Virtual Mass of Coarse Granular Media

An experimental study to determine the effect of unsteady flow on the hydraulic conductivity of coarse granular porous media is outlined. The acceleration effect was expressed in terms of two variables, i.e., acceleration coefficient, which is function of the well-known inertia coefficient, and the instantaneous flow acceleration. The inertia coefficient was found by comparing the resistance of both steady and unsteady flows through the same porous matrix. The results are given in two forms to show the effect of the unsteady flow on the hydraulic resistance, and to show the variation of the inertia coefficient with Reynolds number. The experimental results show that virtual mass effect does exist in coarse granular porous media, which is the usual construction material for rubble-mound breakwaters. Also, it was found that the acceleration effect becomes more important for large grain porous media, e.g., for particle sizes equal or larger than 40 mm.