Gas compressor

Turbulence

Engineering

Propulsion

Aerospace engineering

Micro air vehicle

Reynolds number

Fluidics

Aerodynamics

Actuator

Vortex

Telecommunications

Data mining

Computer science

Airplane

Physics

Propulsive efficiency

Flow control (data)

Lift (data mining)

Automotive engineering

Electronics

Flight control surfaces

Mechanics

Electrical engineering

Annual Review of Fluid Mechanics

The pervasiveness of unmanned air vehicles (UAVs), from insect to airplane scales, combined with active flow control maturity, has set the scene for vehicles that differ markedly from present-day configurations. Nano and micro air vehicles, with characteristic Reynolds numbers typically less than 10 5 , rely on periodically generated leading-edge vortices for lift generation, propulsion, and maneuvering. This is most commonly achieved by mechanical flapping or pulsed plasma actuation. On larger UAVs, with Reynolds numbers greater than 10 5 , externally driven and autonomous fluidic systems continue to dominate. These include traditional circulation control techniques, autonomous synthetic jets, and discrete sweeping jets. Plasma actuators have also shown increased technological maturity. Energy efficiency is a major challenge, whether it be batteries and power electronics on nano and micro air vehicles or acceptably low compressor bleed on larger UAVs. Further challenges involve the development of aerodynamic models based on experiments or numerical simulations, as well as flight dynamics models.

Flow Control for Unmanned Air Vehicles