Influence of Configurational Parameters on the Vortex System of a Rotor in Hover

Abstract

The blade tip vortices in the wake of a rotor are essential for the aerodynamic behavior of a helicopter. Due to the high complexity, a detailed and high resolution simulation of a rotor wake is challenging and in many cases requires experimental validation. In particular, the study of secondary vortices that occur between the helically arranged blade tip vortices is part of the current research. Therefore, this paper presents an experimental study of the influence of different configurational parameters on the development of secondary vortices and their contribution to the vortex breakdown of a rotor in hover. The aim is to gain insight into which configurational parameters have an influence on the occurrence of secondary structures. An extensive database of more than 30 different configurations was created to validate the numerical simulations and methods. It was found that the blade passing frequency is the main contributor to the occurrence of secondary structures. Taking into account all the cases studied, a linear dependence between the number of secondary vortices detected and the blade passing frequency was found