Properties in a Relaminarizing Turbulent Boundary Layer under a Favorable Pressure Gradient.

概要

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Behavior of the turbulent boundary layer on a flat plate in a relaminarizing process with flow acceleration due to a contraction is experimentally investigated. First of all, it was confirmed that the characteristic properties in the boundary layer and the variation of the velocity distribution qualitatively coincide with the tendency of previous studies. Then, some statistical properties were measured and the turbulent structure was examined in detail. In the relaminarizing process, low amplitude fluctuating portions appear intermittently in the velocity oscillogram. In the retransitional process an irregular velocity fluctuation appears intermittently ; then it grows and always becomes turbulent. The turbulent energy dissipation decreases in the relaminarizing process and increases in the retransitional process. In the distributions of probability density function and skewness factor, motions in which the fluctuating velocity largely takes negative values are observed. In the relaminarizing process, vorticity increases in the large eddy and decreases in the small eddy. The small eddies become coarse, and the contribution from the high wave number decreases.
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