• The KSFM Journal of Fluid Machinery
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• v.11 no.6
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• pp.54-63
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• 2008

A study on the flow characteristics in a 4-stage axial compressor and the behavior of rotating stall was experimentally performed at the third-stage rotor and stator rows in order to investigate its performance and instability of the compression system. The pressure losses generated due to the leakage flow at a tip clearance and a shroud seal clearance and the wake flow near the trailing edge of a blade were taken into consideration to estimate the causes of performance drop of the low speed research compressor(LSRC) in Seoul national university. In addition, the measurement of rotating stall was conducted with hot-wire probes and the existence and propagation of stall cell could be confirmed through fast Fourier transform and cross-correlation analysis.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2868-2872
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• 2007

In this study, a passive control using a boat-tail device is conducted for a three-dimensional car model in ground proximity. We consider various boat-tails and investigate the mechanism of drag reduction by them. By varying the length and slant angle of boat-tail, we obtain drag reductions up to 40%. From the oil-surface flow visualization and hot-wire measurement, the drag reduction by the boat-tail is characterized by the shear-layer instability and reattachment on the boat-tail, forming a small separation bubble at the upstream part of boat-tail surface, resulting in the delay of main separation and drag reduction. At high slant angles, the flow fully separates and drag is nearly same as that of no control.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.70-75
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• 2015

Swirl flow in the gun type burner has an impact on the stabilization of the flame, improvement of the combustion efficiency. The swirl flow is created by the spinner which is inside the airtube that guide the combustion air. Gun type burner has generally the inner devices composed electronic spark plug, injection nozzle, combustion device adaptor, and spinner. These inner components change the air flow behavior passing through airtube. So, this study conducted the measurement using by hot-wire anemometer and analyzed effect of the swirl number of spinner on the exhaust air of gun type burner. Turbulence characteristics come up in this study was mean velocity, turbulence intensity, kinetic energy, shear stress and flattness factor of the air flow with the change of the distance of axial direction and tangential direction from the exit of the airtube.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.819-824
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• 2001

Mean velocity and Reynolds stress components of the developing turbulent flows in a rotating 90 degree bend with square cross-section were measured by a hot-wire anemometer. Effects of the centrifugal and Coriolis forces generated by the curvature and rotation of bend on the mean motion and turbulence structures are investigated experimentally. Results show that the Coriolis force associated with the rotation of the bend may act both through the mean motion and turbulent structures, thereby changing the pressure fields, mean and turbulent velocities distributions.

• Journal of the KSME
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• v.34 no.9
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• pp.705-710
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• 1994

열.유체유동 중 난류에 대한 유동현상은 매우 광범위한 영역에서 나타나기 때문에 그 응용성이 매우 크게 작용되어 상업용 설비, 항공기, 자동차, 연소기 및 각종 스포츠 등에 이르기까지 넓게 적용되고 있다. 본 계측법은 특히 기하학적 형상에 좌우되지 않는 범용데이터 처리와 결부시켜 이용하는 것으로 최근 컴퓨터의 보급이 활발히 정착됨에 따라 보다 정확한 방법으로 난류의 정량적인 자료와 정성적인 난류구조를 계측하기 위하여 컴퓨터와 온라인으로 연결한 열선한 열 선유속계의출력을 통계해석에 의해 분석하는 방법이 시도되고 있는 것이다. 끝으로 이 글에서 언급한 삼축 열선 프로브는 프로브의 제작에 대한 고도의 기술과 프로브의 겁사체적을 되도록 작게 해야 하는 과제를 안고 있으며, 이러한 문제들은 제작기술의 발달로 점차 해결되고 있으며 적용대상이 크기 때문에 앞으로 많이 이용 될 것으로 기대되는 바이다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.483-494
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• 1998

This study describes the characteristics on impeller discharge flow of a centrifugal compressor with vaneless diffuser. Distorted flow at impeller exit was investigated by measuring of unsteady velocity fluctuation using hot-wire anemometer. As a result, a wake region appears near shroud side and moves to suction side and also to hub side as flow rate decreases. Jet, wake, and their boundary region which can be defined in jet-wake flow model are clearly observed at a high flow rate for the flow coefficient of 0.64, however, as flow rate decreases to the flow coefficient of 0.19, the classification of their regions disappears. Turbulence intensity also increases as flow rate decreases. Measurement error from uncertainty analysis is estimated about 4% at the flow coefficient of 0.19

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.4
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• pp.361-371
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• 1983

The turbulent structures of the free plane jet and two dimensional impinging jet are investigated experimentally. In order to get the two dimensional jet, the contour of the cubic equation suggested by Morel is used for a contracting nozzle. A linearized constant-temperature hot-wire anemometer is used for measurement. Mean velocities and turbulent intensities are measured along the centerline of the jet. Jet halp width spatial double velocity correlation coefficients and integral length scales are obtained. It is established that the free plane jet is truly self-preserving about 40 slot widths downstream of the nozzle. The experiments for the impinging jet are carried out at four different impingement wall locations within the self-preserving region of the free plane jet, and comparing the results with that of free plane jet, the mean velocity is changed in the region of 0.25H and turbulent intensities are affected in the region of 0.2H from the wall, respectively, where H means the distance between the nozzle exit and the wall.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3282-3292
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• 1996

Flow velocity was measured using a hot wire anemometer. Turbulence intensity was in proportion to mean flow velocity regardless of swirl velocity. And integral length scale has proportional relation with swirl velocity regardless of measurement position. Flame speed calculated by radius of visualized flame was increased and then decreased according to lapse of time from spark. Maximum flame speed was increased according to increase of turbulence intensity. Burning speed and flame transport effect increased with increase of swirl velocity, but ratio of burning speed to flame speed decreased with increased of swirl velocity. Mass fraction burned versus volume fraction burned was increased in proportion to the increase of turbulence intensity, caused by increase of combustion promotion effect according to increase of turbulence intensity and scale.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.473-478
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• 2000

In this study, the characteristics of the three-dimensional turbulent flow in a rotating square sectioned $90^{\circ}$ bend were investigated by numerical simulation and experiment. In the experimental study, the characteristics of a developing turbulent flow are measured using hot-wire anemometer to seize the rotational effects on the flow characteristics and to compare the results of computational simulation with Reynolds stress model. Each refinement is shown to lead to an appreciable improvement in the agreement between measurement and computation.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.775-778
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• 2002

In order to analyse the mechanism of a flow tone around a cavity, the correlations between the flow in the cavity and the boundary layer flow in front of the cavity are studied experimentally in this paper. The instability In the boundary layer forms the vortex at the front edge of the cavity and the flow tone is occurred by the vortex breakdown at the rear edge of the cavity Therefore, the boundary layer measurement is important in the cavity flow control. We measure the velocity of the boundary layer at the entrance of the cavity using hot-wire anemometry and the flow tone around the cavity by microphone. The boundary layer characteristic is changed by the various angle of the flap on the front edge of the cavity, while it is less influenced by the ratio of length and depth of the cavity.