Unsteady Aerodynamic Forces Mixed Method for Aeroservoelasticity Studies on an F/A-18 Aircraft

摘要

This new mixed (LS and MS) formulation called the MxState method will allow us to obtain the MS approximation without passing through a long iterative algorithm. In this manner we minimize the number of lag terms in the MS approximation term, which means that the lags applied to the two terms:rnΣ_(i=1)~(n_(Lag)) (A_(i+2))/(s+b_i) s and D[sI — R]~(-1) Es will be the same. We compared the flutter speeds and frequencies found by the flutter standard nonlinear method with the flutter speeds and frequencies found by the LS method, and with the flutter speeds and frequencies found by the new mixed state MxState for an F/A-18 aircraft.rnFrom Table 5, we found that the MxState method with a smaller number of lag terms gives results that are very close to the results of the standard pk flutter and the LS approximation method with a higher number of lag terms. Results were presented on an F/A-18 aircraft with 14 symmetric modes and 14 antisymmetric modes.