MODERN HELICOPTER AERODYNAMICS

TLDR

Modern helicopter aerodynamics is highly complex, making flow measurement, modeling, and prediction difficult and expensive, and researchers have employed sophisticated experimental and computational techniques to study the three‑dimensional, unsteady rotor wake and its impact on blade pressure distribution. The article aims to discuss the basic principles of modern helicopter aerodynamics. The authors review modern computational and experimental methods, ranging from vortex techniques and full 3‑D Navier‑Stokes simulations to classical probes and laser velocimetry. Typical wake structure and blade pressure distribution results in hover and forward flight are presented, showing that significant progress has been made in the past decade and future advances are expected.

Abstract

▪ Abstract Modern helicopter aerodynamics is challenging because the flow field generated by a helicopter is extremely complicated and difficult to measure, model, and predict; moreover, experiments are expensive and difficult to conduct. In this article we discuss the basic principles of modern helicopter aerodynamics. Many sophisticated experimental and computational techniques have been employed in an effort to predict performance parameters. Of particular interest is the structure of the rotor wake, which is highly three-dimensional and unsteady, and the rotor-blade pressure distribution, which is significantly affected by the strength and position of the wake. We describe the various modern methods of computation and experiment which span the range from vortex techniques to full three-dimensional Navier-Stokes computations, and from classical probe methods to laser velocimetry techniques. Typical results for the structure of the wake and the blade pressure distribution in both hover and forward flight are presented Despite the complexity of the helicopter flow, significant progress has been made within the last ten years and the future will likely bring marked advances.