ABSTRACT
Surface/subsurface flow interactions concern a wide range of applications, from beach morphodynamics (swash zone), coastal aquifers (seawater intrusion and tidal effects), to harbour engineering and hydrology (e.g., man-made structures such as porous dykes and earth dams).
The aim of this paper is to study experimentally the oscillatory flows in partially saturated porous media (such as beaches) under tidal/low frequency forcing using a Darcy-scale laboratory experiment (tide machine) that has been designed and constructed at the Fluid Mechanics Institute of Toulouse (IMFT). The system generates low frequency waves on a partially saturated sand column by applying an oscillatory pressure (simple harmonic function) at the bottom boundary of the column. The measurement probes include mainly porous cup tensiometers to measure pressures both positively and negatively with respect to the atmospheric pressure. In this paper, the principles of this tide machine will be presented.
A series of more than 30 experiments on a sand column (1.5 m height) were conducted using this tide machine. For each experiment, we generate a tidal forcing with different amplitudes A0, frequencies ω0 and mean water levels h0.
The results of these experiments will be presented and discussed. The pressure evolution and the phase lag along the ID column will be investigated. The response of the water table height to the applied tidal forcing in terms of amplitude damping and phase lag will be analyzed.
