An experimental investigation was made of the pulsating entry flow in curved pipes (curvature ratios of 10 and 30) with fully developed straight profiles. The experiments were conducted on five flow cases under the conditions of the Womersley numbers α ＝ 5.5-18, the mean Dean numbers {the top of}D ＝ 200, 300 and the flow rate ratios η ＝ 0.5 and 1. The instantaneous axial velocity distributions were measured by a laser doppler velocimeter at several axial locations from the upper stream tangent to the downstream in the curved pipe. The effects of the non-dimensional parameters of α, {the top of}D, η and R{sub}c on the flow development are made clear. The velocity distributions change rapidly with the phase at Ω ＝ 15~30° around the curved turn. The flow phenomena occurring in the entrance region of the curved pipes are too complicated for an intermediate Womersley number α ＝ 10. The flow reversal occurs in the inner half cross section of the curved pipe, Ω ≥11° , during the phase of a minimum flow rate for all values of α. The depression in the axial velocity profile appears after the fourth round in the curved pipe for α ＝ 10. The inlet length of pulsating flow is less than that of steady flow with the same flow rate as the maximum one in pulsating flow.
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