• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.155-158
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• 2005

The spray characteristics of liquid jet minted in subsonic cross-flow were investigated numerically and experimentally. The behaviors of column, penetration and breakup of plain liquid jet in non-swirling cross-flow of air have been studied. Numerical and physical models are based on a modified KIVAII code. The primary atomization is represented by a wave model based on the KH(Kelvin-Helmholtz) instability that is generated by a high interface relative velocity between the liquid and gas flows. CCD camera has been utilized in oder to capture the spray trajectory. The nozzle diameter was 0.5 mm and its L/D ratios were between 1 and 5. Numerical and experimental results indicate that the breakup point is delayed by increasing gas momentum ratio, the penetration decreases by increasing Weber number and the turbulent or nonturbulent liquid jet is obtained at different L/D ratio.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1149-1154
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• 2008

The present study investigates the heat transfer characteristics on concave surface with array impinging jet and fin arrangement. The heat transfer coefficients was measured by TLC method. The Reynolds number based on jet hole diameter is 10,000 and hole diameter-to-plate distance ratio (H/d) is fixed at 2. The rectangular fins are installed in the curved channel and the width of fin varies from 1d to 3d. Without fins, the averaged heat transfer coefficients decreases as moves downstream region. While, the rectangular fins block the crossflow and higher heat transfer rates were observed compared to smooth channel.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.2
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• pp.137-145
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• 1992

coefficient precisely, experiments were carried out in three categories which contain the regime of (1) constant wire temperature (2) constant fluid temperature (3) constant temperature difference between wire and fluid. Measurements were made with electrically heated circular tungsten wire placed normal to air stream at the exit of jet. Heat transfer coefficient was increased with wire temperature increasing and decreased by fluid temperaure increasing and was not changed with varying both temperature if their difference were kept constant.

• Journal of Aerospace System Engineering
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• v.13 no.6
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• pp.9-16
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• 2019

The experiment on the liquid jet in crossflow in supersonic BFS (backward-facing step) flow was conducted to investigate the mixing characteristics. The working fluids are nitrogen and water. The shadow graph technique was used to visualize the flow field. Images captured by the high-speed camera were applied to analyze the flow phenomena. The liquid jet was injected at the re-circulation zone created by the supersonic jet flow. Experimental conditions are defined based on the pressure of the nitrogen gas chamber and pressurized liquid tank. In respective cases, the penetration depth of liquid jet and location of the Mach disc were observed to be proportional to the momentum ratio of gas and liquid jets.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.2
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• pp.24-32
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• 2008

A non-reacting experimental study on a normal injection into a Mach 1.92 crossflow which flows over various geometries(flat plate, small cavity, large cavity) was carried out to investigate the effect of the momentum flux ratio(J). The aft ramp of the cavity advances the increase of the penetration height and the strong two-dimensional shock from recompression region mainly affects the shock structure and mixing layer at the downstream flow. As flow runs downward, the transverse penetration height increases with increasing J(J = 0.9, 1.7, 3.4). However, above some critical ratio, jet penetration height growth with increasing J is not appeared in flow-field. Large scale cavity has a good mixing efficiency but it increases the drag loss in the combustor.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.2
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• pp.15-22
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• 2003

Computational study using the 2-dimensional, compressible, Navier-Stokes equations is performed to predict the discharge coefficient of air flow through a film-cooling hole. In order to investigate the effect of internal/external flows on discharge coefficient, the present computational results which are obtained for three flow cases, only external flow, only internal flow, and no flow, are compared with experimental ones. It is found that the computational results predict the discharge coefficient of the film-cooling hole in a reasonable accuracy and the external crossflow reduces the discharge coefficient, while the internal crossflow increases the discharge coefficient in a range of momentum flux ratio $I_{c-jet}$ > 1 due to the total pressure loss and boundary layer effect.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.6
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• pp.466-473
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• 2011

The buoyancy and initial momentum fluxes make near-field dominated by buoyant jet when thermal discharge releases underwater. In order to estimate prediction capabilities of those near-field phenomena, non-hydrostatic RANS applied CFD(Computational Fluid Dynamic) model was used. Condition of model was composed based on past laboratory experiments. Numerical simulations carried out for the horizontal buoyant jet in the stagnant flow and vertical buoyant jet into crossflow. The results of simulation are compared with the terms of trajectory and dilution rate of laboratory experiments and analytic model(CorJET) results. CFD model showed a good agreement with them. CFD model can be appropriate for assessment of submerged thermal discharge effect because CFD model can resolve the limitations of near-field analytic model and far-field quasi 3D hydrodynamic model. The accuracy and capability of the CFD model is reviewed in this study. If the computational efficiency get improved, CFD model can be widely applied for simulation of transport and diffusion of submerged thermal discharge.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.905-911
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• 2017

Effects of injector position and momentum flux ratio on a vertical jet in a cross flow field were studied qualitatively and shown by using air and water. The experiment was carried out by fixing the momentum flux ratio and varying the position of the injector hole. Conversely, the injector hole position was fixed and the momentum flux ratio was varied. Image visualization was performed by a Shadowgraph technique using a high speed camera. The visualized images were compared for finding differences in spraying through Density Gradient Magnitude Image. It is observed that as the x/d of the apparatus increased the jet break up height decreases and the spray angle also decreases. When x/d is 0, the spray reaches the floor and ceiling at any momentum flux ratio.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.88-96
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• 2018

Effects of injector position and momentum flux ratio on a vertical jet in a cross-flow field are qualitatively studied and displayed using air and water. The position of the injector hole and the momentum flux ratio is changed and image visualization is performed using a shadowgraph technique and a high-speed camera. The visualized images are compared to find differences in spraying using density gradient magnitude image. It is observed that, as the x/d of the apparatus increases, the jet break-up height decreases. When x/d is 0, the spray reaches the bottom and ceiling at any momentum flux ratio.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.6
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• pp.708-716
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• 1988

Local heat transfer coefficients were measured on semi-cylinders on which a circular water jet impinged in crossflow. The ratio of the semi-cylinder's diameter and the nozzle outlet diameter were varied parametrically, as were the Reynolds number and the supplementary water heights. The measurements showed that the circumferential distribution of the heat transfer coefficient peaked at the stagnation point. For a fixed supplementary water height, the peak heat transfer coefficient was not depend on the curvature of test specimen(d/D). Optimum height of supplementary water which brought about the augmentation of heat transfer at the stagnation point was S/D=1. The Nusselt number decreased as the circumferential distance or angle increased. The circumferential distribution of dimensionless heat transfer (Nu/Nus) was independent of d/D ($d/D{\geq}8.33$), but for the d/D<8.33, it was depended on d/D. At a fixed angle of specimen, dimensionless heat transfer (Nu/Nus) decreased as the ratio d/D increased. The extent of the decrease between d/D=6.67 and 8.33 was markedly greater than that between d/D=8.33 and 10, or d/D=10 and 11.67.