Toward a high-fidelity helicopter rotor redesign framework

Limitations of rotorcraft generally fall into the categories of speed, noise, vibration, and range, Rotor blade design plays a large role in how these limitations may be mitigated. Designers are always looking for new ways to design more optimum rotor systems. Often the tools used are low fidelity tools with simplified aerodynamics. A problem with this is that these tools often lack a first principles based approach that is needed for new and novel designs, However, high fidelity, first principles based analysis tools have disadvantages related to complexity and run time. Though not as accurate, low fidelity tools are still physics based, have been proven useful in optimization, and have low analysis run time. The research presented uses first principles analysis and simplified physics based analysis together in a process to redesign a rotor blade's tip shape and twist. The design framework ModelCenter® is used to integrate the comprehensive rotorcraft analysis code RCAS with the aeroacoustics code PSU-WOPWOP into a low fidelity framework. A design of computer experiments is performed, 2^nd order Response Surface Equations of objectives are built and subsequently used to examine four million stochastically generated design variable combinations in what is called Monte Carlo simulation. High fidelity tools are used to evaluate an optimum from this group. The optimum is found to exhibit better performance characteristics and reduced noise. An a posteriori examination of vibratory characteristics reveals the optimum produces more vibration in forward flight than the baseline, highlighting the need to consider vibration in during the first phase using low fidelity tools. In a effort to better select designs for future high fidelity analysis, additional low fidelity experiments are performed to improve the surrogate models. New surrogate models using 4th order Response Surface Equations are used to find optimums in each objective, These new optimum designs are checked in the low fidelity model and found to provide improved designs, but questions on global optimality still remain. Future work will focus on further automation of the high fidelity model and its use in the examination of these and other design configurations; moving closer toward a high-fidelity helicopter rotor redesign framework.