Characteristics of Ground Effects of an Unmanned Aerial Vehicle with High-aspect-ratio Flying Wings during Take-Off

Zhigui Ren,Qinghe Zhao,Junli Wang,Bolin Feng,Wensheng Zhang

doi:10.5755/j01.mech.24.5.20934

Abstract

In view of the take-off process of an unmanned aerial vehicle (UAV) with high-aspect-ratio flying wing configurations, the influences of ground effects on longitudinal aerodynamic characteristics of the UAV were investigated. By using a numerical simulation method, the effects of different angles of attack, heights from the ground, and take-off velocity on the UAV were studied. Moreover, based on comparisons with test data in previous literature, the numerical calculation method was verified to be accurate. The height from the ground is the primary factor influencing longitudinal aerodynamic characteristics of the UAV. With the increase in height from the ground, the lift and drag coefficients of the UAV, and its pitching stability, increased. When the angle of attack was small, a large suction area was generated on the lower surface of wings with a large suction amplitude therewith. This results in a large range of downwash. As the angle of attack increased, the lower surface of the trailing edge for wings presents weakening downwash. As the take-off velocity rose, the suction area on the lower surface of the UAV, and its amplitude, gradually decreased, and the negative pressure on the upper surface also decreased to a certain extent. The research results can provide a certain theoretical basis for the safe design of take-off operations for high-aspect-ratio UAVs.DOI: http://dx.doi.org/10.5755/j01.mech.24.5.20934

Highlights

With the continuous development of large and heavy-duty unmanned aerial vehicles (UAVs), take-off and landing technology has become a key link restricting its development
For UAVs with flying wing configurations that are difficult to be controlled in the longitudinal direction, ground effects exert significant influences on manipulation design for safe take-off, in view of UAVs with medium-aspect-ratio flying wing configurations, it is necessary to study the characteristics of ground effect during take-off and find accurate relationships between longitudinal aerodynamic characteristics with height from the ground, take-off velocity, and angle of attack
The cross-section of the UAV wing is a thick airfoil with a curved edge at the trailing edge

Summary

Introduction

With the continuous development of large and heavy-duty unmanned aerial vehicles (UAVs), take-off and landing technology has become a key link restricting its development. The large scale of UAVs with medium-aspect-ratio flying wing configurations strengthens the interaction of UAVs with the ground when taking off: this influences the longitudinal aerodynamic characteristics of UAVs. When the take-off height of UAVs with flying wing configurations is different, the ground effects vary correspondingly, so elevator deflection and take-off velocity of UAVs have to be adjusted according to the changes in ground effect. For UAVs with flying wing configurations that are difficult to be controlled in the longitudinal direction, ground effects exert significant influences on manipulation design for safe take-off, in view of UAVs with medium-aspect-ratio flying wing configurations, it is necessary to study the characteristics of ground effect during take-off and find accurate relationships between longitudinal aerodynamic characteristics with height from the ground, take-off velocity, and angle of attack

Objectives

Methods

Results

Conclusion