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장조원,전창수,김문상,이열,문희장,송병흠,김학봉,Chang, J.W.,Jeon, C.S.,Kim, M.S.,Lee, Y.,Moon, H.J.,Song, B.H.,Kim, H.B. 한국항공운항학회 2005 한국항공운항학회지 Vol.13 No.4
A closed-circuit type wind tunnel is designed, which has a test section with the dimensions $1.2(W){\times}1.2(H){\times}3.4(L)$. A subsonic wind tunnel is designed to improves educational circumstances and promote ground tests. It is constituted of an exchangeable test section, first and second diffusers, a fan, a settling chamber, a contraction, and 4 corners. The maximum velocity in the test section is 70m/s and the contraction ratio is 6.25:1. Input power in the wind tunnel is about 96.1 kw (128.8 hp) and its energy ratio is 3.89. It has the dimension of about $7.4(W){\times}3.6(H){\times}21.7m(L)$. The wind tunnel designed in this investigation will be an effective educational and investigational equipment.
이동 벽면에 의한 원형 실린더의 비대칭적 공력 발달에 관한 전산연구
정재윤(J.Y. Jung),장조원(J.W. Chang) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.3
A Computational study was carried out in order to investigate the moving wall effect of a circular cylinder at a Reynolds number of 2.0x10⁴. The viscous-incompressible Navier-Stokes equations and Spalart-Almaras turbulent model of the commercial CFD code were adopted for this numerical analysis. The moving wall was set parallel with the freestream, and moving speed was equal to the freestream velocity. The gap ratio is defined as the distance ratio between the circular cylinder diameter and the height from the moving wall. The results show that there is vortex shedding over the critical gap ratio and aerodynamic loads including amplitude and the Strouhal number change according to the gap ratio.
장조원,Chang, J.W. 한국항공운항학회 2003 한국항공운항학회지 Vol.11 No.1
The present study was carried out to develop highly efficient RC ornithopter 'Songgolmae' powered by motor and battery. Designed electric ornithopter, which has the dimension of O.88m(W)${\times}$0.56m(L)${\times}$0.15m(H), is smaller than a conventional ornithopter. This ornithopter weighs 277 grams and has 3 channels radio control. It runs on an electric motor by a lithium polymer battery and has a gear ratio of about 75${\sim}$95 to 1 to flap its 88 cm wingspan. The aerodynamic performance of the ornithopter, applied to a flapping motion only, was validated by flight tests. Flight times have exceeded 23 minutes until the battery was used up. The flight test results indicate that the ornithopter developed here has sufficient thrust to propel itself in a forward flight. From the economical point of view and the handling of the RC ornithopter, it can be said that the developed robot ornithopter is an effective RC ornithopter. This robot ornithopter flies its way high into the sky just like a real bird flies. The robot ornithopter is used for a wide range of missions.
김동하(D. H. Kim),장조원(J. W. Chang) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
An experimental study was carried out to investigate influence of flow conditions on a boundary layer to the near-wake of a flat plate. The flow condition in the vicinity of trailing edge that is influenced by upstream condition history is an essential factor that determines the physical characteristics of a near-wake. Various tripping wires were used to change boundary layer flow condition of upstream at the freestream velocity of 6.0 m/sec. Measurements of the boundary layer and near-wake according to the change of upstream conditions were conducted by using both I-probe(55P14 for boundary layer) and X-probe(55P61 for wake). Normalized velocity profiles of the boundary layer were shown the flow types such as laminar boundary layer, transition, and turbulent boundary layer at 0.95C from the leading edge. The velocity and turbulence intensity profiles of the near-wake for the case of laminar boundary layer at the flat plate surface exhibited a defect and a double peak showing perfect symmetry, respectively.
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.
장조원,변영환 한국항공운항학회 2003 한국항공운항학회지 Vol.11 No.1
A calibration jet system using separate blower is developed to calibrate a flow sensor effectively. Designed open circuit type mini calibration jet system, which has the dimension of 0.5m(W)×1.17rn(H) is small compared with conventional calibration jet systems. The exit of nozzle has exchangeable contractions with a cross section area of 38.5cm, and a cross section area of 113.1cm², respectively. The ranges of wind speed at exit of exchangeable nozzles are 7.5-42 m/s and 1.8-16.5 m/s, respectively. The input power for the high pressure blower is 1.18kW. The turning vanes for corner was rolled flat plate parallel to the flow direction. The flow conditioning screen was located immediately downstream of the wide-angle diffuser. The honeycomb and two flow conditioning screens were located in the stagnation chamber. From the economical point of view and the simplicity of the calibration jet system set up and handling, it can be said that the developed calibration jet system is an effective calibration jet system. This system can also be used to calibrate the flow sensor with high resolution.