• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.10-13
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• 2004

The PSP(pressure sensitive paint) technique has recently received a large attention as a new revolutionary optical method to measure absolute pressure distribution on a model surface. The PSP technique can be applied to quantitatively investigate flow structure using a CCD camera and image processing technique. In the static calibration, the luminescent intensity of PSP coatings was measured from 0kPa to 11kPa with 0.5, 1, 2kPa increments. In this study, the low-pressure PSP technique was applied to an oblique impinging jet to measure pressure field variations on the impingement plate with varying angle of an oblique jet. The flow structure over the impingement plate was visualized using a surface tracing method. As a result, the detail pressure field distributions of the oblique low-speed impinging jet were visualized effectively using the PSP technique.

• Journal of Advanced Marine Engineering and Technology
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• 제21권1호
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• pp.37-42
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• 1997

Turbulent flow characteristics of a two - dimensional oblique plate impinging jet(OPIJ) were experimentally investigated. The jet mean velocity and turbulent intensity profIles were also measured along the plate. The jet Reynolds numbers(Re, based on the nozzle width)ranged from 10, 000 to 35, 000, the nozzle - to - plate distance(H/B) from 2 to 16, and the oblique angle (a) from 60 to 90 degree. It has been found that the stagnation point shifted toward the minor flow region as the oblique angle decreases and the position of the stagnation point nearly coin¬cided with that of the maximum turbulent intensity.

• 설비공학논문집
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• 제9권4호
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• pp.427-434
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• 1997

Heat transfer characteristics of a two-dimensional oblique impinging jet were experimentally investigated. The local heat transfer coefficients were measured by a thermochromic liquid crystal. The jet Reynolds number studied was varied from 10000 to 35000, the nozzle-to-plate distance(H/B) from 2 to 16, and the oblique angle($\alpha$) from $60^{\circ}$ to $90^{\circ}$. It was observed that the local Nusselt numbers in the minor flow region were larger than those in the major flow region at the same distance along the plate due to the higher levels in the turbulent intensity caused by more active mixing of the jet flow.

• 설비공학논문집
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• 제12권4호
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• pp.371-380
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• 2000

The turbulent heat transfer from a round oblique impinging jet on a concave surface were experimentally investigated. The transient measurement method using liquid crystal was used in this study. In this measurement, a preheated wall was suddenly exposed to an impinging jet while recording the response of liquid crystals to measure surface temperature. The Reynolds numbers were 11000, 23000 and 50000, nozzle-to-surface distance ratio was from 2 to 10 and the surface angles were a =$0^{\circ}\;15^{\circ},\;30^{\circ}and\;40^{\circ}$. Correlations of the stagnation point Nusselt numbers with Reynolds number, jet-to-surface distance ratio and dimensionless surface angle, which account for the surface inclined angle, are presented. The maximum Nusselt numbers, in this experiment, occurred in the direction of upstream. The displacement of the maximum Nusselt number from the stagnation point increases with increasing surface angle or decreasing nozzle-to-surface distance. In this experiment, the maximum displacement is about 0.7 times of the jet nozzle diameter when surface curvature, D/d is 10.

• 대한기계학회논문집B
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• 제26권7호
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• pp.1031-1038
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• 2002

The pressure sensitive paint (PSP) has recently received a considerable attention in the fields of aerodynamics and fluid mechanics as a new revolutionary optical technique to measure pressure fields on a body surface. In this study, the feasibility and effectiveness of the PSP pressure field measurement technique have been investigated experimentally. Seven different PSP formulations including two porphyrins(PtOEP and PtTFPP) and four polymers(Polystyrene, cellulous acetate butyrate, GP-197 and Silicon-708) were tested to check the performance and characteristics of each combination. The static calibration of each PSP formulation was carried out in a constant-pressure chamber. The PSP technique was applied to an oblique impinging jet flow to measure variation of pressure field on the impinging plate at on oblique jet angle of ${\theta}=60^{\circ}$. Pressure field images were captured by an 12bit intensified CCD(ICCD, $1K{\times}1K$)camera. As a result, the dynamic response of PSP depends on the oxygen permeability of polymer and the photochemical interaction between luminophore and polymer as well as the reaction of luminophore itself. The reaction of luminophore was changed by employing different polymers. In conclusion, Among 7 PSP formulation tested, the combination of PtTFPP and cellulous acetate butyrate show the best performance. In addition, the detail pressure field of an oblique high-speed impinging jet was measured effectively using the PSP technique.

• 설비공학논문집
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• 제10권3호
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• pp.324-333
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• 1998

Measurements of the local heat transfer coefficients on a hemispherically concave surface with a round oblique impinging jet were made. The liquid crystal transient method was used for these measurements. This method, which is a variation of the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystal for the surface temperature measurements. The Reynolds number used was 23,000 and the nozzle -to -jet distance was L/d=2, 4, 6, 8 and 10 and the jet angle was $\alpha$=0$^{\circ}$, 15$^{\circ}$, 30$^{\circ}$and 40$^{\circ}$. In the experiment, the maximum Nusselt number at all region occurred at L/d(equation omitted)6 and Nusselt number decreases as the inclined jet angle increases. For the normal jet the contours of constant Nusselt number are circular and as the jet is inclined closer and closer to the surface the contours become elliptical shape. The decreasing rate of the Nusselt number at X/d＞ 0(upstream) on a surface curvature are higher than those on a flate plate and the decreasing rate of the Nusselt number at X/d ＜0(downstream) on a surface curvature are lower than those on a flate plate. And also, the decreasing rate of local Nusselt number distribution at X/d ＜0(upstream) exhibit lower than with X/d ＜0(downstream) as jet angle increases. The second maximum Nusselt number occurred at long distance from stagnation point as jet angle increases.

• 대한기계학회논문집
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• 제14권3호
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• pp.716-724
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• 1990

본 연구에서는 2차원 경사충돌분류에 대한 실험을 수행하였고, 이 결과를 수] 치해석에 의한 계산치와 비교하였다. 실험에서는 난류특성을 구명하기 위하여 열선 풍속계를 사용해 충돌각의 변화에 따른 평균속도, 각 난류응력성분, 압력등을 측정하 였다.수치해석을 위한 난류모델로는 표준 K-.epsilon.모델을 사용하였다.

• 설비공학논문집
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• 제11권6호
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• pp.846-854
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• 1999

Measurements of the local heat transfer coefficients were made on a hemispherically convex surface with a round oblique impinging jet. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystal for the surface temperature measurements. The Reynolds number used was 23000 and the nozzle-to-surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was $\alpha$=$0^{\circ}\; 15^{\circ}\;30^{\circ}C\; and \;40^{\circ}C$. In the experiment, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit Secondary maxima at $0^{\circ}C\re $\alpha$\re 15^{\circ}C, L/d\le6$ for X/d＜0(upstream) and at $0^{\circ}C\re $\alpha$40^{\circ}C,\;L/d\le4\;and\; at\; 30^{\circ}C\re $\alpha$$\leq$40^{\circ}C,\;L/d\le 6 $for X/d＞0(downstream). The secondary maxima occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. The Y-axis Nusselt number distributions exhibit secondary maxima at Y/d=$\pm$2 for $0^{\circ}C\le a\le30^{\circ}C\; and\; L/d\le4, and \;for\;$\alpha$=40^{\circ}C$and L/d=2. The displacement of the maximum Nusselt number from the stagnation point increases as the jet angle increases or the nozzle-to-surface distance decreases and the maximum distance is about 0.67 times of the nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

• 한국추진공학회지
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• 제21권2호
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• pp.83-93
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• 2017

파형 구조는 배열 충돌제트 하류에서의 횡방향 유동 영향을 줄이기 위해 충돌제트 사이의 파형 속에 사용된 냉각 공기를 유입시키며, 이러한 파형 구조에서의 유동 및 열전달 특성에 대해 수치해석을 수행하였다. 모든 계산은 3차원, 정상상태, 비압축성 유동으로 고려하였으며 ANSYS-CFX 15.0 코드를 사용하였다. 제트 홀에서 평균 Reynolds 수는 10,000이며, Spanwise 단면에서 충돌제트의 경사각도는 $70^{\circ}$, $80^{\circ}$ 및 $90^{\circ}$ 이고, Streamwise 단면에서 충돌제트의 경사각도는 $70^{\circ}$, $90^{\circ}$ 및 $110^{\circ}$ 이다. 본 연구에서는 배열 충돌제트의 경사각도가 파형 구조의 유동 및 열전달 특성에 미치는 영향에 대해 고찰하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.260-267
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• 2001

The objective of this study was to investigate the characteristics of jet flow and heat transfer caused by trapezoid rods array in impinging jet system. In this study, trapezoid rods have been set up in front of flat plate to serve as a turbulence promoter. The bottom width of trapezoid rod was W=4, 8mm and oblique angle were $80^{\circ}$. The space from rods to the heating surface was C=1, 2, 4mm, the pitch between each rods was P=30, 40, 50mm, and the distance from nozzle exit to flat plate was H=100, 500mm. This results were compared with the case without trapezoid rods. As a result, when rods are installed in front of the impinging plate, the acceleration of the jet flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Among test conditions, the heat transfer performance was best for the condition of W=8mm, C=1mm, P=30mm and H/B=10. The maximum heat transfer rate is about 1.9 times larger than that without trapezoid rods.