Numerical simulation of influence of 90°-bend pipeline geometric shape on local loss coefficient

摘要

Local head loss coefficients of the 90°-bend pipeline for Hydraulic calculation in engineering is empirical value and formula normally experimentally. The values may vary about 2 to 4 times because of the different experimental conditions. This will bring large error for the accurately calculation of the local head loss. Numerical simulation was applied on the pipe with 90° bend that widely used in engineering field. The local head loss coefficients of five types of bends including 1/4 circular arc and 1/4 ellipse with different radius combination were compared. The affected length of local head loss coefficient in the downstream straight sections of the geometric bend was analyzed. Result show that circular arc bend has less local head loss than that of the ellipse and the hydraulic performance of 1/4 circular arc is optimal when fully considering the local head loss at the straight sections of bend downstream. Over 90% local head losses occur at the downstream straight sections, of which affected length is 40 times of the pipe diameter. This fact is independent of the variation of water velocity and the duct diameter.