Flow Resistance Characteristics of Pulsating Turbulent Flow Through a 90° Bend

Abstract

The characteristics of flow resistance in a pulsating turbulent flow through a 90° bend with a circular cross-section were investigated. Water was used as the working fluid to investigate a wide range of governing parameters experimentally. The Womersley number α varied from 10 to 50, the mean Reynolds number Re_ta from 7000 to 22000, the oscillatory Reynolds number Re_os from 6000 to 14000 (the flow rate ratio η was 0.3-0.8), and the curvature radius ratios R_c were 2, 4, and 6. The pressure drop between 2d (d: inside diameter) upstream and 4d downstream of the bend was measured and analyzed, assuming a quasi-steady flow. The effects of the non-dimensional flow parameters and curvature radius ratio on the flow resistance characteristics were investigated. The approximate expressions for the time-mean value, amplitude, phase difference from the flow rate variation, and power losses were consistent with the experimental results, and were thus practically useful.