Research On The Winglet Drag Reduction Mechanisms Based On Wingtip Vortex Physical Characteristics And Interaction

It has long been a focus of drag reduction research of an aircraft which is closely related to its economy and environmental protection.Through the research on laws of the physical characteristics and interaction of wingtip vortex from wing or wingtip device,airplane designers and aerodynamicists can build drag reduction principles which may guide drag reduction design of wingtip devices.Motivated by this For this reason,this paper will research in-depth on the evolution features of wingtip vortex resulted from 3d clean wing and wing installed by wingtip device.The physical characteristics and induced drag generation mechanism are also explored.By this way,the drag reduction mechanism of wingtip device is revealed.The main work and conclusions of this thesis include the following three aspects:(1)The study of evolution characteristics of wingtip vortex and its physical characteristics.From the clean and rectangular wing,through numerical simulation method,the structure characteristics and physical characteristics throughout evolution process of wingtip vortex is explored.Then three formation stages of generation stage,growth stage and wake stage and are founded.By changing Reynolds number,Mach number and Angle of attack of flow conditions,further study on the evolution behavior of wingtip vortex is carried out.The pinch-off mechanism of merged primary during its wake stage is put up with combined with the basic theory of the growth of vortex.In this way,wingtip vortex evolution theory is established.(2)The study of scientific evaluation criteria of induced drag reduction.Based on the instability characteristics of wingtip vortex of M6 wing,for example,the mathematical model of circulation of wake vortex dissipation is put forward and the improvement of current calculation method of the induced drag schemes are also presented.The improved method has a bigger scope when selecting the wake section and reveals the scientific nature if the section of pinch-off location is chosen as integration section.This aspect research can be referred to the unified criteria of induced drag reduction evaluation.(3)The study of drag reduction design principles of the wingtip device.Through the research on the structure characteristics and physical characteristics of wingtip vortex from wingtip device,the universe law of wingtip vortex evolution is sought.Based on this,the drag reduction design guiding principle is summarized.And the scientificity and the rationality of design concept is also validated through installed the other wingtip shape devices.Results show that through accelerating the pinch-off location of merged primary vortex;inhibiting the dimensionless circulation extremum of merged primary vortex and increasing the distance between the integration of the main vortex and corner vortex which is related with the interaction of wingtip vortex when design wingtip drag reduction device,the induced drag can be decreased.