A<scp>ERODYNAMICS OF</scp>S<scp>MALL</scp>V<scp>EHICLES</scp>

TLDR

Boundary‑layer behavior on airfoils, including quasi‑steady attached flow and unsteady vortex wake effects, is critical for designing small aerial vehicles. This review examines the aerodynamic challenges and the influence of Reynolds number and aspect ratio on the design and performance of small fixed‑wing aerial vehicles. The authors review examples of small UAVs, survey analytical models for oscillating and flapping‑wing propulsion, and discuss how Reynolds number and aspect ratio affect fixed‑wing design. Experimental studies of boundary‑layer behavior, including laminar separation bubbles, and complementary tests that guided the design of a successful ornithopter are presented.

Abstract

▪ Abstract In this review we describe the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies, including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful ornithopter are also described.