Study On The Similarity Criteria And Simulation Method Of The Wind Tunnel Based Virtual Flight Testing

Modern high-performance vehicles are being designed with maneuverability andagility as a high priority which are characterized by high angles of attack and largeangular rate. During the maneuver, the strongly nonlinear aerodynamic forces andmoments not only depend on the vehicle attitude, but also the time history, amplitudeand frequency of the motion, and will induce the rapid change of the motionparameters. Consequently, there are strongly nonlinear coupling between the motionparameters and the aerodynamic parameters of the vehicle. The traditional testtechniques based on the linear superposition principle are hard to effectively simulateand research the actual free flight maneuvers. There is need to develop a new windtunnel test technique that is able to replicate the actual free flight.The Wind Tunnel Based Virtual Flight Testing (WTBVFT) is an innovative testtechnique that is able to replicate the actual free flight and explore the couplingmechanism of the aerodynamics and flight dynamics during the maneuver. The basicWTBVFT concept is to mount the test model on a specialized support system whichallows for the model freely rotational motion, and the aerodynamic loading and motionparameters are measured simultaneously during the model motion. The WTBVFT willbe able to achieve the aim of integrated research on the aerodynamics and flightdynamics, explore the fluid/motion coupling mechanism and apply to the clearance offlight control laws. To develop the WTBVFT, the similarity criteria and simulationmethod are the key theoretical problems that must be firstly resolved.In this thesis, firstly, the similarity criteria and simulation method of theWTBVFT are researched by a combining method of the theoretical analysis, modelingand simulation. Secondly, the primary validation of the similarity criteria is presented.Lastly, the longitudinal flight dynamics with control for a typical missile is numericallysimulated, and the verification tests of the WTBVFT are preformedanalyzed to theprimarily validate the simulation method.This thesis is divided into six chapters as follows:In the first chapter, the background and significance of the present research workis briefly introduced. The current status and progress of the researches in the WTBVFTand the similarity criteria of the wind tunnel test are reviewed. The innovation works inthis thesis are then described in brief.In the second chapter, the statistical analysis of the characteristic parameters andthe dynamic mechanism of the typical maneuvers for the modern aircraft andshort-range dogfight air-to-air missile are analyzed. Then, the simulation requirementsof the WTBVFT for the investigation of these maneuvers are advanced, include the motions and the range of parameters.In the third chapter, the similarity criteria based on the Navier-Stokes equations ofthe air flow and the motion equations of the rigid-body in the environment of theWTBVFT is researched by the theoretical analysis. Then, the relationship of thephysical parameters between theWTBVFT and the actual free flight are analyzed.In the fourth chapter, the simulations of the three-degree-freedom (3-DOF)pitching motion of a typical missile in the vertical plane are performed with theopen-loop and closed-loop control methods. The main differences between theWTBVFT and the actual free flight, and their effect are analyzed. Finally, thesimulation method for the WTBVFT is studied, and the primary validation of thesimilarity criteria is presented. These results indicate that the WTBVFT that usesclosed-loop autopilot control method with the pitch angular rate feedback signal is ableto replicate the actual free flight behavior within acceptable differences.In the fifth chapter, the longitudinal flight dynamics with dynamically deflectedcontrol surfaces for a typical missile is numerically simulated based on the thenumerical methods and grid deformation technique, and the verification test based onthe platform for the WTBVFT in the2.4meter transonic wind tunnel are presented andanalyzed to validate the simulition method. The analysis showed that the WTBVFTwith open-loop control method can only simulate the free oscillation. Using theclosed-loop control method, with the similitude of the control law between theWTBVFT and the actual free flight, the WTBVFT can relatively realistically simulatethe actual free flight.In the sixth chapter, all the works in this thesis are reviewed, and the innovationand the shortages are also described. Moreover, some considerations on the furtherresearch work in this area are listed.Finally, the acknowledgements and references are presented.