Author(s): Claudia Moretto; Dubravka Pokrajac
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Abstract: Turbulent porous media flows often occur in the natural environment (gravel bed streams, aquatic and atmospheric vegetation) as well as in the industrial applications (porous media combustion chambers, heat exchangers, permeable car parks). A large body of literature exists on numerical models of turbulent porous media flows and on experimental results for high porosity media such as forests and aquatic vegetation. In contrast, almost no experimental data are available for turbulence in porous media of moderate porosity, similar to natural gravel. The experiments presented in this paper were carried out on a porous medium made of 12 mm diameter plastic spheres packed in a cubic pattern. The medium was placed in a rectangular channel connecting two constant head tanks. Applied hydraulic gradient was in the range between 0. 015 and 0. 06. The resulting pore Reynolds number (based on the average pore velocity and pore diameter in the narrowest cross section) was ranging between 397 and 860. Axial velocities were measured at a large number of points along a pore using the Ultrasound Velocity Profiler (UVP). The subsequent data analysis is based on the Double Averaging Methodology (DAM), whereby the measured velocities are averaged once in time and once in space (over the length of three spheres). The results presented in the paper include double averaged velocities and spatially averaged higher velocity moments. Further insight is obtained from the time-space correlation analysis. The results are discussed in terms of temporal and spatial scales relevant for turbulence in porous media resembling natural gravel.
Year: 2010