Optimization of Rotor Blade Airfoils Using Compressible Unsteady Flow Simulations for Hover and Forward Flight Performance

Abstract:
A multi-objective optimization of a rotor blade airfoil is presented using compressible unsteady Reynolds-averaged Navier-Stokes simulations directly within the optimization loop. The baseline SC1095 airfoil is optimized using NSGA-II with two objectives: pre-stall aerodynamic efficiency representing hover performance, and lift hysteresis loop area representing dynamic stall severity. The optimized airfoil exhibits increased maximum thickness with an aft-shifted crest and substantially higher camber. Static polars show improved lift-to-drag ratio at $Ma = 0.5$ and $0.6$. Hover performance is essentially unchanged relative to the baseline. In forward flight, a progressive power penalty is incurred above $\mu = 0.2$, attributed to higher profile drag at advancing blade Mach numbers. Dynamic stall simulations show an 80% reduction in peak drag and a 50% reduction in peak pitching moment excursion relative to the SC1095, demonstrating the effectiveness of the optimization for retreating blade conditions.

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