Review of Turbulence Modeling and Related Applications to Some Problems of Helicopter Flight Dynamics

This paper reviews the statistical treatment of atmospheric turbulence and its influence on the helicopter. Specifically, the review begins with a passing reference to the initial phase from 1967 to 1980, when the groundwork was laid for such a treatment and, in particular, turbulence effects on high‐speed compound helicopters were investigated. With this background, the review then covers the current phase since 1980, when much of the work is directed to conventional helicopters encountering surface‐layer and ship‐airwake turbulence during hovering and low‐speed tasks in the lowest levels of the atmospheric boundary layer. Throughout, the emphasis is on modeling these two types of turbulence and on turbulence‐response sensitivity to the approximations in modeling turbulence and the helicopter. Major topics that are covered include the following: (1) hub‐element, blade‐element, and full‐field turbulence, (2) turbulence simulation in non‐real time, (3) parallel processing, (4) real‐time implementation and pilot evaluation, as well as (5) mixer equivalent turbulence simulation and scaling. The database from model and flight tests is much too limited; this precludes a systematic validation of the current analytical capabilities for modeling turbulence and predicting turbulence response. As done in airplane flight dynamics, complementing this capability with that based on the discrete statistical gust approach offers promise.