Comparative Study of Aeroelastic Response of Flat Plate Using Frequency & Time Domain Methods

One of the most important quest that drives aviation development is the speed of an aircraft which is limited by the stiffness and damping of a structure associated with an aeroelastic responses such as static divergence and flutter, respectively. In literature, these aeroelastic responses of flat plate are available with an assumption that fluid viscosity and structural damping are negligible. However, these assumptions reflect significant difference between the numerical as well as experimental results. In this research, an effort has been made to include fluid viscosity and wake of flat plate for an aeroelastic response in time domain and make comparison with the results of frequency domain. Firstly, aeroelastic analysis is performed in frequency domain by using commercial code of MSC NASTRAN (Flight Load and Dynamic System Module) in which PK, K and KE methods are used. For this purpose, data available in literature for flat plate is used and the results showed that frequency based approach is very over-conservative and requires fluid viscosity and wake to be incorporated. Also, limited cycle oscillation, hard flutter as well as divergence are observed for different modes from damping and frequency versus velocity plot. Likewise, aeroelastic analysis is performed with the same set of conditions by incorporating fluid viscosity and wake in time domain. This higher order fidelity approach is implemented by using 2-way FSI with dynamic mesh settings using commercial software of ANSYS. FLUENT, Transient Structural and System Coupling are used with time step and simulation time calculated from CFL condition and settling time, respectively. It is concluded that the high fidelity approach is more accurate specially for flexible structures but it is computationally expensive. Hence, it will be a good choice to use time domain for detailed designing whereas frequency based approach is over- conservative and can be used in preliminary design for narrowing the spectrum of search for 2-way FSI.