurance airfoil has been performed with a RSM(Response Surface Method) for smart UAV wing design. For the base line airfoil, NACA 64621 airfoil was selected and optimized to satisfy long endurance condition for smart UAV Aerodynamic coefficients required for RSM are obtained by using 2-D Navier-Stokes solver with Spalart-Allmaras turbulence model. The optimized airfoil showed increased maximum lift and endurance factors together with reasonable thickness ratio.