Adjoint Based Aerodynamic Optimisation of a UCAV

*† ‡ An optimisation study for the 1303 UCAV has been conducted attempting to minimise drag in the cruise configuration subject to constraints designed to avoid flow separation at takeoff. The methodology has been developed for pr oducing credible designs for this class of wing early in the design process and hence minimising assumptions made during aircraft preliminary design. The design is achieved iteratively using a gradient based SQP optimiser where the objective is calculated using an in house multiblock CFD code MERLIN in Euler mode. The objective gradients are efficiently calculated using an in house discrete adjoint code adjMERLIN. The high lift constraint is based on a quasivortexlattice method with empirical relationships which place limits on the ‘attainable’ leading edge thrust aiming to avoid flow separation. The resulting designs are analysed using MERLIN in RANS mode with the kω turbulence model which shows that desi gns can be obtained with similar cruise drag to the original planar wing but with considerably improved high lift performance.