• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.679-684
• /
• 2004

Numerical analysis of aerodynamic characteristics was differently performed according to the running situation of the Korean Tilting Train eXpress (TTX) that would be introduced for an improvement in efficiency of the used railroad track. Fluent6.0 was used for the analysis of Non-tilting case, Tilting case and Passing-by case with the model of TTX. As a result, the aerodynamic drag had little difference between Tilting and Non-tilting case. However, pressure contour under the train of Tilting case was not symmetry because the gap between a train and the ground was different at both sides. And this disparity of pressure worked on the side force. In Passing-by case attraction and counterattraction occurred alternately and affected to the opposite train. When two trains were side by side, the maximum attraction was generated especially. Through an analysis of pressure wave in tunnel a large variation of pressure was generated by the bluff nose of TTX. The results in this study would be good data for the aerodynamic characteristic on TTX and provide important information to judgment of running safety.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.25-32
• /
• 2005

The aerodynamic loads at the blade hub and the drive shaft for 1MW horizontal axis wind turbine are calculated numerically. The geometric shape of the blade such as chord length and twist angle can be obtained fran the aerodynamic optimization procedure. Various airfoil data, that is thick airfoils at hub side and thin airfoils at tip side, are distributed along the spanwise direction of the rotor blade. Under the wind data fulfilling design load cases based on the IEC61400-1, all of the shear forces, bending moments at the hub and the low speed shaft of the drive train are obtained by using the FAST code. It shows that shear forces and bending moments have a periodic. trend. These oscillating aerodynamic loads will lead to the fatigue problem at both of the hub and drive train From the load analysis the maximum shear forces and bending moments are generated when wind turbine generator system operates in the case of the extreme speed wind condition.

• Wind and Structures
• /
• v.26 no.6
• /
• pp.355-367
• /
• 2018

This paper studies the aerodynamic stability of a tensioned, geometrically nonlinear orthotropic membrane structure with hyperbolic paraboloid in sag direction. Considering flow separation, the wind field around membrane structure is simulated as the superposition of a uniform flow and a continuous vortex layer. By the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics, aerodynamic pressure acting on membrane surface can be determined. And based on the large amplitude theory of membrane and D'Alembert's principle, interaction governing equations of wind-structure are established. Then, under the circumstance of single-mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction governing equations into a system of second-order nonlinear differential equation with constant coefficients. Through judging the frequency characteristic of the system characteristic equation, the critical velocity of divergence instability is determined. Different parameter analysis shows that the orthotropy, geometrical nonlinearity and scantling of structure is significant for preventing destructive aerodynamic instability in membrane structures. Compared to the model without considering flow separation, it's basically consistent about the divergence instability regularities in the flow separation model.

• Wind and Structures
• /
• v.22 no.1
• /
• pp.1-16
• /
• 2016

The paper presents the state-of-the-art in aerodynamic performance of the modern horizontal axis wind turbine. The study examines the different complexities involved with wind turbine blade aerodynamic performance in open atmosphere and turbine wakes, and highlights the issues which require further investigations. Additionally, the latest concept of smart blades and frequently used wind turbine design analysis tools have also been discussed. The investigation made through this literature survey shows significant progress towards wind turbine aerodynamic performance improvements in general. However, still there are several parameters whose behavior and specific role in regulating the performance of the blades is yet to be elucidated clearly; in particular, the wind turbulence, rotational effects, coupled effect of turbulence and rotation, extreme wind events, formation and life time of the wakes.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.10a
• /
• pp.177-180
• /
• 2004

The development of a tilting train with construction of electric line on the conventional railway is required for speed-up on the conventional railway with many curving sections. For development of tilting train, the study and development of the tilting system and tilting bogie having the different mechanism with a general high speed train will play a main role for improving the technology in the field of Korean railway The study and development of the pantograph tilting mechanism in order to keep a good contact behavior between a pantograph and a contact wire by tilting a pantograph on the opposite direction of the vehicle tilting direction. In this study, we analyzed the aerodynamic characteristic of a developing pantograph on the tilting train and obtained the contact force with catenary by aerodynamic lift force by the aerodynamic analysis. We also performed the numerical analysis for design the device controlling lift force on a pantograph. From the aerodynamic simulation and parameter study for a device to control the lift force, we will suggest the various shape and the optimal shape of it corresponding to a developing tilting pantograph. The Fluent software is used for the calculation of flow profile in this study.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.467-471
• /
• 2004

The development of a tilting train with construction of electric line on the conventional railway is required for speed-up on the conventional railway with many curving sections. For development of tilting train, the study and development of the tilting system and tilting bogie having the different mechanism with a general high speed train will play a main role for improving the technology in the field of Korean railway. The study and development of the pantograph tilting mechanism in order to keep a good contact behavior between a pantograph and a contact wire by tilting a pantograph on the opposite direction of the vehicle tilting direction. In this study, we analyzed the aerodynamic characteristic of a developing pantograph on the tilting train and obtained the contact force with catenary by aerodynamic lift force by the aerodynamic analysis. We also performed the numerical analysis for design the device controlling lift force on a pantograph. From the aerodynamic simulation and parameter study for a device to control the lift force, we will suggest the various shape and the optimal shape of it corresponding to a developing tilting pantograph. The Fluent software is used for the calculation of flow profile in this study.

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

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.5
• /
• pp.391-398
• /
• 2016

This study focused on the aerodynamic loads of the horizontal axis wind turbine blade due to the normal turbulence inflow condition. Normal turbulence model (NTM) includes the variations of wind speed and direction, and it is characterized by turbulence intensity and standard deviation of flow fluctuation. IEC61400-1 recommends the fatigue analysis for the NTM and the normal wind profile (NWP) conditions. The aerodynamic loads are obtained at the blade hub and the low speed drive shaft for MW class horizontal axis wind turbine which is designed by using aerodynamically optimized procedure. The 6-components of aerodynamic loads are investigated between numerical results and load components analysis. From the calculated results the maximum amplitudes of oscillated thrust and torque for LSS with turbulent inflow condition are about 5~8 times larger than those with no turbulent inflow condition. It turns out that the aerodynamic load analysis with normal turbulence model is essential for structural design of the wind turbine blade.

• Wind and Structures
• /
• v.12 no.4
• /
• pp.285-298
• /
• 2009

For long-span suspension bridges with their intrinsic limit in flutter, some counter measures, for example, central stabilizers, should be adopted to improve aerodynamic stability to meet with the appropriate wind resistance requirements. The present paper introduces aerodynamic stabilization for long-span suspension bridges with box girders by using central stabilizers based on Xihoumen Bridge with the main span of 1650 m. The aerodynamic stabilization study covers experimental investigation of sectional model testing, comprehensive evaluation of three central stabilizers and theoretical analysis of stabilizing mechanism related to flutter derivatives, aerodynamic damping and degree participation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2002.04a
• /
• pp.140-145
• /
• 2002

At present, wind tunnel test or CFD is used for predicting aerodynamic drag coefficient in motor company. But, wind tunnel test requires much cost and time, and CFD has about 30% error. In this study a predicting program of the aerodynamic drag coefficient based on empirical techniques was developed. Also a mathematical optimization method using GRG method was added to the program. The program was applied to six cars. Aerodynamic drag coefficient values of six cars were Predicted with 4.857% average error. The optimization method was also applied to six cars. Three parameters selected from sensitivity analysis were determined to reduce the afterbody drag coefficient to the value established by a designer and when some parameters were changed for a developing automotive, optimal modifiable parameters were determined to preserve the same drag coefficient as the original automotive. It was verified that this program could predict the aerodynamic drag coefficient effectively and accurately, and this program with GRG method could determine optimal values of parameters.