高レイノルズ数域における曲率の強いエルボ内流れのLDV計測(流体工学,流体機械)

概要

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Pressure measurements, laser Doppler velocimetry (LDV) and flow visualization were carried out for a 90° elbow with a curvature that coincides with the pipe inside diameter in order to clalify the structure of a fluid fluctuation occuring in the bend. Results of pressure measurements show that the value of the pressure loss occurring in the elbow coincides with the conventional empirical formula with a turbulent boundary layer. This agreement is applicable to the case that Reynolds number is greater than 50000. Detailed results of LDV measurement for Reynolds number of 50000 is shown. Frequency analyses of axial velocities indicate that two kinds of flow fluctuations exist in the present elbow. One is the fluctuation with approximate Strohal number (based on a pipe inner diameter and a bulk velocity) of 1.0 occurring in a shear flow region. The other is with approximate Strouhal number of 0.5 occurring in the separated and its downstream regions. These fluctuations were also observed by flow visualization.
2010-05-25