泵站进水系统竖直进口空气吸入涡不稳定特性研究OA

Air entrained into the pump intake system by pump suction can generate a locally coherent air-core vortex connecting the free surface to the pipe intake.The air-core vortex is one primary adverse factor affecting the opera-tional efficiency,safety and stability of pumping stations.This paper employs large-eddy simulation coupled with the CLSVOF interface-tracking technique to numerically investigate the air-core vortex phenomena at vertical hydraulic intakes.The interaction between vortex structures and turbulent flow fields during the air-core vortex formation was analyzed using the turbulent kinetic energy transport equation and proper orthogonal decomposition(POD)method.The results indicate that the evolution of the air-core vortex in vertical hydraulic intakes can be categorized into three distinct stages:V-shaped surface swirl,surface dimple,and coherent air-core vortex.The turbulent kinetic energy distribution exhibits a strong correlation with vortex dynamics.Analyses of the turbulent kinetic energy transport equa-tion reveal that the interaction between the streamwise and spanwise components of fluctuation velocities and their corresponding velocity gradients drives local turbulent kinetic energy production,while turbulent kinetic energy diffu-sion provides an essential energy transport pathway for the evolution of random vortices into an air-core vortex.The POD analyses of the fluctuation velocity and vorticity fields reveal that the first two modes of the fluctuation fields exhibit a pair of vortices with opposite rotating directions,which causes the strength of the air-core vortex to increase on one side while decreasing on the other,thereby inducing a lateral displacement of the vortex core.The instability characteristics and mechanisms of the air-core vortex revealed in this paper enrich the theoretical understanding of such vortices and provide a basis for vortex control measures and the optimal design of pumping station intake systems.