Computational Model of a Plasma Actuator

Tuesday, August 01 2006

Scientists are developing computer codes to aid designers in applying these promising devices.

Controlling subsonic aerodynamic flow through the use of plasma actuators is an active area of research in both the Air Force (AF) and the general scientific community. A typical plasma actuator consists of two offset electrodes separated by a dielectric material (see Figure 1). Plasma forms as the voltage difference between the electrodes ionizes the surrounding gas. The electric field can then direct the charged particles in the plasma to transfer momentum to the surrounding, neutral (nonionized) air. Most of this momentum transfer occurs as a result of particle collisions. Experiments have demonstrated the ability of plasma actuators to reattach separated airflow at high angles of attack (see Figure 2), as well as to induce flow movement in an initially stationary air mass.^1,2,3,4,5

The use of plasma actuators for flow control in AF weapon systems may offer several advantages compared to traditional flow control devices such as slats, flaps, and slots. (1) Plasma actuators require no moving parts, which implies both lower costs and potential improvements in reliability and manufacturability.^6,7,8 (2) Their low profile promises improvements related to weapon system size, weight, and aerodynamic drag. (3) As electrical devices, plasma actuators are amenable to high-frequency control and therefore demonstrate effectiveness across a wide range of flow instabilities.² (4) Their ability to respond rapidly to varying conditions increases the weapon system’s aerodynamic agility. (5) For some weapon systems, their use may eliminate control surfaces altogether, which would significantly impact the efficiency of loading, storing, and deploying the units.

Plasma-based flow control devices will also undoubtedly exhibit certain disadvantages with respect to conventional devices. For example, they may not perform well in adverse weather conditions. Furthermore, they require electrical power to operate (although researchers have, in fact, demonstrated the mitigation of these electrical power requirements through a “smart” actuator methodology).⁹