V. Hohreiter
University of Florida Dept, of Mechanical Engineering P.O. Box 116300 / MEB 237
Gainesville, Florida 32611 -6300 USA
Jacob N. Chung
Department of Mechanical and Aerospace Engineering, University of Florida,
Gainesville, Florida 32611, USA
E. Cummings
Sandia National Laboratories 7011 East Avenue Livermore, CA 94550 USA
T. Postlethwaite
Constellation Technologies 7887 Bryan Dairy Rd., Ste. 100 Largo, FL 33777 USA
Sinopsis
The effect of length scale on turbulence and micro-fluidic mixing was investigated theoretically from first principles and experimentally using a micron-resolution Particle Image Velocimetry (PIV) system. It was determined that turbulence in micro-systems − where the characteristic length scale is less than 10-3 m − the typical three region turbulence model breaks down as large and small eddies become indistinguishable and the presence of turbulent eddies in the near-wall region is entirely possible. Furthermore, micro-scale turbulence may be more accurately modeled as a single fluid region where the range of turbulent eddy size is very narrow and is therefore difficult to induce. Imaging and velocity vector measurement for mixing flows in micro-channels with cross-sections of 200 × 75 µm and 2000 × 75 µm quantified earlier findings in the literature that undisturbed mixing of low pressure, low velocity micro-flows occurs only by molecular diffusion. This experimental work does, however, lay a foundation and develop a control for further investigation of micro-scale turbulence and fluidic mixing establishing that pressure driven micro-flows at low system pressures, despite relatively large values of surface roughness, have no tendency to mix via turbulent motion.