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단이 진 경사벽면에 부착되는 2차원 평면제트의 열전달 효과에 관한 연구
윤순현,이대희,심재경,송흥복,Yun, Sun-Hyeon,Lee, Dae-Hui,Sim, Jae-Gyeong,Song, Heung-Bok 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.10
Experiments have been conducted to determine the flow and heat transfer characteristics for a two-dimensional turbulent wall attaching offset jet at different oblique angles to a flat surface. The distributions of the wall static pressure coefficient and time-averaged reattachment position for various offset ratios and oblique angles have been measured. The local Nusselt number distributions on the plate surface were also measured using liquid crystal as a temperature indicator. The new hue-capturing technique utilizing a true color image processing system was used to accurately determine the temperature of the liquid crystal. The experiments were carried out at Reynolds number, Re (based on D) of from 7300 to 21,300 with offset ratio, H/D from 2.5 to 10, and oblique angle, .alpha. from 0 deg. to 400 deg..
2차원 채널 충돌제트에서 난류강도의 변화에 대한 유동 및 열전달 특성
윤순현,김동건,김문경,Yoon, Soon Hyun,Kim, Dong Keon,Kim, Moon KyounK 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.6
Experiments were conducted to investigate the effect of the initial turbulent intensity on the flow and heat transfer characteristics for a two-dimensional impinging jet. A square rod was installed at the nozzle exit to increase initial turbulent intensity. A hot wire probe and thermochromic liquid crystal technique were used to measure the turbulent intensity and the surface temperature. All measurements were made over a range of nozzle-to-plate distance from 1 to 10 at Re=20,000. When the rod is not installed, the maximum stagnation point Nusselt number is occurred at H/B=9. A higher initial turbulent intensity enhanced the heat transfer on the surface. A correlation between stagnation point Nusselt number and turbulent intensity are presented.
사각주 후류가 선형터빈익렬의 유동 및 열전달에 미치는 영향에 관한 연구
윤순현,심재경,우창수,이대희,Yoon, Soon Hyun,Sim, Jae Kyung,Woo, Chang Soo,Lee, Dae Hee 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.7
An experimental study Is conducted in a four-vane linear cascade in order to examine the influence of the wake behind rectangular bars on the flow and heat transfer characteristics. 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 are measured using a hot-wire anemometer, and to measure the convective heat transfer coefficients on the blade surface liquid crystal/gold film Intrex technique is used. Each of experimental cases is characterized by the unsteadiness measured at the entrance of the cascade. The wake behind the rectangular bars enhances the turbulent motion of the flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the blade surface increase with increasing unsteadiness.
윤순현,이대희,송흥복,김대성,Yun, Sun-Hyeon,Lee, Dae-Hui,Song, Heung-Bok,Kim, Dae-Seong 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.10
An experimental study on the convective heat transfer characteristics was performed for a two-dimensional wall attaching offset jet(WAOJ). Thermochromic liquid crystal was used to measure the plate wall temperature. The Nusselt number was measured for Reynolds numbers from 6, 500 to 39, 000, and the offset ratios from 0.5 to 15. The maximum Nusselt number point coincides with the time-averaged reattachment point and Nusselt number decreases monotonically after the jet reattaches on the wall. In the recirculation region Nusselt number minimize near the upstream corner and then increases as X/D decreases to vanishes. This suggests the existence of secondary vortices, causing an additional mixing of the flow in the corner. The correlations between the local Nusselt number and Reynolds number, Re, offset ratio, H/D, and streamwise distance, X/D are presented.
윤순현,류원택,김동건,김대성,김귀순,Yun, Sun-Hyeon,Ryu, Won-Taek,Kim, Dong-Geon,Kim, Dae-Seong,Kim, Gwi-Sun 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.3
The effects of hole expansion angle and the arrangement of nozzles on a film cooling system for a turbine-blade-shaped surface were experimentally investigated. Liquid crystal with flue-temperature correlation and an image processing system were employed to evaluate surface temperature. Distributions of cooling effectiveness were then presented to figure out the change of heat transfer characteristics with different geometric conditions of cooling-holes. It was found thats the averaged cooling efficiency on the suction surface was maximum with 10 degree of the cooling hole expansion angle. It was also shown that the averaged cooling efficiency on the pressure surface and the averaged cooling efficiency for dual array case were not affected by the hole expansion angle.
윤순현,엄윤섭,정명균 대한기계학회 1988 대한기계학회논문집 Vol.12 No.4
본 연구에서는 부정숙 등에 의한 실험결과를 토대로 하여, 단이 진 2차원 벽 면분류에 대한 수치해석으로 표준 K-.epsilon.모델과 LRM 그리고 PAM을 적용하고, upwind 및 skew-upwind scheme을 적용하여 그 결과를 검토하고자 한다. A two-dimensional stepped wall jet was numerically investigated by applying three different models : One is the standard k-.epsilon. and the other is the modified k-.epsilon. model which takes account of the streamline curvature effect by modifying the Reynolds shear stress and a source term in the dissipation equation, and a third is curvature dependent third-order correlation model. In order to test the influences of the numerical result, both the upwind scheme and the skew-upwind scheme were sued for the computations. By comparing the numerical results with available experiments, it was found that the modified k-.epsilon. model gives best overall prediction accuracy only when the numerical diffusion is eliminated by using the skew-upwind scheme. The numerical scheme was found to have more pronounced effect on the accuracy of the turbulence computation than the turbulence models.