Abstract
The vertical tail buffet induced by the vortex breakdown flow is numerically investigated. The unsteady flow is calculated by solving the RANS equations. The structural dynamic equations are decoupled in the modal coordinates. The radial basis functions (RBFs) are employed to generate the deformation mesh. The buffet response of the flexible tail is predicted by coupling the three sets of equations. The results show that the presence of asymmetry flow on the inner and outer surface of the tail forced the structural deflection offsetting the outboard. The frequency of the 2nd bending mode of the tail structure meets the peak frequency of the pressure fluctuation upon the tail surface, and the resonance phenomenon was observed. Therefore, the 2nd bending responses govern the flow field surrounding the vertical tail. Finally, the displacement of the vertical tail is small, while the acceleration with a large quantitation forces the vertical tail undergoing severe addition inertial loads.
Highlights
LARGE swept delta wing combined with vertical tail configuration is widely used by modern flight vehicles. is kind of aerodynamic configuration is designed to reduce drag and improve the manipulated performance at a large attacking angle
Wentz [1] conducted a wind tunnel experiment to investigate F/A-18 tail buffet problem, and the results revealed that the buffet is a phenomenon of resonance induced by the excitation of vortex breakdown flow, while the frequency bandwidth of the excitation covers the natural frequency of tails. e characteristics of buffeting are different from the traditional flutter or limit cycle oscillation (LCO). e buffet displacement with slight amplitude produces large acceleration responses that make the tail suffer from severe inertia force loads and fatigue failure
Kandil [4,5,6,7,8] investigated the bending-torsion interaction effect on the tail’s buffet, as well as the effect of freestream Mach number on the tail’s buffet. e results revealed that the deflections and loads of the coupled bending-torsion response case are substantially lower than those of the uncoupled bending-torsion response case, and the buffet loads in the transonic flow are lower than those in the subsonic flow
Summary
LARGE swept delta wing combined with vertical tail configuration is widely used by modern flight vehicles. is kind of aerodynamic configuration is designed to reduce drag and improve the manipulated performance at a large attacking angle. The vortices emanating from the leading edge of the delta wing might breakdown before reaching the vertical tail at a certain attacking angle. In such cases, the vertical tails suffer from the wideband frequency excitation of the highly turbulent flow, which would produce a severe buffet on the tails. Findlay [2] simulated leading-edge vortex breakdown flow nearby vertical tails by solving thin-layer Navier–Stokes equations. Attar [11] conducted numerical simulations for the full-span delta wing buffet in the vortex breakdown flow. Current time t: t->t+∆t: Solve RANS equatiuons Obtain Aerodynamic Force f f at CFD mesh CFD-CSD Interface data transformation modal Force QF advance structural dynamic equations in time
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