EXPERIMENTAL-STUDY OF WAVE-INDUCED FLOW IN A POROUS STRUCTURE

The kinematics and dynamics of oscillatory flow in porous media are experimentally studied in an idealized porous structure. The concept of seepage velocity, extensively used in literature for the study of porous media, is analyzed. Spatial and temporal fluctuations due to irregularities in the porous structure are evaluated; it is shown that, quantitatively, spatial Fluctuations are always more important. Measurements of the velocity, pressure field and wave height inside the structure reveal that the how behaviour changes, resulting in two characteristic regions: transition and transmission regions. The relative width of the structure, B/L, associated with the formation of a standing wave and resonant conditions inside the structure, was found to be an important parameter to establish the location of the two regions. The transition region is characterized by very irregular records with secondary peaks, little or no dissipation and important higher harmonics in the velocity spectra. Dissipation is the most important factor in the transmission region where the flow tends to become more regular. The porous structure works as a filter, filtering out the higher frequencies as the oscillation propagates towards the leeside of the structure.