Multi-Objective Optimizations in Rotor Aerodynamics using Variable Fidelity Simulations

This work explains the methodological setup of a variable fidelity framework for the aerodynamic optimization of helicopter rotor blades and demonstrates its capabilities for a single and multi-objective test case. The optimization approach utilizes a Hierarchical Kriging surrogate model. First, a benchmark for single objective optimization containing up to three fidelities demonstrates that the variable fidelity technique significantly reduces the required computational resources, if high fidelity optimizations are necessary. For the hover optimization savings up to 45.0% are achieved and in forward flight optimizations even 83.1%. Extending the framework to multi-objective problems, the usefulness is tested for mid-fidelity optimizations. The resulting Pareto fronts of the single and variable fidelity optimizations are compared to a reference solution. The accuracy of variable fidelity Pareto fronts is generally higher measured by the distance to the reference Pareto front. In the end, three different rotor designs are picked from the Pareto front and the advantages and disadvantages of each rotor are discussed