Actuators are transducers that convert an electrical signal to a desired physical quantity. Active flow control actuators modify a flow by providing an electronically controllable disturbance. The field of active flow control has witnessed explosive growth in the variety of actuators, which is a testament to both the importance and challenges associated with actuator design. This review provides a framework for the discussion of actuator specifications, characteristics, selection, design, and classification for aeronautical applications. Actuator fundamentals are discussed, and various popular actuator types used in low-to-moderate speed flows are then described, including fluidic, moving object/surface, and plasma actuators. We attempt to highlight the strengths and inevitable drawbacks of each and highlight potential future research directions.

Actuators for Active Flow Control

The single dielectric barrier discharge plasma, a plasma sustainable at atmospheric pressure, has shown considerable promise as a flow control device operating at modest (tens of watts) power levels. Measurements are presented of the development of the plasma during the course of the discharge cycle, and the relevance of these measurements to the modeling of the actuator's electrical properties is discussed. Experimental evidence is presented strongly pointing to the electric field enhancement near the leading edge of the actuator as a dominant factor determining the effectiveness of momentum coupling into the surrounding air

Mechanisms and Responses of a Dielectric Barrier Plasma Actuator: Geometric Effects

Multiplee ow diagnostics have been applied to planarpanels covered by strips of glow-discharge surface plasma in atmospheric pressure air generated by the one atmosphere uniform glow discharge plasma. Direct drag measurements, smoke wire and titanium tetrachloride e ow visualization, and boundary-layer velocity proe les were obtained. The plasma generated along streamwise-oriented, symmetric strip electrodes is shown to cause a large increase in drag, whereas the plasma along spanwise-oriented, asymmetric strip electrodes can generate a signie cant thrust. Flow visualization and mean velocity measurements show the primary cause of the phenomena to be a combination of mass transport and vortical structures induced by strong electrohydrodynamic body forces on the e ow, known as paraelectric forcing.

Electrohydrodynamic Flow Control with a Glow-Discharge Surface Plasma

Computational fluid dynamics (CFD) is a powerful numerical tool that is becoming widely used to simulate many processes in the food industry. Recent progression in computing efficacy coupled with reduced costs of CFD software packages has advanced CFD as a viable technique to provide effective and efficient design solutions. This paper discusses the fundamentals involved in developing a CFD solution. It also provides a state-of-the-art review on various CFD applications in the food industry such as ventilation, drying, sterilisation, refrigeration, cold display and storage, and mixing and elucidates the physical models most commonly used in these applications. The challenges faced by modellers using CFD in the food industry are also discussed.

Computational fluid dynamics (CFD) ¿ an effective and efficient design and analysis tool for the food industry: A review

A selected survey of aerodynamic drag reduction at high speed is presented. The dimensionless governing parameters are described for energy deposition in an ideal gas. The types of energy deposition are divided into two categories. First, energy deposition in a uniform supersonic flow is discussed. Second, energy deposition upstream of a simple aerodynamic body is examined. Both steady and unsteady (pulsed) energy deposition are examined for both categories, as well as the conditions for the formation of shock waves and recirculation regions. The capability of energy deposition to reduce drag is demonstrated experimentally. Areas for future research are briefly discussed.

J.S. Shang

Papers

Mechanisms of plasma actuators for hypersonic flow control

Recent research in magneto-aerodynamics

A review of the scramjet experimental data base

Nonequilibrium radiative hypersonic flow simulation

Effect of Surface Plasma Discharges on Boundary Layers at Mach 5