Suppression Of Nonlinear Panel Flutter In The Supersonic Flow And Ground Flutter Test

Panel flutter,which occurs over a critical velocity under the coupling actions of elastic,inertia,and aerodynamic force induced by the transonic,supersonic,or hypersonic airflow,is one kind of self-excited vibration.High-speed aircrafts are subjected to aerodynamic pressure and aerodynamic heating,which should be taken into account when solving the aeroelastic problems.In the last two decades,numerous works have been involved in suppressing panel flutter by active or passive control utilizing smart materials.Experimental investigations on nonlinear flutter behavior of panels have been essentially non-existent.The present study devotes to panel aerothermoelastic problems in the following aspects:The aerothermoelasstic behaviors of laminated composite panels are studied.The classical plate theory and nonlinear von-Karman strain-displacement relation are employed to investigate the aeroelastic behavior of the composite laminated panel.The aerodynamic pressure on the panel is described by the nonlinear piston theory.Nonlinear governing partial differential equations of motion are derived for the panel via the Hamilton principle.The effects of nonlinear terms of aerodynamic pressure on amplitude of limit cycle oscillation are studied.Then effects of temperature,length-to-width ratios and fiber oritention on flutter boundary are analyzed in detail.The flutter and thermal buckling behavior of laminated composite panels embedded with shape memory alloy(SMA)wires are studied in this research.The classical plate theory and nonlinear von-Karman strain-displacement relation are employed to investigate the aeroelastic behavior of the smart laminated panel.The thermodynamic behaviors of SMA wires are simulated based on one-dimensional Brinson SMA model.The aerodynamic pressure on the panel is described by the nonlinear piston theory.Nonlinear governing partial differential equations of motion are derived for the panel via the Hamilton principle.The effects of ply angle of the composite panel,SMA layer location and orientation,SMA wires temperature,volume fraction and prestrain on the buckling,flutter boundary and amplitude of limit cycle oscillation of the panel are analyzed in detail.Investigation on aeroelastic and aerothermal coupling of a composite laminated panel under supersonic flow are carried out.The panel temperature is determined in terms of the flight speed and the environment variables.Ecker's reference temperature method is employed to calculate the heat fleux generated by the aerodynamic pressure.The difference method is employed to solve the transient heat conduction equation.In the numerical simulation,the effects of oblique shock wave on the critical flutter dynamic pressure and amplitude of limit cycle oscillation are considered.Time-domain responses of the panel under interaction of aeroelastic and aerothermal are computed.A new ground flutter test is proposed to determine the critical flutter dynamic pressure of panel.The method to replace the distributed aerodynamic loads to a few concentrated forces is studied.The piston theory is employed to estimate the unsteady aerodynamic pressure induced by the supersonic airflow.The coupling between the panel response and the aerodynamic loads is simulated in real time by measuring the response of the panel,computing the corresponding concentrated forces,and applying these forces to the panel through the shakers.To validate the ground flutter test,numerical results are obtained in the first from a theoretical analysis by applying the Hamiltonian principle with Galerkin method.The experimental results are compared with those numerical ones in terms of the critical flutter dynamic pressure of the panel and the limit cycle oscillation amplitudes.Excellent agreement is observed,which highlights the substantial effectiveness of the ground flutter test in predicting the structural response of the panel under supersonic flow.