Gust-Response Analysis of Free Elastic Aircraft in the Transonic Flight Regime

manner. Two approaches for CFD-based gust response analysis of free elastic aircraft are presented. The direct approach involves full aeroelastic simulation within the CFD run. The hybrid approach involves computing rigid sharp-edge gust responses in a CFD run, computing the gust input forces due to arbitrary gust proles via convolution, and applying a linear aeroelastic feedback loop to compute the aeroelastic gust resopnses. The latter is highly computationally ecient, as only one relatively short CFD run is required for the computation of the sharp-edge gust responses, after which responses to arbitrary gust proles can be computed in seconds. The former is more elaborate and time consuming, and can be used in cases of critical responses. The use of the two methods was demonstrated on a transport aircraft, ying trimmed at Mach 0.85, 10,000 ft, that passes through one-minus-cosine gust as required by the FAR. Tuned gust analysis was performed rapidly using the hybrid method, and the critical gust response was simulated in a full CFD analysis. The study examined the validity of the use of convolution in the high transonic speeds. For the current test case, the largest errors were in the order of 10%. It is concluded that the use of convolution does not yield accurate responses, but can be successfully used in rapid tuned gust analysis by the hybrid method to pinpoint the critical gust cases, which can then be simulated by the direct CFD-based gust run.