Study On Scalar Mixing Characteristics And Hybrid Enhancement Technique For Supersonic Turbulent Mixed Layer

Based on the study of fuel-rich gas and supersonic inlets inside DCR,the physical model of supersonic turbulent mixing layer is builded to simulate specific engineering problems in this dissertation.Using the technique of LES,NPLS and PIV,passive mixing enhancement mechanis m with different flow parameters and trailing edge structure is studied in the dissertation.First of al,the influence of different flow parameters(e.g.Reynolds number,convective Mach number)is studied on momentum and scalar characteristics of supersonic mixing layer.The study of momentum characteristics proves that Reynolds number mainly makes contribution to completely mixed section,while the increase of convective Mach number will influence the whole flow field.On the other hand,in terms of scalar characteristics,self-similarity is found.Differ e nt from unimodal distribution of momentum,scalar fluctuation and longitudinal pulse output show up in the form of bimodal distribution.What's more,with the change of flow parameters,bimodal distribution will gradually turn into unimodal mode.Secondly,trailing edge test piece is designed to make the research of the passive enhanceme nt technique.These pieces have a thickness of 1mm,in the shape of sawtooth with different space width.With the help of NPLS observation system,accurate flow structures are gotten.At the same time,using handling method of image enhancement,edge detection,cross-correlation detection and processing of the fractal dimension,the evolution of space and time of mixing layer is studied in this dissertation.Referring to the space development,different structure of serrated trailing edge is successfully observed.On the other hand,in terms of time development,using cross-correlatio n techniques,the mixture of laminar flow field is calculated the speed of large scale structure,large scale structure of the whole shows the fast motion,slow change of flow characteristics.In addition,on the issues of law found in the passive hybrid enhanced experiments,this dissertation reveals the serrated trailing edge mixing enhancement mechanism by the threedimensional large eddy simulation.It is thought that serrated trailing edge structure can induced flow vortex,to present a sine distribution in wingwise,with wave crest in the prong,peak valley in the alveolus,which fits the phenomena observed in the experiment wel.In addition,space width determines the forms of flow vortex.Finally,a rectangular wave lobed streamwise vortex generator is designed to study the vortex evolution characteristics and scalar mixing characteristics.Study found that the trailing edge structure induces flow vortex,which can make fluid on both sides suck into the vortex core,greatly expands the mixed area.As a result of the flow to the vortex shear effect,large scale vortex structure quickly breaks into small pieces,increasing the contact area of two fluid,which leads to the increase of scalar's mixing efficiency.