Investigation of aeroelastic behavior of a missile canard with fluid-structure interaction

Canard is a type of control surface used in airplanes and missiles. Aeroelastic behavior of a canard system should be known to comply with the control system which is used to actuate the canard. However, mechanical gaps causing free-play make the system behavior nonlinear and determining the dynamic characteristics of the canard becomes a challenging problem. Based on the mentioned problem, aeroelastic behavior of a canard system which has free-play in its shaft-actuator connection is investigated. The aeroelasticity analyses are performed with two way loosely coupled Fluid Structure Interaction (FSI) method. As parts of FSI, Computational Fluid Dynamics (CFD) analyses are done with STAR-CCM+ and ABAQUS is used to accomplish Finite Element (FE) calculations. FSI procedure followed in the thesis is verified with the flutter test results of AGARD 445.6 wing. Before the FSI analyses which are performed to obtain flutter onset, FE and CFD models are validated separatelly. Then, FSI anaylses are repeated with different inlet pressure until undamped wing oscillations occured while the inlet Mach number and temperature are kept constant. The flow conditions which bring about undamped oscillations give the flutter onset. According to flutter speed indexes and flutter frequency ratios calculated with flutter onset conditions, the values obtained by FSI method are close to the test results and maximum error is lower than 10%. After flutter analyses of AGARD 445.6 wing, aeroelastic analyses of a canard which has free-play in its shaft-actuator connection are investigated. Free-play is modelled with a connector element and zero torsional stiffness is introduced between free-play boundaries. Before the FSI analyses, FE model is verified with modal test-analysis comparison on a similar canard model. During the FSI analyses, overset mesh method is used to prevent excessive deformation of elements which are in narrow gap between canard and missile body in the CFD model. Three different angle of attack positions and free-play sizes are evaluated in FSI analyses. As a conclusion of the study, it is acquired that canard and shaft vibration amplitudes increase with increasing angle of attack and free-play while the response frequencies decrease. In case of zero free-play condition, response frequencies are close to first mode of the canard; however, free-play effect reduces response frequencies.