Research Areas > External Flow and Wind Engineering

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Drag reduction of a tractor-trailer vehicle using gap fairings

Post Image  The gap fairing devised in this study exhibits 16.4% drag reduction at maximum with changing gap length and deflecting angle. The aero cab fairing (ACF) which combines CRF and gap fairing, and the extended aero cab fairing (EACF) considerably reduce the drag coefficient by approximately 11.1% and 17.5%, respectively. The proposed gap fairings including ACF and EACF significantly reduce mean velocity, vorticity in the gap region between tractor and trailer, and turbulent kinetic energy on the front surface of the trailer. The present results would provide useful information for im...   내용 보기

Bio-inspired cab-roof fairing of heavy vehicles for enhancing drag reduction and driving stability

Post Image  A major challenge hindering the advancement of the automotive industry is finding a way to reduce the aerodynamic drag of transport vehicles, thereby promoting fuel saving and environmental pollution control. The advanced bio-inspired CRF considerably reduced the drag coefficient of the 15-ton by approximately 20%. The side force was also reduced by up to 8% for the 15-ton at a yaw angle of ϕ = 3°. The bio-inspired CRFs significantly reduced the regions of separated shear flow and turbulent kinetic energy level on the side surfaces of the vehicle models. The findings prov...   내용 보기

화물차 운행 중 연료저감을 위한 공기저항 및 공기와류 저감장치 기술개발

화물차 운행 중 연료저감을 위한 공기저항 및 공기와류 저감장치 기술개발   내용 보기

Autorotation flight of maple samaras

Post Image Some winged seeds exhibit autorotation flight during their descent to migrate far away from the parent trees by oncoming wind. In this study, several prominent features of the autorotation flight were investigated experimentally. Velocity fields of the flow around an autorotating maple samaras model were measured by PIV technique with controlling wind speed to be similar to the descending velocity. As a result, a highly stable LEV is attached on the leeward side of the autorotating seed.   내용 보기

Flow control of turbulent jet flow using various devices

Post Image Jet flows have many practical applications. There are various flow control techniques. We have investigated the turbulence reduction in mixing layer of a plane jet using a thin wire, jet propagation through various mesh screens and vortex structure of jet issuing from wavy nozzle.Figure description (a) Plane jet facility with wavy nozzle(b) Visualized jet flow at Y = λ/2(c) Top view of visualized wavy jet propagation from the wave edge to center region   내용 보기

PIV measurements of ventilation flow inside a real passenger car

Post Image Nowadays people spend lots of time in their car. With increasing living standards, there is a trend to pursue for a comport environment inside the car. However, since most previous studies were performed using CFD or scale-down models, the ventilation flow results are different from that in the passenger compartment of a real car. In this study, a real Hyundai NF SONATA was modified slightly to visualize and analyze quantitatively the ventilation flow inside the passenger compartment under real operation condition using a PIV system which has specially designed to measure veloc...   내용 보기

Wind tunnel experiments on dynamic response of plants to strong wind

Post Image Plants produce not only energy and food (sugar) through photosynthesis, but also provide oxygen to earth. The wind plays a key role in meteorological events. It has a major influence in the growth of plants and their reproduction by spreading the seeds. Wind-induced drag of a plant’s stem and leaves has negative effects on its growth by tearing leaves or breaking branch. As plants can not escape from such negative effects, they were optimized through history for making dynamic responses to survive and to resist against strong wind by using structural softn...   내용 보기

Wind engineering study on sheltering effect of a windbreak forest

Post Image Windbreak forest has been used for centuries for various purposes including reduction of wind speed, control of heat and moisture transfer and pollutant diffusion, improvement of climate and environment, or increase of crop yields. These functional effects of windbreaks are directly related to reduction of oncoming wind speed. However, systematic studies on the shelter effects of windbreaks have been performed only recently. Most previous experiments contain little quantitative flow information, either in laboratory wind tunnel experiments or in the field studies, because experim...   내용 보기

Autorotation of Maple Seeds

Post Image Many samaras or winged seeds such as maple seeds make autorotational flight during their fall. Autorotation is the result of a delicate equilibrium between gravity, inertia and aerodynamic forces. It is complex interrelated many parameters phenomena. Such as pitch angle, coning angle, geometry of seed, surface roughness, combination of CG & CP position. The very low descent speed of the auto-rotating maple seed has been known to be attributed to the high lift generated by leading edge vortex (LEV). Autorotation of maple seeds was observed to be very stable flight pheno...   내용 보기

Autorotation of maple samaras

Post Image Some winged seeds exhibit autorotation flight during their descent to migrate far away from the parent trees by oncoming wind. In this study, several prominent features of the autorotation flight of maple samaras were investigated experimentally. The nominal values of the dynamic motion parameters are 1.2 m/s for descent velocity, 130.9 rad/s for spinning rate, 22° for coning angle, and 1.5° for pitch angle. Velocity fields of the flow around an autorotating maple samaras were measured by PIV(particle image velocimetry) technique with controlling wind speed to be similar ...   내용 보기