• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.1061-1064
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• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• 설비공학논문집
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• 제5권4호
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• pp.235-242
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• 1993

The flow characteristics of developing turbulent pulsating flows are investigated experimentally in the entrance region of a square duct ($40mm{\times}40mm$ and 4,000mm). Mean velocity profiles, turbulence intensity and entrance length are measured by using a hot-wire anemometer system together with data acquisition and processing systems. It is found that the velocity waveforms are not changed in the fully developed flow region where that $x/Dh{\geq}40$. For turbulent pulsating flow, the turbulent components in the velocity waveforms increase as the dimensionless transverse position approaches the wall. Mean velocity profiles of the turbulent steady flows follow the one-seventh power law profile in the fully developed flow region. Turbulence intensity increases as the dimensionless transverse position increases from the center to the wall of the duct, and is slightly smaller in the accelerating phase than in the decelerating phase for the turbulent pulsating flows. The entrance length of the turbulent pulsating flow is about 40 times as large as the hydraulic diameter under the present experimental conditions.

• 대한기계학회논문집B
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• 제23권2호
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• pp.166-174
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• 1999

The flow characteristics of 2-valve and 4-valve cylinder heads with various blocked-valve were experimentally investigated in a steady flow rig. Effects of the blocked-valve configurations on flow coefficient, swirl and tumble intensity are studied. Compared to the conventional valve, the blocked valve in both cylinder heads have the much lower flow coefficient and the much higher intensity of swirl and tumble. Under the same size of blockage, the value of flow coefficient and swirl(or tumble) intensity were varied according to the position of blockage. Throughout these steady flow test the optimized positions of blockage in both cylinder heads were determined.

• Journal of Advanced Marine Engineering and Technology
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• 제15권3호
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• pp.45-56
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• 1991

This paper describes characteristics of the flow pattern of the flow past a rectangular cylinder experimentally investigated. The width-to-length ratio of the section varried from 2 to4. For the statistical treatment, autocorrelation coefficient, probability density function and power spectral density function are obtained by the digital processing technic through on-line system with a hot wire anemometer. As a results, it was found that strong periodic coherent eddies structure is sustained to about 20H downstream from the cylinder. And nearer the cylinder in the wake, the number of turbulent eddies of a large scale coherent structure are comparatively much more dominant than that of a small scale one. By the analysis of power spectrum, It was cleared that there exists a certain range of the width to length ratio between 2.5 and 3 of which the flow pattern changes abruptly with a sudden discontinuity in Strouhal number.

• 대한기계학회논문집B
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• 제20권10호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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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.

• Journal of Advanced Marine Engineering and Technology
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• 제14권1호
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• pp.62-71
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• 1990

Two-dimensional turbulent wake flow past a rectangular cylinder is investigated experimentally by using the linearized constant temperature hot-wire anemometer. Some of turbulent characteristics are obtained at the range of X=6B-500B downstream from the cylinder and the Reynolds number range is 500-2800. For the statistical treatment, autocorrelation coefficient, probability density function and power spectral density function are obtained by using the signal analyzer. It is clear that coherent structure of strong periodic eddies exists to the position of 20B downstream from the cylinder, and its feature is similar to round type as nearer to the cylinder while it is stretched longitudinally along with flow direction as the distance from the cylinder is increased to downstream.

• 수산해양기술연구
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• 제28권2호
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• pp.157-163
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• 1992

In this paper, the relationship between static pressure recovery and turbulent energy was presented in case of swirling flows into a conical diffuser. The distributions of turbulent energy in a diffuser sectional area were measured by a hot wire anemometer. The following conclusion can be drawn from the experiment. Diffuser loss is constituted by a dynamic pressure loss and total pressure loss. The static pressure recovery depends strongly on the total pressure loss. The static pressure recovery depends strongly on the total pressure loss, and the turbulent energy varies inversely as the static pressure recovery coefficient.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.643-651
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• 1998

Turbulent unsteady flows in the entrance region of a square duct are investigated with a hot-wire anemometer system. The velocity waveforms the mean and turbulence components of the axial velocity and the entrance length are obtained as a major characteristics of the developing turbulent unsteady flows. An inviscid flow theory is presented to describe the developing axial mean velocity profiles. A good agreement is seen between the measured and theoretically predicted values. The propagation of turbulence generated near the entrance of the square duct is satisfactorily approximated by an empirical correlation of the propagation of turbulence proposed so far. The local turbulence intensi-ty is found to be a little smaller in the accelerating phase than in the decelerating phase. The entrance length is about 60 times as large the hydraulic diameter.

• 대한기계학회논문집B
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• 제25권8호
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• pp.1077-1086
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• 2001

An experimental study is performed to investigate the characteristics of vortex shedding behind a circular cylinder with serrated fins using hot-wire anemometer. Strouhal numbers which are calculated using outer diameter of a circular cylinder with serrated fins are higher than that of a circular cylinder. Fin thickness and pitch are closely related with vortex shedding frequency and play increasing or decreasing vortex shedding after transient Reynolds number. Strouhal numbers using effective diameters which are proposed in this paper agree with that of a circular cylinder. After transient Reynolds number, a trend of Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter.