The present aim is to reveal the flow past a pipe which is immersed parallel to the mainstream at high Reynolds numbers.In a wind tunnel, we Chews carry out (1) base-pressure measurements, (2) velocity-fluctuation measurements using a hot-wire anemometer and (3) flow visualisations by a smoke-wire method with PIV analyses, where we take consecutive picutures using a high-speed camcorder to obtain quantitative flow-field information such as velocity vector and vorticity.The tested parameter ranges are as follows: Re = 2.0×103 - 1.
3×104, d/t = 4.0 - 10.0 and l/t = 1.0 - 10.
0, where Re, d, t and l are the Reynolds number, mean diameter, thickness and length of the pipe, respectively.As a result, the Re effects are negligible.The base-suction coefficient -Cpb monotonically decreases with decreasing d/t, or with increasing l/t.We propose a unified formula to predict -Cpb, which are consistent with both a two-dimensional prism and a rod for l/t < 4.
0 in addition to a ring.In contrast, the Strouhal number St almost coincides with that for a two-dimensional prism at any l/t, if we can detected any dominant frequencies.In addition, we conduct flow visualisations, and reveal the effects upon axisymmetry of wake.Finally, we classify the flow into three modes based on both Hand-Hammered Dish periodicity and axisymmetry.
Such a modal classification reveals that the enhancement of flow's irregularity corresponds to the decrease of -Cpb.