Study Of The Supersonic Low-Drag Low-Boom Aerodynamic Concept

Faster and safer travel has always been the goal of humankind.With the continuous advancement of global economic integration,China’s "Belt and Road" strategy has gradually deepened,and international and domestic exchanges have become increasingly frequent,which has brought huge potential markets for supersonic passenger aircraft in the future.The first-generation supersonic airliner exited the stage of history prematurely due to sonic boom and poor economy.Therefore,reducing the sonic boom and improving the aerodynamic performance are prerequisites for the realization of the next-generation supersonic passenger aircraft.The Busemann biplane configuration can significantly reduce the wave drag by the interference of the shock waves generated between the upper and lower elements in its design condition.At the same time,because the shock waves are confined between the wings,the intensity of the shock wave propagating to the ground is reduced.To some extent,the sonic boom can also be reduced.In this thesis,based on the low-boom and low wave drag property of the Busemann biplane concept,several problems existing in the application of the concept to the future supersonic passenger aircraft has been studied in detail,and A biplane wing/twin-body fuselage innovative configuration has been promoted.The main contents of this thesis are as follows:(1)The numerical discrete methods,viscosity effects,and grid generation methods that affect the near-field prediction accuracy of sonic boom are systematically studied using the internationally mainstream sonic boom prediction strategies.Based on the results of numerical calculations,the following conclusions are summarized,that is,for complex models,in order to improve the prediction accuracy,the viscosity effects should be considered in the simulation;the shock waves should be captured using the entropy-consistent(EC)type schemes;the “cylinder-Mach-cone-aligned” tropology based grid generation method should be used.(2)The principle of the wave reduction and drag reduction of Busemann biplane is theoretically deduced,and the choked-flow and flow hysteresis during its acceleration process are analyzed,and verified with the use of Computational Fluid Dynamics(CFD)method.Aiming at the reduction and elimination of the choked-flow and flow hysteresis effects,a variety of solutions are proposed,including the staggerwing method,the deformed-wing method and the biplane deflection method(applicable to small aspect ratio missile),which have achieved good results.Based on the Radial-Basis Function Neural Network(RBFNN)method and the Genetic Algorithm(GA)method,a design method of the Licher biplane under lift conditions is proposed.The low boom properties of the biplanes are verified by comparing with the diamond wing.(3)The effects of wing parameters on the aerodynamic characteristics of Busemann biplane both at design point and off design point under three dimensional conditions are systematically studied.On this basis,the layout requirements for improving the aerodynamic characteristics of the biplane under design conditions and reducing the choked-flow phenomenon are summarized.That is,reducing the sweep angle of the biplane,the tip-to-root ratio should be within 0 to 0.25,and increasing the winglet are beneficial to improve the aerodynamic performance of the biplane configurations.(4)The choked flow of the biplane under high angle of attack has been systematically studied.The analysis shows that the irreversible choked flow effect will occur when the angle of attack of the farfield inflow increases to a certain value.The wing pitch motion alone cannot eliminate this phenomenon.At this time,the choked flow of the biplane can be reduced by using the method such as the leading-edge flaps wing method,the deformed wing method and the staggerwing method.By using the front and rear flaps as lifting devices,the biplane based aircraft can meet the take-off and landing requirements.(5)Using the Concorde as a reference,a biplane wing/ twin-body fuselage configuration supersonic transport(SST)has been developed by the use of the optimization design method.A relatively complete aerodynamic performance evaluation during the cruise and takeoff phases has been performed.The twin-body fuselage configuration will reduce about 10% of drag compared to the single-body fuselage configuration.At the cruise condition,the proposed biplane wing/ twin-body fuselage configuration will increase about 6% for the lift-to-drag ratio,the level of the sonic boom proposed to the ground will reduce about 1PLd B.Under the same lift conditions,the lift-to-drag ratio is increased by about 2.3% and the level of the sonic boom proposed to ground is reduced by about 1.5 PLdB.