Cycle-to-Cycle Variation Analysis Of Experiments And Simulation Of In-Cylinder Flow Field Based On POD

Due to the high turbulence intensity and the cycle-to-cycle variation of the in-cylinder flow field,it is critical to conduct an analysis on such variation for the experiments and simulation.Data on the in-cylinder flow field of an optical engine are collected via high-speed particle image velocity measurement and large eddy simulation.These results are used to calibrate the engine model.By analyzing the fluctuation of the coefficient of the main modes,this thesis elaborates on differences in characteristics of the flow field that contains the most energy and of local small eddies.It also presents an innovative method to calibrate the simulation of the in-cylinder flow field based on the modal correlation coefficient,which shows the weight of the main POD modes of experiments and simulations in the mixed POD modes.This leads to a clear comparison between the results of experiments and of simulations,contributing to the comprehensive calibration of the flow field.Due to the regularity and regional characteristics of Delaunay triangulation,as well as the complexity of in-cylinder flow fields and the irregular spatial distribution of dots,this algorithm is used in flow field interpolation.With the characteristics that in-cylinder tumble and swirl planes show in flow fields,an innovative method based on ROD is introduced,which is verified in the experimental result of the flow field plane.This enables the interpolation and 3D reconstruction of experimental flow fields.