This paper presents a discussion on the role of impulsive pressures induced by plunging breakers acting on gravel beaches. In previous works, this process has been hypothesized to play a major role in the observed sediment transport on these beaches. Thus, a diagnostic investigation is carried out here in order to elucidate, in more detail, the anatomy of the impulsive signature in the pressure signal. For this purpose, we employ an integrated approach, which comprises full scale laboratory measurements and their comparison against model results from a well-validated phase/depth resolving numerical model based on the Reynolds-Averaged Navier-Stokes (RANS) equations. Agreement between observations and model predictions allows us to investigate the contribution of each of the acceleration terms in the momentum balance under the wave-impact event by means of the numerical model. The discussion is presented in order to understand how impulsive pressures are generated under plunging waves and their role in sediment mobilisation. Consistent with prior studies, numerical results show that under plunging breakers the local acceleration (du/dt) alone cannot be used as a proxy for pressure gradients. In addition, the importance of the term wdu/dz of total acceleration is recognised for first time. Results from this study suggest that for different types of breaking a different characterisation of the pressure gradient may be sought.
Pedrozo-Acuña, A., Torres-Freyermuth, A., Zou, Q., Hsu, T-J., & Reeve, D. E. (2009). On the role of impulsive pressures induced by plunging breakers acting on gravel beaches. In Proceedings of Coastal Dynamics 2009  World Scientific Publishing. https://doi.org/10.1142/9789814282475_0079