An evaluation of the use of a dynamic wake theory for edgewise rotors at high advance ratios

Abstract

Dynamic wake theories are widely used in rotorcraft simulation codes and continue to be a valuable resource even though computationally heavy methods, such as vortex lattice methods and CFD, have become more accessible. As next-generation rotorcraft continue to push the boundaries of performance and maximum speed, it has become increasingly important to gauge the accuracy of rotorcraft simulation codes. For many helicopters, it is imperative that the rotor is slowed in the high-speed regime, causing a large portion of the rotor disk to be submerged in reverse flow. It is in these conditions that dynamic wake theories have not undergone a rigorous analysis. Fortunately, wind tunnel experiments have been performed at high advance ratios so that the validity of new simulation codes can be assessed. To test the predictions of a rotor aerodynamic model which utilizes a dynamic wake theory is the pursuit that motivates the following investigation. Detailed aerodynamic analysis of a slowed UH-60A rotor operating at μ = 0.80, 0.90, and 1.00 is provided. In addition, the results from this investigation are compared to experimental data and other computational validation studies which use hybrid CFD and free wake methods. Conclusions regarding slowed-rotor behavior at high advance ratios can be drawn based on this analysis.