| The wing is one of the key components of the airplane,and increasing lift and reducing drag are critical to the optimization design of the wing.There are two technical difficulties in the researches of increasing lift and reducing drag,one is to resolve the problem of the deteriorated lift/drag features caused by flow separation at low speed and shock wave at high speed,the other is how to improve the deteriorated lift/drag features at the non-design conditions.Flow control technology means that the local flow around the moving body is controlled to change the moving body’s force or moving status.Especially,flow control technology based on the minisize controller is a hot topic in the field of fluid dynamics and it is an important recreation source for the future aircraft.In despite of the trinity effectiveness combined with parameter impacts,flow control mechanisms and application effects have always been a chock point to hinder flow control technique transition into the practical application,it makes possible to do well the flow control problem related to the wing lift increasing and drag reducing with research and development of flow control technique itself and the improvement of the means such as numerical simulation,test techniques and measurement methods.According to the generation mechanisms of lift and drag,as well as the flow characteristics’ effect on the lift and drag of the airfoil/wing,the feasible strategy of active/passive flow control can be used to increase lift and reduce drag.Lift of the airfoil is an integral result of pressure distributed on the airfoil surfaces,according to the generation mechanisms of lift and the flow characteristics’ effect on the lift of the airfoil,the zero net mass jet flow can be used to improve the pressure distribution on the surfaces of the airfoil to increase lift.Not condidered the interference drag between wing with other components,drag of the wing itself can be divided into four classes,which are pressure drag caused by the windward area,wave drag caused by the shock wave,friction drag caused by viscous air rubbing with the wing surfaces and the vortex drag generated from inclined lift by vortex.According to the generation mechanisms of drag and the flow characteristics’ effect on the wing/airfoil drag,the proper flow control method can be used to reduce drag.Micro vortex generators can be applied to delay or suppress boundary layer separation on the wing to reduce pressure drag and contour bump can be used to weaken the shock wave on the airfoil to reduce wave drag.In the research and application of the flow control technique,because of the complex flow field fixed with spatial and temporal scales,some technical difficulties in the field of fluid dynamics and aerodynamics are not yet resolved,and generally the goals of flow contral are co-related and inter-activated,therefore the numerical simulation and wind tunnel tests can be carried out to clarify the flow control mechanisms,to abstract the flow controller’s parameter impact laws,to evaluate the whole effectiveness of lift increasing and drag reducing.This effort not only offers a support to resolve the difficulties of hindering the flow control technique transmission into the practical application,but also establishes a foundation for choosing the proper active/passive flow control strategy.In this thesis,for the complex flow on the supercritical wing/airfoil and several small-scale flow controllers as the micro vortex generator,the contour bump and the zero net mass jet flow actuator,as well as the complex flow field fixed with spatial and temporal scales induced by them,some flow control problems were investigated such as reducing pressure drag of wing and shock wave drag of airfoli,and increasing lift of airfoil by using numerical simulation methods on the complex flow and wind tunnel refined measurements,innovations are achieved in four aspects,including computation methods and software developments and applications,analysis on the mechanisms of the flow control,abstract on the parameter impact laws of the flow controller,the synthetic evaluation of the control effectiveness,which provided valuable information for the aerodynamic optimization design on increasing lift/reducing drag of the wing.Chapter I gives an review on the active/passive flow control technology development and applications in the lift increasing and drag reducing at home and abroad,by focusing on the micro vortex generator,the contour bump and the zero net mass jet flow actuator,overviews the research contents.Chapter II presents the numerical simulation methods used and developed in the thesis,and then these numerical simulation methods and computing software are verified.For the complex flow field fixed with spatial and temporal scales in the research on flow control,these numerical simulation were based on the RANS equations finite volume method,central difference scheme was used to discrete the viscous fluxes,differential formats contains several windward difference formats and limiters were used to discrete the inviscous flux item,turbulence model include various models.Dual-time step method was used in the unsteady calculation.Inorder to increase the computation efficiency,multigrid accelerating convergence was adopted.Based on the structured grid,the computing mesh used in the thesis had been developed such as multi-block point-to-point,patching,oversetting schemes,therefore the ability to simulate the complex configuration using the structural grid had been improved.Some standard examples,2D/3D complex flow and aircraft practical configurations were used to verify the numerical simulation methods of boundary layer flow,tansonic shack wave flow field,unstead flow,and computing grid generation methods used and developed in the thesis,also used to verify the precision of viscous calculation,time accuracy,computational robustness and calculation efficiency about these numerical simulation software established in the thesis,include 3D boundary layer flow numerical simulation software,2D tansonic shack wave flow field numerical simulation software,and 2D unstead flow numerical simulation software.The verification results indicate that the numerical simulation methods and software are suitble for computing flow control problem.In chapter III,the author investigates the interference between micro vortex generator with boundary layer using the numerical simulation,and pressure drag of supercritical wing with micro vortex generators through the numerical simulation and wind tunnel test.Boundary layer flow,grid generation and accelerating convergence techniques are difficult in numerical simulation of high aspect ratio supercritical wing with micro vortex generators.Based on the 3D steady N-S equations and S-A model,finite volume method was used to discrete,LU-SGS implicit algorithm was used to solve the discrete equation groups,central difference scheme was used to discrete the viscous fluxes and the Roe’s flux difference split was used to discrete the inviscous flux item,the multigrid technique was used to accelerate the convergence.The point-to-point patching mesh technique was used to generate the mesh.The interference between the single micro vortex generator with boundary layer as well as the the flow field and aerodynamic characteristics of supercritical wing-body combination installed with micro vortex generators of various heights and chordwise positions were calculated.Some techniques including force measurement,visualizations with the oil flow,silk and hotwire were used to conduct aerodynamic measurements and visualize the boundary layer characteristics and model flow pattern.The boundary layer features on the wing itself were studied,the boundary layer separation features of wing controlled by the micro vortex generators were investigated,the effects of the micro vortex generators of various heights,chordwise setting positions,spanwise distances and installed angles on the flow field and the aerodynamic characteristics features of the supercritical wing-body combination were investigated.The author analyzed the mechanisms of the micro vortex generators to augment and control the flow near the wall and its contribution in reducing the pressure drag,presented results of the effects of the micro vortex generators with various heights,chordwise setting positions,spanwise distances and installed angles on the drag and lift of the supercritical wing,put forward evaluation suggestions on the effects of the micro vortex generators on reducing drag and increasing lift of the supercritical wing.In chapter IV,the contour bumps were used to reduce wave drag on the supercritical airfoil through the numerical simulation and wind tunnel test.Transonic shock/boundary layer interference and boundary condition treatment on the divergence trailing edge of supercritical airfoil are challenges in numerical simulation of the supercritical airfoil with contour bump.Based on the 2D steady N-S equations and k-? SST model,finite volume method was used to discrete,LU-SGS method was applied in the implicit calculation,central difference scheme was used to discrete the viscous fluxes and the Roe’s flux difference split was used to discrete the inviscous flux item.The effects of the contour bumps with various maximum heights on the flow field and the aerodynamic features of the supercritical airfoil were studied.The surface pressure distribution and wake resistance factor distribution on the supercritical airfoil with contour bump installed were investigated through pressure measurement by the electronic scanning valve and wake flow field measurement by the pressure rake at various income flow angles of attack.The author analyzed the mechanisms of the contour bump to weaken the shock wave strength and its contribution in reducing the wave drag,presented results of the effects of the contour bumps with various heights and income flow angles of attack on the drag and lift of the supercritical airfoil,put forward evaluation suggestions on the effects of the contour bump on reducing drag and increasing lift of the supercritical airfoil.Chapter V investigates the flow field with zero net mass jet actuator through numerical simulation and wind tunnel test,and the lift increase of airfoil by using zero net mass jet through the numerical simulation.Unsteady flow,turbulence caculation and treatment of the boundary conditions are most difficult in the numerical simulation of the airfoil with the zero net mass jet.Based on 2D unsteady N-S equations,finite volume method was used to discrete,the “subspace iteration” of dual-time step method was used to improve the time accuracy in the unsteady calculation,central difference scheme was used to discrete the viscous fluxes,and the Roe’s flux difference split was mainly used to discrete the inviscous flux item and only when differences were compared were used other schemes.Some turbulence models were used to compare the calculation results from different models,including BL model,BLDS model,S-A one-equation model and k-? SST two-equation model.The author investigates the effects of the dynamic mesh,geometrical conservation rate,boundary condition and turbulence model on the calculation results of flow field with the zero net mass jet actuator,the author also investigates the effects of unsteady calculation,difference schemes,turbulence models,the zero net mass jet frequency,velocity magnitudes and the incoming flow conditions on the aerodynamics of the airfoil.The author presented results of the effects of the jet frequency and velocity magnitudes,angle of attack and Mach number of the incoming flow on the lift and drag of the airfoil,analyzed the mechanisms of the zero net mass jet deflecting streamline to change pressure distribution and the role in improving lift of the airfoil,put forward evaluation suggestions on the effects of the zero net mass jet on increasing lift and reducing drag of the airfoil.Chapter VI gives a summary of the thesis,includes the research contents and the technical advancements.Finally,the acknowledgement and lists of references are presented. |
