Department of Chemical Engineering, Fuzhou University, Fuzhou 350002, China
Funding project: 福建省教育厅科技基金资助项目(JB03048)
Received: 2005-07-18
Available online: 2006-06-20
Abstract
The friction factor for the turbulent flow in pipes is the binary nonlinear function of Reynolds number and relative roughness. Calculating friction factor by implicit Colebrook equation have to use iterative algorithm, which is discommodious.The intelligent fitting method for binary nonlinear polynomials was presented in order to obtain a high precise and simple form explicit equation for calculating the friction factor. The binary nonlinear polynomial was firstly transformed into multivariate linear polynomials, and the least squares standard matrix was established. Then the number, the form, the index and the coefficient of polynomials term were searched to obtain the optimum function by genetic algorithms combined with matrix method. Fitting the data calculated by Colebrook equation with the above method, a new explicit equation for calculating the friction factor for the turbulent flow in pipes was obtained. The new equation can reproduce the Colebrook equation with average deviation of 0.5% and the maximum deviation of 1.8% in the range of Reynolds number being 3 000≤Re≤108 and relative roughness being 0≤e/d≤0.05,and it has an average deviation of 2.3 % to the experimental data. The new equation has the advantages such as simple form, high precise, wide range of application, and can be simplified to the equation for calculating the friction factor in the range of smooth pipe and the rough region easily.
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