The influence of air on the impact of a plunging breaking wave on a vertical wall using a multifluid model

This paper presents the results from numerical computations of plunging breaking wave impacts on a vertical wall using a compressible multifluid Navier–Stokes model that allows for the compressibility of air and aerated water. The air content in water as well as the distance of the breaker from the wall is varied. A detailed description of the wave impact dynamics is given and the oscillation of the entrapped air-pocket is successfully computed. A comparison with experimental results shows however that the damping of these oscillations is underestimated, particularly for a low air-content. This might be due to the fact that the model does not allow for the air-pocket fragmentation. The pressure on the wall is thoroughly investigated. Two regions are distinguished: the first around the location of the maximum pressures where the pressure fluctuations are dominated by the air-pocket oscillations, and the second where the pressure fluctuations are related to steady transverse acoustic waves. Forces and moments induced by the impact are investigated and proved to be in agreement with experimental results. The influence of the oscillations of the entrapped air-pocket is found to be dominant in the dynamics of efforts on the wall, even though the steady acoustic modes play a significant role for a large air-content.

► The oscillation of the air-pocket is successfully computed by a multifluid model.
► The volume of the air pocket is almost independent of the air content.
► The wall experiences oscillating forces and moments.