FTLE evaluation method for mixing ability of jet pump
ZHAO Kai1, CHENG Huaiyu1, LONG Xinping2, JI Bin1, LAI Xu1
1. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, Hubei 430072, China; 2. Hubei Key Laboratory of Waterjet Theory and New Technology, Wuhan Hubei, 430072, China
Abstract：In order to study the spatial distribution characteristics and influencing factors of jet pump mixing capacity, the mixing capacity of jet pump was evaluated and analyzed by using finite time Lyapunov exponent(FTLE). Firstly, the time and space discrete velocity vector field in the computational domain is obtained by numerical simulation. Then, using particle tracking technology and virtual neighbor node FTLE solution method, the ftle solution program is developed; finally, the mixing capacity of a typical jet pump is deeply analyzed based on FTLE field. The results show that the mixing capacity of jet pump in stable operation remains relatively stable and basically does not change with time; the average mixing capacity in the axial direction of the jet pump first increases with the diffusion of the high mixing capacity area of the shear layer, and then decreases with the attenuation of the overall mi-xing capacity; under the operating condition of larger flow ratio, although the jet pump can enter the state with strong mixing capacity in advance, the length of the watershed with continuous high-intensity mixing capacity becomes shorter. Considering the intensity of mixing capacity and the length of high-intensity mixing capacity watershed, the mixing capacity of jet pump can be evaluated more accurately.
