Hydraulic calculation for free flow in circular section by iterative method
LU Hong?xing, BA Duo?duo,SONG Song?bai (College of Water Conservancy and Architecture Engineering of Northwest Science and Technology University of Agriculture & Forestry, Yangling 712100,China)
Owing to the fact that the calculation formulas of normal depth and critical depth for free flow in circular section of tunnel and drainage culvert werent expressed by explicit function in hydraulics, the conventional trial and error method and specific hydraulic graphs had to be used in calculating these values. In order to improve this situation, an iteration formulation for calculating these two parameters were derived. The calculation formulas of limiting tunnel diameter and limiting discharge under the condition of the net space area not less than 15% of the total cross section area or the free height not less than 0.4 m, were presented, and the judgment expressions of maximum water depth and discharge with uniform flow were given. The iterative operation was used in the calculation. After examination, the results show that the method has better convergence and higher precision and can be used in practical engineering design.