Predicting below-surface pore velocity profiles in porous media from above-surface wind speed and porous medium gas permeability

Below-surface horizontal pore air velocity profiles in porous media in response to above-surface wind conditions were measured for 16 combinations of wind speed (1.4 – 5.7 ms^-1) and main wind gust frequency (0 – 1 Hz) in four granular porous media (particle size: 0.6 – 10 mm) yielding 64 combinations of wind condition and porous medium. Measurements were carried out under controlled (wind tunnel) conditions using a recently developed experimental gas tracer tracking method. Gusty wind conditions were induced by a wind driven propeller capable of variable rotation frequencies.

A recent empirical model for predicting wind-induced horizontal pore velocity in porous media (using one empirical parameter, B together with surface wind speed as input) was validated against the experimental data and found to provide accurate approximations. Further investigations revealed that B could be accurately predicted from porous medium gas permeability. Overall the results indicate, that it is possible to accurately predict below-surface wind-induced pore velocity profiles based on the above-surface wind speed profile and the porous medium gas permeability.