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4각 덕트의 입구영역에서 천이 정상유동의 입구길이에 관한 연구
박길문,유영태,고영하,Park, G.M.,Yoo, Y.T.,Koh, Y.H. 대한설비공학회 1990 설비공학 논문집 Vol.2 No.1
In the present study, the entrance length, velocity profiles and waveforms of developing transitional steady flows in a square duct are investigated analytically and experimentally. The systems of conservation equations for transitional steady duct flows are solved analytically by linearizing non-linear convective terms and adoption of modified eddy viscosity from empirical correlations. Analytical solutions of velocity profiles for developing transitional steady flow were obtained in the form of infinite series. The experimental study for transitional steady flow in a square duct with $40mm{\times}40mm{\times}4000mm$($width{\times}height{\times}length$) was carried out to measure velocity profiles and other parameters by using a hot-wire anemometer with data acquisition and processing system. The entrance length of developing transitional steady flows in a square duct was $L_e{\fallingdotseq}0.02{\cdot}Re,st{\cdot}D_h$, and the overshoot was occured at about 30 times of hydraulic diameter because of the effect of external velocity of boundary layer and instantaneous acceleration.
정사각단면 $180^{\circ}$ 곡관덕트의 입구영역에서 비정상층류유동의 유동특성에 관한 연구
박길문,모양우,조병기,Park, G.M.,Mo, Y.W.,Cho, B.K. 대한의용생체공학회 1996 의공학회지 Vol.17 No.4
The flow characteristics of developing unsteady laminar flow in a square-sectional $180^{\circ}$ curved duct are experimentally investigated by using laser doppler velocimerty (LDV) system with data acquisition and processing system of rotating machinery resolver(RMR) and PHASE software. The major flow characteristics of developing laminar pulsating flows are presented by mean velocity profilel velocity distribution of secondary flow, wall shear stress distributions, entrance lengths according to dimensionless angular frequency($\omega^+$), velocity amplitude ratio($A^1$), and time-averaged Dean number($De_ta$). The velocity profiles and wall shear stress distribution of laminar pulsating flow with dimensionlessangular frequency show the flow characteristics of the quasi-steady laminar flow in a curved duct. The developing region of laminar pulsatile flows in a square-sectional $180^{\circ}$ curved duct is extended to the curved duct angle of approximately $120^{\circ}$ under the present experimental condition.
박길문,박선종,최주호,유영태,Park, G.M.,Park, S.J.,Choi, J.H.,Yoo, Y.T. 대한설비공학회 1989 설비공학 논문집 Vol.1 No.3
A system of conservation equations for steady, oscillatory and pulsating duct flows are solved analytically by linearizing non-linear convective terms. Analytical solutions of velocity profiles for these flows are obtained in the form of infinite series. The experimental study for the air flow in a square duct ($40mm{\times}40mm$ and 400 mm long) is carried out to measure velocity profiles and other parameters by using a hot-wire anemometer with data acquisition and processing system. Major characteristics of the flows such as the classification of flow patterns, determination of critical Reynolds number and velocity profiles is accomplished from the experismental results.
박길문,고영하,Park, G.M.,Go, Y.H. 대한설비공학회 1990 설비공학 논문집 Vol.2 No.3
Turbulent characteristics of turbulent pulsating flows were studied experimentally in a square duct. Velocity waveforms, velocity profiles, and turbulent intensity of turbulent pulsating flow were investigated by using a hot-wire anemometer with data acquisition and a processing system in a square duct with a ratio of 1 ($40mm{\times}40mm$) to 4,000mm long. Turbulent components were shown to be larger in decelerating than in accelerating regions and also larger for a large phase of velocity and U'rms distribution of turbulent flow. The effect of velocity amplitude ratio does not exist for specified time [${\theta}(z^{\prime})$], amplitude ratio (${\mid}U^{\prime}_{rms.os.1}{\mid}/{\mid}U_{m.os.1}{\mid}$), and phase difference (${\Delta}U^{\prime}_{rms.os.1}-{\Delta}U_{m.os.1}$) in either turbulent oscillating or cross-sectional mean velocity components. The effect of dimensionless angular frequency for specified time [${\theta}(z^{\prime})$] can be disregarded because the dimensionless angular frequency does not affect the specified time. The velocity distributions of turbulent pulsating flows for various time-averaged Reynolds numbers are in approximate agreement with the velocity distributions for equivalent Reynolds numbers and 1/7th power law of steady flow.
정한별 ( H B Jung ),박길문 ( G M Park ),고현선 ( H S Go ),김노형 ( N H Kim ),이행남 ( H N Lee ) 조선대학교 공학기술연구원 2008 공학기술논문지 Vol.1 No.1
The exhaust noise occurs when the exhaust gas generated from the automobile engine is transmitted to the air through the exhaust system and the tail pipe. This kind of exhaust noise have a great effects on the inside and outside noise of the automobile. Designing a automobile muffler make importance of muffler performance such as transmission loss but it is difficult to develop a muffler considering only a transmission loss. In this study using the GT-Power, the gasoline engine-model noise analysis program, we analyzed the exhaust sound and back pressure followed by the shape condition of inlet pipe of the muffler. Expecting the exhaust noise using this noise analysis program can cut costs and curtail the developing period of the muffler.