Aerodynamic Analysis On Near-ground/sea Motion

When winged aircraft, such as missile, airplane and so on, flys at low height, takes off and lands, due to the existence of ground/sea, it will be effected by ground effect. Its lift increases and its drag decreases. Hence its lift drag ratio increases. If the aircraft moves near the sea, wave height and frequency can influence pressure distribution on aircraft surface. Pressure field of aircraft can also change wave shape and motion. Hence the aircraft can be effected again by the wave and its aerodynamic property changes which causes the aircraft to behave differently than it in free space. The stability and safety of aircraft can be influenced.Based on scholar's research achievements at home and abroad, combined with theory analysis and numerical simulation, main work performed in the thesis is as follows:Firstly, force analysis of 2-D airfoil is performed. According to turbulence model-Spalart-Allmaras(S-A) model, standard?-?model and SST?-?model, create corresponding control equation set to resolve. Use wall function method to treat wall. Determine force and moment calculation method of 2-D airfoil and aircraft. Lay the foundation for further calculation.Secondly, adopt standard?-?model and wall function to compute aerodynamic property of airfoil-NACA0015 at different ground clearance and attack angle. Modify the computational model and use hybrid wall boundary treatment method to resolve the problem:computational value is in bad agreement with actual condition at small ground clearance. Decrease computational error greatly. On the basis of the above, use modified method to compute aerodynamic property of symmetric airfoil-NACA0015 and asymmetric airfoil-NACA0413 at different Reynolds number, ground clearance and attack angle. Determine critic relative ground clearance in different cases.Thirdly, on the basis of airfoil near ground motion calculation, combined with grid redistrict method in dynamic mesh technology, analyze unsteady aerodynamic property of airfoil-NACA0015 during its near wavy surface motion. Study on the influence of factors, such as airfoil water clearance, wave length and amplitude to airfoil aerodynamic property. Finally, use dynamic mesh method to compute aerodynamic parameters of some airplane in free stream and flying over a platform in different cases. Compare the computational results in free stream with experimental data in reference to validate the reasonableness of adopted computational model. Analyze the law of influence of height between airplane and platform and airplane attack angle to airplane aerodynamic property. Determine critic height between airplane and platform of some airplane.Much exploratory research and aerodynamic analysis for aerodynamic property of 2-D airfoil and some airplane in near-ground/sea motion is performed in this thesis. Improve the corresponding fundamental theory further. The conclusion can provide some reference for improvement of stability and safety of airplane in near-ground/sea motion, deck taking off and landing, escape and missed approach and design of ground-effect vehicle.