遷移域をもつ軸対称自由噴流Ｉ : 円管噴流の平均速度についての実験

概要

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A free jet of air was issued from a long circular tube into a reservoir of motionless air. By changing the efflux speed of the jet, the smoke observation and the titled measurement by using a small Pitot-tube were carried out in the range of Reynolds number, based on the tube diameter and the efflux velocity, from 1.5×103 to 1.2×10t . The smoke observation has indicated that, in the case of a smaller Reynolds number, the less diffusive region was formed near the jet exit before the jet spread downstream, and the smaller Reynolds number the longer it grew. In the case of a larger Reynolds number the jet became turbulent. In the case of an intermediate Reynolds number, however, both types were observed simultaneously, which might be peculiar to a jet from a long tube. The comparison between an ordinary turbulent jet and a jet at a smaller Reynolds number has shown that the latter spread more rapidly than the former in the transition region which was downstream to the less diffusive region. The penetration length, defined as the axial distance to the point at the onehalf velocity of the efflux one, increased slightly as the Reynolds number of the turbulent jet increased.
信州大学工学部の論文
1973-12-25