AIAA-2003-3712 American Institute of Aeronautics and Astronautics 1 Flow Control And Thermal Management Using Dielectric Glow Discharge Concepts Balaji Jayaraman 1 and Wei Shyy 2 Department of Mechanical and Aerospace Engineering University of Florida, Gainesville, FL 32611, USA Abstract The glow discharge creates a thermal plasma far from thermodynamic equilibrium, and can be fruitfully employed for active flow control and thermal management. In the present study, we investigate a capacitively coupled radio frequency discharge plasma generator, where the plasma is generated on the surface of a dielectric circuit board with electrode strips on the top and bottom. A recently developed phenomenological modeling approach is employed to probe force generation as well as aerodynamics and heat transfer characteristics. Qualitative and quantitative evaluations are made based on available experimental measurements to highlight the performance of this device concept and physical implications. Consistent and noticeable increases in lift, drag and heat transfer rates are observed while varying the Reynolds number and angle of attack, indicating that there is substantial potential of applying this concept to manage and control fluid flow and thermal environments. Nomenclature a Plasma breakdown length perpendicular to the surface b Plasma breakdown length along the surface C P Specific heat C L Lift coefficient=L/(ρU 2 /2) d Gap between electrodes D Drag force e Internal energy e c Electron charge E Electric field strength E 0 Peak electric field strength E b Breakdown field strength F Force from glow discharge plasma H Heat transfer k 1, k 2 Electric field gradients K Coefficient of thermal conductivity l Length of the plate L Lift force Nu Nusselt number=Hl/K(T P -T a ) p Pressure Pr Prandtl number= C P μ/K Re Reynolds number=ρul/μ T Time period of voltage cycle T a Ambient fluid temperature T P Temperature of the plate U Inlet fluid velocity V Applied voltage x,y Coordinate axes ρ Fluid Density ρ c Charge number density μ Viscosity τ Shear stress ∆t Discharge duration per unit cycle ε 0 Permittivity of free space=8.852x10 -12 Farad/m 1. Introduction Glow discharge operates in a highly non-equilibrium plasma regime with little thermal effect while exhibiting substantial fluid dynamics characteristics. It offers interesting potential for active fluid flow and thermal control 1-7 . As schematically illustrated in Fig. 1, the plasma generation is achieved using a capacitively coupled mechanism on the surface of a dielectric board containing asymmetrically distributed electrodes on the top and bottom. For example, Corke et al 2-3 demonstrate that the plasma operation enhances lift and also causes an increase in drag ascribed to flow separation downstream of the plasma generating electrode. Physically, the plasma generation produces a wall jet on the surface, essentially acting as a source of external momentum to the fluid. This force is termed paraelectric by Roth et al 4 . In order to develop an analysis framework to probe the physics and engineering implications, a computational model based on simplified electromagnetic field description and the Navier-Stokes equations has been developed by Shyy et al 1 . The paraelectric force is modeled as a body force term in the Navier-Stokes equations governing the fluid flow. The underlying principle behind this treatment is that the paraelectric force can be viewed as that exerted on the local charge concentration of the plasma by the local electric field. This force acts on the fluid inside the elemental volume of interest. This modeling approach is reasonable in light of the plasma being weakly ionized and hence the force on the charge particles is equivalent to the force acting on the fluid itself. Based on such a 1 Graduate Student Assistant 2 Professor and Dept. Chair, Fellow AIAA Copyright © 2003 by Authors, published by American Institute of Aeronautics and Astronautics, Inc. with permission.