| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 103 === There are two different analyses for turbulent flow quantities, namely, temporal and spatial correlations. Two-dimensional velocity information of the turbulent flow over an axisymmetric cylinder in a downward vertical wind tunnel will be measured using both the cross-type hot-wire and the split-type hot-film anemometry as well as the particle image velocimetry (PIV) in this study. The hot-wire and hot-film anemometry are of intrusive, point-wise velocity anemometry and are capable of measuring the temporal velocity information. In contrast, the PIV is of non-intrusive, planar velocity anemometry and is capable of measuring the spatial velocity information. Comparison of the measured turbulent flow quantities over the cylinder among these three velocity anemometry will be made. Determination of the wake width can be accurately made by means of the sectional distribution of either flatness factor on shear-induced vorticity. The flatness factor is a fourth-order temporal statistics of turbulence and will be calculated using the data measured with the cross-type hot-wire anemometry, while the shear-induced vorticity is regarded with the spatial derivatives of velocity and will be calculated using the data measured with the PIV. Finally, the merits and defects of the employed three velocity anemometry on the measurements of turbulent flow quantities will be discussed.
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