Towards Low-Noise Design of a Proprotor with the Vortex Lattice Method and Gradient-Based Optimization

This work aims to combine an aerodynamic model based on the unsteady vortex lattice method with an acoustic model provided by Farassat's formulation 1A to perform gradient-based optimizations of a proprotor with aerodynamic and acoustic constraints. The resulting combination of tools is applied to the problem of designing a single proprotor operating at a cruise condition, with and without an acoustic constraint and wing placed downstream of the proprotor rotation plane. Results are compared to a baseline design studied previously, and to similar optimizations performed with a simpler blade element momentum theory aerodynamic model. Each optimization case achieved feasibility and made significant improvements in the objective function, but the optimality criterion was not satisfied. Overall the designs the optimizer found roughly comported with our previous experience with similar problems, with some discrepancies that are discussed.