Improved weight-function model of unsteady friction in hydraulic transients
ZHOU Ling1*, LIU Jing1, OU Chuanqi2, QIAN Suping3, LU Kunming4
1. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2. International Center on Small Hydro Power, Hangzhou, Zhejiang 310000, China; 3. Taizhou Water Conservancy Bureau, Taizhou, Jiangsu 225300, China; 4. China Three Gorges Construction Engineering Corporation, Chengdu, Sichuan 610041, China
Abstract：In pressurized water conveyance pipeline system, water hammer phenomenon often occurs due to the opening and closing of valves or improper operation of hydraulic components, thus affecting the normal operation of hydraulic system and even causing dangerous accidents. Therefore, it is of great significance to carry out effective numerical simulation prediction for the above water hammer phenomenon. In the simulation of pipeline hydraulic transient process, the weight-function unsteady friction model proposed by Zielke, which is considered to be the most accurate mathematical model in one-dimensional water hammer simulation, can accurately simulate the pressure fluctuation process. Since the weighting function is related to the historical velocity and acceleration, the velocity value of each step needs to be saved in the model calculation, which occupies a large amount of computer memory. So, the calculation efficiency is low. In order to improve the model′s computational efficiency, this paper tries to use Matlab LSQNONLIN function module to approximately fit the Zielke weighting function with a new function, which is the form of the sum of three exponential functions, gets the coefficients of new approximation weighting function, as well as the new function′s superiority by comparing Zielke weighting function curve and existing improved weighting function curves, as well as the new model′s accuracy and efficiency against experimental data. The results show that the model in this paper improves the calculation efficiency of the weight-function unsteady friction model to some extent.
