Transition Process to Turbulent Flow in Porous Media

Turbulence in porous media has attracted much interest recently, and many turbulence models have been proposed [1-12]. However, the mathematical treatments in some turbulence models have been developed without reference to the unique structure of vortices in porous media. The further development of the turbulence model and the theoretical argument in the transition flow regime need the experimental verification of the microscopic flow field in porous media, but the geometric complexity of porous media brings about technical difficulties of the measurement and the visualization. Therefore, we adopt the flow through a bank of cylinders in a narrow gap as a model for the flow through porous media, and perform the PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) techniques to examine the microscopic flow field in porous media. We have confirmed that the solid matrix in porous media plays an important role in the vortex diffusion. The large vorticity at the throat produces such vortex as the swirl flow. On the other hand, the obstruction due to the solid matrix forces such large vortex as a Ka´rma´n vortex to be dissipative. Furthermore, the present experimental results are in agreement with our model [2] for the production and dissipation of turbulence.