Research On Aerodynamic Shape Design Technology Of Aircraft Based On The Prediction Of Transition Point Of Separation Flow

Two different flow states are discovered by a British scientist named Renault in 1883.They are laminar flow and turbulent flow.Since then,the study of complex flow characteristics has been started.With the development of hydrodynamics,transition and separation have become one of the most important research topics in the last century.To a great extent,transition and separation are main uncertain sources of aircraft design.In daily life,the phenomenon of transition and separation are very common,but the existence of randomness and uncertainty and lack of accurate definition of the necessary logical level make the development of this theory not yet mature.Therefore,in the related design of fluid machinery,more complex and cumbersome semi-empirical models are usually adopted,such as some common dimensionless parameters,such as Reynolds number,Mach number,and Sherwood number.Although these parameters are widely used in various fields of engineering,there are still big problems in their prediction accuracy,which greatly restricts the development of the aviation industry.In this thesis,the external aerodynamics of the wing is studied from the aspect of numerical implementation.Based on the application of boundary integral equation method,the distributed kinematics and dynamics characteristics of airfoil group motion profile system and viscous incompressible fluid flow are studied.Some results of the calculation experiments are also presented.The aerodynamic distribution of viscous incompressible fluid in the control region is determined.However,this method does not show the mathematical and physical significance of the separation and transition.And it cannot accurately calculate its location.In order to predict the location of separation and transition better,the separation and transition are studied by rational mechanics method.Using Euler description,the velocity of fluid at a certain point in space can be regarded as instantaneous velocity,and the instantaneous velocity minus the time average velocity is the wave velocity.The concept of excited state is defined by the generation of wave velocity.Transition and separation are defined by phenomenological properties of excited states and pulsating velocity.Using the idea of superposition state in quantum mechanics,the generation of excited state is analyzed mathematically.Finally,the necessary and sufficient conditions of transition and separation are studied and compared with the experimental results of separation and transition on the upper part of the airfoil.The accuracy of the prediction results is within1%.The nonlinear separation and transition point prediction of aircraft are developed and realized by the means of theoretical analysis,application method research,applicable conditions,engineering design and verification.In mathematics,it provides help for the exact solution of Navier Stokes equation.And it indirectly proves the smooth solution of Navier Stokes equation under extreme conditions.In physics,the mathematical model of transition and separation is established by describing the phenomena of transition and separation.In engineering,it provides a new design method for aircraft design.