Fsi simulation of an aeroelastic system with aerodynamic nonlinearity

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Date
2018-07-01
Authors
Muhamad Khairil Hafizi Mohd Zorkipli
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Abstract
This thesis presents a study of aeroelastic system of an elastically mounted rigid NACA0012 airfoil with aerodynamics nonlinearity. The aeroelastic behavior of a two dimensional wing oscillating is examined by means of numerical simulations. The simulation of NACA0012 is studied numerically through unsteady two-dimensional aeroelastic simulation using ANSYS Fluent 16.1 to evaluate the aeroelastic response of stall flutter at different elastic axis with aerodynamic nonlinearities and found that the aerodynamic nonlinearities are from boundary layer separation, the separation and reattachment of flow around the airfoil. The simulation employed RANS (SST) k-𝜔 model with low Reynolds number correction to capture the physical flow around the airfoil. The dynamics fluid structure interaction (FSI) were achieved by coupling the structural equation of motion with an in-house fluid solver through defined function (UDF) utility in Fluent. Numerical simulations were ran through at three different elastic axis (EA) positions, 0% (leading edge), 18.6% and 35% from the leading edge. The simulations were ran through at free stream velocity range from 4m/s to 14m/s. The results showed two different oscillation amplitudes from the dynamic responses generated by the aeroelastic system of the airfoil, at EA of 0% (leading edge) and 18.6% produced small amplitude oscillation (SAO) while at 35% elastic axis produced large amplitude oscillations (LAO). The validation of numerical simulation showed trends which are similar to experiment results and are found to produce a reasonably comparable limit cycle oscillation (LCO) amplitudes. From the aerodynamic flow aspect, laminar boundary layer separation was found to play an important role for the oscillation sustaining the pitching oscillation in small amplitude oscillation. Leading edge vortex, flow separation and reattachment flow phenomena was found which caused large amplitude oscillation and reversed flow vortices at the trailing edge of the airfoil caused the wing to pitch down and maintaining the oscillation cycle.
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