굴절 버스 조향을 고려한 회전 교차로 통과시의 주행 폭원 분석

박재홍,윤천주,노민형,성정곤 한국도로학회 2022 한국도로학회논문집 Vol.24 No.6

PURPOSES : The turning movement of vehicles is directly affected by such factors as vehicle length, wheelbase, steering angle, articulated angle, and wheel steering. Therefore, it is necessary to analyze the impact of changes in each factor on the turning of the vehicle. Because a vehicle with a long body, such as an articulated bus, makes a wide turn, this study analyzes the swept path of the driving vehicle considering the specifications of the vehicle. METHODS : This study was conducted by dividing driving routes into four routes of two-lane four-way roundabouts, and the turning conditions were examined for six types (Type 1–6) that simulated actual articulated bus data. The same vehicle specifications as those of the actual articulated bus were applied to the road design simulation (AutoTURN Pro), and the width of the swept path for the articulated bus was investigated based on the wheel steering control. Using a virtual reference line for dividing the inscribed circle into lanes of the roundabout by 5°, the driving width of the swept path was measured and the angle at which the driving width was largest during driving through the turning intersection was examined. In addition, the changes in the driving width of the swept path according to the wheel steering control under the same wheel turning conditions, as well as the articulated and steering angles, were investigated. RESULTS : The driving width of the swept path for the vehicle (Type 1) with the front wheel control function being an all-wheel system was less than that of an articulated bus with the largest driving width of 15° after entering the roundabout and 15° before entering the roundabout (Type 2). Furthermore, although the specifications of the vehicles were the same, it was determined that Type 5 was superior to Type 6 after reviewing the driving width in light of changes in the steering and articulated angles. CONCLUSIONS : The results of this study are expected to contribute to the field of road design considering traffic safety when large vehicles, such as articulated buses, turn on roundabouts or curved road sections.

EFFECT OF SLEEP ANGLE ON THE AERODYNAMIC FORCE GENERATION OF A NOVEL SLEEP TWIST ROUND (STR) VERTICAL BLADE FOR WIND TUEBINE

( Nanang Mahardika ),( Ja Choon Jung ),( Mi Hye Jang ) 조선대학교 공학기술연구원 2013 공학기술논문지 Vol.6 No.4

In this paper, the effect of blade``s sleep (swept) angle towards the normal force coefficient (Cn) and tangential force coefficient (Ct) is investigated by using Blade Element-Momentum Theory (BEMT)-based multiple stream tube model for rotating condition. For three different tip speed ratio (TSR), multiple stream tube model suggests that the variation in terms of standard deviation of Cn and Ct are up to 3.3 times less for the model with higher swept angle (β). For startup condition, Computational Fluid Dynamic (CFD) analysis by using commercial software is conducted to calculate the torque variation at twelve different blade positions relative to the wind direction for seven different models. Unlike the Gorlov mathematical model for helical turbine, CFD analysis predicted that the average torque is increasing as the swept angle increases. Meanwhile, the variation of torque is up to 10 times less for the models with higher swept angle. These results suggest that the implementation of swept angle can increase the fatigue life and the startup performance of the blades.

전산유체역학을 이용한 3차원 날개의 후퇴각 효과 연구

이재훈,정경진 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.4

본 연구에서는 전산유체역학을 이용한 3차원 날개의 후퇴각에 따른 공력 특성 변화를 고찰하였다. 일반적으로 고속의 비행체는 임계 마하수를 높이기 위해 날개에 후퇴각을 준다. 후퇴각의 의한 공력 특성의 효과를 알아보기 위해 NACA의 실험 데이터를 바탕으로 후퇴각이 0도 및 45도인 두 개의 날개에 대해 전산유체역학을 이용하여 공력해석을 수행하였다. 실험 결과와 공력 계수를 비교하였으며 유동 가시화를 통해 두 날개의 유동 특성의 차이를 살펴보았다. In this study the aerodynamic performance of a three-dimension swept-back wing is considered using the computational fluid dynamics(CFD) technique. Generally, the sweep-back angle is applied to a high speed aircraft to increase the critical Mach number. To study the aerodynamic characteristic of the sweptback wing, aerodynamic analysis is performed for two wings and their sweep angles are 0 and 45 degrees based on the experiment of the NACA report. Aerodynamic coefficients from CFD are compared with experimental data and difference of two wings are studied with post-processing of the analysis result.

Effect of sweep angle on bifurcation analysis of a wing containing cubic nonlinearity

Irani, Saied,Amoozgar, Mohammadreza,Sarrafzadeh, Hamid Techno-Press 2016 Advances in aircraft and spacecraft science Vol.3 No.4

Limit cycle oscillations (LCO) as well as nonlinear aeroelastic analysis of a swept aircraft wing with cubic restoring moments in the pitch degree of freedom is investigated. The unsteady aerodynamic loading applied on the wing is modeled by using the strip theory. The harmonic balance method is used to calculate the LCO frequency and amplitude for the swept wing. Finally the super and subcritical Hopf bifurcation diagrams are plotted. It is concluded that the type of bifurcation and turning point location is sensitive to the system parameters such as wing geometry and sweep angle.

전산유체/전산구조 연계 방법을 이용한 후퇴각이 있는 수평축 풍력터빈 로터 블레이드의 공탄성 특성 예측

김영진,권오준 한국신·재생에너지학회 2019 신재생에너지 Vol.15 No.3

The aeroelastic characteristics for the backward swept blade of a horizontal axis wind turbine were examined by using a coupled CFD/CSD method as the fundamental research for a bend-twist coupled (BTC) blade. The aerodynamic loads were obtained from the three-dimensional, incompressible, Navier-Stokes CFD flow solver based on unstructured meshes. The elastic behavior of the blade was calculated by using an FEM-based CSD solver utilizing a nonlinear coupled flap-lag-torsion beam theory. The calculations were made for the blade of the NREL 5MW wind turbine with backward swept angle. Compared to the straight rotor blade, flapwise deflection toward the tower and edgewise deflection toward the leading edge of the backward swept blade were decreased; otherwise, its torsional deflection in nose-down direction was significantly increased. Due to the blade deformations that decreased its effective angle-of-attack, the aerodynamic loads applied to the swept blades were remarkably reduced compared to the straight rotor blade. In addition, the root bending moments were also influenced by the swept-back configuration of the blade. Due to the aerodynamic loads reduction of the backward swept blade, the root bending moments in the edgewise and flapwise directions were decreased, although the torsional bending moments were significantly increased.

활공하는 칼새 날개의 후퇴각에 대한 공력특성

복정진,한종섭,장조원,김중관,한재흥 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.4

본 논문에서는 칼새의 활공비행에 대한 후퇴각과 레이놀즈수 효과를 확인하기 위한 공력측정을 수행하였다. 실험에 적용된 날개는 칼새 날개와 동일한 형상을 갖도록 카본플레이트를 CNC 가공하였으며, 날개의 공력을 측정하기 위해 토출식 아음속 풍동과 소형 외장형 로드셀을 적용하였다. 날개의 후퇴각을 5º, 30º, 50º로 변화시켜가며 레이놀즈수 0.9x104, 2.0x104, 3.8x104에 대하여 공력을 측정하였으며, 받음각은 0-90º 범위를 측정하였다. 공력측정을 통해 칼새날개는 낮은 레이놀즈수 영역임에도 불구하고 레이놀즈수 효과가 크지 않다는 사실을 파악하였으며, 후퇴각의 변화에 따라 공력특성이 현격히 변화하는 것을 알 수 있었다.

The effect of sweep angle on the limit cycle oscillations of aircraft wings

Eken, Seher,Kaya, Metin Orhan Techno-Press 2015 Advances in aircraft and spacecraft science Vol.2 No.2

This study focuses on the limit cycle oscillations (LCOs) of cantilever swept-back wings containing a cubic nonlinearity in an incompressible flow. The governing aeroelastic equations of two degrees-of-freedom swept wings are derived through applying the strip theory and unsteady aerodynamics. In order to apply strip theory, mode shapes of the cantilever beam are used. The harmonic balance method is used to calculate the frequencies of LCOs. Linear flutter analysis is conducted for several values of sweep angles to obtain the flutter boundaries.

전익기 형상의 앞전후퇴각 변화에 따른 공력해석

이재문(J.M. Lee),장조원(J.W. Chang) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.4

A computational study was carried out in order to investigate aerodynamic characteristics on leading edge sweepback angles of Flying-Wing configurations. The viscous-compressible Navire-Stokes equation and Spalart-Allmaras turbulence model of the commercial CFD code were adopted for this computation analysis. This investigation examined aerodynamic characteristics of three different types of leading edge sweepback angles: 30°, 35° and 40°. The freestream Mach number was M=0.80 and the angle of attack ranged from a=0° to a=20°. The results show that the increases in sweepback angle of the Flying-Wing configuration creates more efficient aerodynamic performance.

방파제 연계형 30kW급 파력발전용 임펄스터빈의 설계와 성능평가

김길원,홍기용,김경환,현범수 한국해양환경·에너지학회 2019 한국해양환경·에너지학회지 Vol.22 No.3

진동수주형 파력발전장치는 간단한 에너지변환 구조와 유지보수의 용이성 때문에 타 파력발전장치에 비해 상용화에 가장 근접한 장치이다. 본 논문은 도서지역의 방파제에 연계할 파력발전장치의 2차 에너지변환장치로서 임펄스터빈을 설계하고 성능평가 함을 목적으로 한다. 먼저 적지해역과 방파제의 규모에 적합한 기당 30 kW급 발전장치용 임펄스터빈의 개념설계를 수행하고 용수파력발전장치 설계에서 사용한 Hong et al.[2016] 의 연구방법론을 바탕으로 직경을 도출 하였으며, 수치해석을 통하여 다양한 설계변수의 민감도 해석을 진행하였다. 이를 바탕으로 도출된 기본 임펄스터빈의 형상에 더하여 날개 스팬방향으로 뒤젖힘각을 적용한 로터형상과 그 끝단에 링을 부착한 링형(Ring-type) 터빈 형상을 수치해석적 방법으로 제안하여 총 3개의 후보터빈을 도출하였다. 도출된 터빈들의 성능검증을 위하여 왕복유동이 재현 가능한 풍동에서 실험을 실시하여 각 터빈의 성능을 다양한 입력조건에서 평가하였고, 그중 링형 터빈이 설계점에서 최대 52.9%의 우수한 터빈 효율을 주는 것으로 확인하였다. The present study deals with the design and performance analysis of three different impulse turbines for 30 kW-class Oscillating Water Column (OWC) wave energy converter applicable to breakwater. Conceptual design was made by using the look-up table method of Hong et al.[2016] previously applied to Yongsoo Wave Power Plant. For the basic design, FLUENT-based numerical analysis tool was utilized to design a conventional-type impulse turbine by optimizing the design parameters such as number of blade, angle of guide vane, hub ratio and tip clearance. Two more models were designed by modifying the conventional-type to enhance the efficiency of turbines. Firstly, a ring-type turbine was proposed to minimize the vortex roll-up near the tip of rotor blade. The depth of penetration, thickness and length of ring were optimized numerically. Secondly, a sweep angle-type turbine designed by Yang et al.[2017] was considered as one of the candidates. Numerically designed three turbines were then validated experimentally using a specially-built reciprocating flow generator to simulate the wave movement inside OWC. It was found that while both ring-type and sweep angle-type turbines gave the better efficiency than the conventional-type, a ring-type turbine was finally selected as the best one which shows approximately 52.9% in peak efficiency.

Repeatability and Agreement of Chord Mu between Scheimpflug Tomography and Swept-Source Optical Coherence Tomography

Na Hyun Kim,Hyun Jin Kim,Soo Chang Cho,Kyung Eun Han 대한안과학회 2023 Korean Journal of Ophthalmology Vol.37 No.6

Purpose: To evaluate repeatability and agreement of chord mu between Scheimpflug tomography (Pentacam HR) and sweptsource optical coherence tomography–based optical biometer (IOLMaster 700). Methods: In this retrospective study, 63 eyes from 33 patients were included. Chord mu, X and Y Cartesian distances between the corneal vertex and the pupil center (Px and Py), and the pupil diameter were compared using two instruments. Repeatability was evaluated using intraclass correlation coefficient (ICC), coefficient of variation (CoV), and within-subject standard deviation (Sw). Interdevice agreement was evaluated using paired t-tests and Bland-Altman plots. Results: Although Sw values for all parameters were similar between the two devices, CoV values of chord mu and pupil diameter were lower, and ICC values of those parameters were higher, in the IOLMaster 700 than in the Pentacam HR. Chord mu and pupil diameter values were higher in IOLMaster 700 than Pentacam HR (p < 0.01). The width of the 95% limit of agreement was wide for all parameters. Conclusions: IOLMaster 700 showed better repeatability than Pentacam HR in chord mu, Px, Py, and pupil diameter values. Because there were statistically significant differences and a low level of agreement in chord mu and pupil diameter values between the two devices, they cannot be used interchangeably.