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尹焞絃,夫禎淑,徐鎬澤 부산대학교 공과대학 1987 硏究報告 Vol.33 No.-
Numerical calculations for the two dimensional reattachment jet flow fields having offset ratio 2.5 were done by skew upwind scheme method and compared with experiments. The standard and modified k-ε models are used as turbulence models and the modified one is considered the streamline curvature effect and preferential dissipation. In experiments, the nozzle exit velocity is 30m/s and the turbulent intensity is 0.2% at the nozzle exit. The reattachment length in the calculated results by the modified k-ε model has 3% error with the experiment. And the modified k-εmodel is better than the standard one for prediction the mean velocity field and static pressure field in this case.
金炅天,尹焞炫 부산대학교 공과대학 1986 硏究報告 Vol.31 No.-
Measurements of mean velocity and turbulence characteristics have been made in a separated, reattached and then redeveloping turbulent shear layer behind a two-dimensional surface-mounted thin block obstacle. Static pressure profiles have also been measured in the whole flow field. In the upstream of the reattachment zone, the extra rate of strain ∂V/∂X and the static pressure both vary significantly across the separated bubble zone due to a stabilizing streamline curvature. Near the reattachment zone, the Reynolds stresses and the turbulent kinetic energy are found to decrease because of the large eddy distortions by the presence of the solid wall boundary. After the reattachment point, transverse change of the integral length scale is more rapid than the length scale growth in the longitudinal direction.
夫禎淑,權大甲,尹焞鉉,李祥秀,李大吉 부산대학교 공과대학 1982 硏究報告 Vol.23 No.-
Two dimensional turbulent jet exhausting into a stationary atmosphere was studied experimentally by use of the linearized constant-temperature hot-wire anemometer. It was established that the jet was truly self-preserving about 40 slot widths, and the measurements were made up to 160 slot widths downstream of the nozzle. In order to get the two dimensional jet, the cubic equation suggested by Morel was used for the contraction curve of the nozzle. The uniformity of the jet velocity was well achieved and the turbulence intensities were low at the nozzle exit. It shows that the spreading rate was 0.094, and the turbulence intensities at the similarity region were u'/U_(m)=0.21, v'/U_(m)=0.18 and w'/U_(m)=0.16 respectively. When the nozzle exit velocity was vaired, it appeared that the starting point of the similarity region was moved to the nozzle for the low Reynolds number. The ratio of the entrance flow velocity to the center line velocity of the jet was about 0.07.
夫禎淑,權大甲,尹焞鉉 부산대학교 공과대학 1981 硏究報告 Vol.22 No.-
The loss characteristics of several types of orifices are studied experimentally. They include sharpedged, qradrant-edged, square-edged orifices. The shape of K versus R curves is analyzed for the different orifices. Interpolating the experimental results, the loss coefficient values are presented for three nominal β ratios of 0.2, 0.4 and 0.6. A relative comparison of the loss characteristics of the different orifices is made. The effects of β ratio and orifice bevel angle are considered.