• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.479-484
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• 2000

A Navier-stokes based finite volume method has been developed to analyze an incompressible, steady state, turbulent wall-jet flow. The standard k-e model, the RNG ${\kappa}-{\varepsilon}$ model and their nonlinear counterparts are adopted as a closure relationship. Comparison with the experimental data shows that a linear ${\kappa}-{\varepsilon}$ model performs satisfatorily for two-dimensional wall-jet flows. However, as the flow becomes three dimensional, the linear model fails to predict the spanwise jet growth accurately and the nonlinear model needs to be adopted to capture three-dimensional flow characteristics.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.52-66
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• 1998

An experimental study on the flow characteristics was performed for a two-dimensional turbulent wall attaching offset jet at different oblique angles to a surface. The flow characteristics were investigated by using a split film probe with the modified Stock's calibration method. The jet mean velocity, turbulent intensity, wall static pressure coefficient profiles, and time-averaged reattachment point were measured at the Reynolds number Re (based on the nozzle width, D) ranging from 17700 to 53200, the offset ratio H/D from 2.5 to 10, and the inclined angle .alpha. from 0.deg. C to 40.deg. C. The Correlations between the maximum pressure position, minimum pressure position, and reattachment point and offset ratios, and inclined angles are presented.

• 대한기계학회논문집
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• 제7권4호
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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.

• 대한기계학회논문집
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• 제19권1호
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• pp.219-230
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• 1995

The flow characteristics of a two-dimensional offset jet issuing parallel to a rough wall is experimentally investigated by using a split film probe with the modified Stock's calibration method. The mean velocity and turbulent stresses profiles in the up and down-stream locations of the wall-attachment regions are measured and compared with those of the smooth wall attaching offset jet cases. It is found that the wall-attachment region on the rough wall is wider than on the smooth wall for the same offset height and the jet speed. The position of the maximum velocity point is farther away from the wall than that for the smooth wall case because of the thick wall boundary layer established by the surface roughness. It is concluded that the roughness of the wall accelerates the relaxation process to a redeveloped plane wall jet and produces a quite different turbulent diffusion behavior especially near the wall from comparing with the smooth plane wall jet turbulence.

• 대한기계학회논문집
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• 제9권6호
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• pp.732-742
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• 1985

본 논문에서는 이 2차원 재부착분류(본문에서는 stepped wall jet라 명명함) 유동장을 재부착상류 부분, 재부착점 근방, 재부착 이후의 재발전 벽면분류 지역의 세 영역으로 구분하여 재부착 길이, 평균속도, 벽면정압을 측정하고 on-line에 의한 디지 틀 데이터 처리기법을 이용하여 난류강도, 레이놀즈 전단응력, 속도의 3승적(triple velocity product), integral length scale, Taylor's microscale 등을 실험적으로 구 하여 재부착 상류 부분에서는 자유분류와 비교하고, 재부착 이후에서는 2차원 벽면분 류와 비교하기로 한다.그리하여 초기 교란을 받는 분류가 벽면에 재부착하여 2차원 벽면분류로 재발전되어 가는 과정에 있어서의 평균 유동장과 급격한 변화를 갖는 난류 특성을 상세히 조사하여, 보다 일반적으로 적용될 수 있는 난류모델을 개발함에 있어 서 실험적인 자료를 제공하고자 한다. Fig. 1은 본 실험의 유동장에 대한 개약도를 보여주고 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2804-2809
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• 2008

Experimental results and numerical computations were conducted to investigate the effect of the confined wall on the flow and heat transfer characteristics for a two-dimensional impinging jet. Experimental results and Numerical solutions were obtained by using the particle image velocimetry and the commercial CFD code (CFX 11), respectively. The parameters studied were jet Reynolds number (Re=5,000), conditions of confined wall (unventilate), nozzle to plate spacings ($H/W=1{\sim}16$), and nozzle to nozzle spacing (S/W=6). Experimental and numerical results were agreed well with each other. The maximum heat transfer point was found variation of nozzle to plate spacings.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1121-1136
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• 2002

The flow characteristics of film coolant issuing into turbulent boundary layer developing on a convex surface have been investigated by means of flow visualization and three-dimensional velocity measurement. The Schlieren optical system with a spark light source was adopted to visualize the jet trajectory injected at 35° and 90° inclination angles. A five-hole directional pressure probe was used to measure three-dimensional mean velocity components at the injection angle of 35°. Flow visualization shows that at the 90° injection, the jet flow is greatly changed near the jet exit due to strong interaction with the crossflow. On the other hand, the balance between radial pressure gradient and centrifugal force plays an important role to govern the jet flow at the 35° injection. The velocity measurement shows that at a velocity ratio of 0.5, the curvature stabilizes downstream flow, which results in weakening of the bound vortex structure. However, the injectant flow is separated from the convex wall gradually, and the bound vortex maintains its structure far downstream at a velocity ratio of 1.98 with two pairs of counter rotating vortices.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.986-991
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• 2003

A turbulent wake generated by a cylinder in nozzle contraction affects to the jet flow characteristics. In this study, a computational work to investigate the effect of the turbulent wake on two-dimensional subsonic jet was carried out with three different kinds of nozzle. Computations are applied to the two-dimensional unsteady, Navier-Stokes equations. Several kinds of turbulent models and wall functions are employed to validate the computational predictions. It was known that the wake flow enhanced the spread of the jet flow, compared with no wake flow condition. It was also found that the jet core is shortened by the wake flow developed from a control cylinder.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3304-3312
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• 1996

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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.514-519
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• 2000

Recently a considerable interest is being concentrated on industrial applications of supersonic Coanda wall jets, but the flow physics are not still understood well. It is of practical importance to evaluate the effectiveness of supersonic Coanda wall jet devices fer such industrial purposes. In the present work, experiments and computations were performed to Set a better understanding of the supersonic Coanda jet physics. The experiments were made using a small blow-down wind tunnel. The operating pressure ratio and the Coanda surface configuration were changed to investigate their influences on the wall jet flows. Two-dimensional Navier-Stokes computations were performed using a TVD finite volume scheme to effectively capture the important wave structures of supersonic Coanda jet flows. Both experimental and computational results showed several important hysterical features of the supersonic Coanda wall jets; the attachment and detachment of supersonic Coanda jet were strongly dependent on the change processes of the operating pressure ratio and the detailed flow configuration.