Research On Numerical Simulation Of Turbulent Flow In Hydrodynamic Coupling And Recognition Method Of Three-dimensional Vortex Structure Features

Hydrodynamic coupling is a hydraulic transmission element that relies on fluid to realize energy transmission and conversion.The understanding of unsteady multiscale vortex flow and its complex turbulence phenomenon in hydrodynamic couplings is insufficient.It is not accurate enough to grasp the generation,development and evolution law of the threedimensional vortex field structure in the flow channel.There are still many key scientific problems that need to be solved urgently in the research of flow field theoretical analysis,turbulent flow numerical simulation technology and flow field test measurement method.This paper is based on the interactive research method of turbulent high-precision numerical simulation and flow field visualization test measurement.The turbulence structure evolution law and three-dimensional vortex structure feature recognition method of hydrodynamic coupling are studied in depth.The main research contents are as follows:Firstly,three-dimensional flow channel models of hydrodynamic coupling with different cavity structures are established.Based on the grid partitioning technology and grid independent analysis,the high quality grid model is generated.Research on the construction method of different sublattice turbulence models for large eddy simulation and stress blended eddy simulation models.Different turbulence models are used to simulate the flow field of hydrodynamic coupling with square cavity and peach cavity.The structure evolution characteristics and flow mechanism of the internal turbulence are analyzed.The applicability analysis is carried out for the numerical simulation effect of different turbulence models.Secondly,this paper focuses on the development process of the first,second and third generation vortex structure identification methods.Explore the precise mathematical definition of vortex structure and the clear expression in the physical sense.The threedimensional flow field of hydrodynamic coupling is reconstructed by multi-generation vortex recognition method.The influence of different vortex recognition methods and the selection of reasonable threshold range on the flow field reconstruction effect is analyzed.In-depth comparison and analysis of the three-dimensional vortex structure characteristics of the overall flow field of the hydrodynamic coupling and the fine identification of the details of the threedimensional vortex structure characteristics of the local flow field are carried out.The applicability and reliability of different vortex recognition methods for three-dimensional vortex structure recognition and extraction in hydrodynamic coupling flow field are studied.Finally,in order to verify the accuracy and reliability of the numerical simulation results.Through self-designed and constructed flow field visualization test system.The measurement technology of optical non-contact flow visualization test and the method of fast and high precision flow image calibration are studied.Two-dimensional flow field images of radial section of hydrodynamic coupling under different working conditions are acquired.Image preprocessing algorithm is studied to improve the quality of original image.Detailed and reliable information of velocity field and vorticity field are extracted based on normalized continuous frame image cross-correlation calculation.The numerical simulation results are verified by comparison.Evaluate and proofread the accuracy and reliability of simulation results.