INFLUENCE OF BREAKER TYPE ON SURF ZONE DYNAMICS

Abstract

Two of the most significant variables for surf zone hydrodynamic analyses are the mean rate of wave energy dissipation, D, and the longshore current velocity, VI . A detailed theoretical model is extremely difficult to establish (definition of bottom and free surface boundaries, stochastic forcing terms, intense turbulent mixing, etc). The type and amount of existing measured values (laboratory and field) also preclude any accurate calibration, particularly for the more complex formulations. The paper, therefore, presents an average (cross-shore) comparison among state-of-the-art models for D and VI. This illustrates the dependence of these variables on the surf zone dynamic state (closely related to the beach stage, (Short, 1978)), characterized by Iribarren's parameter, ir. Well defined relationships with Ir are obtained for these variables. An expansion of the range of validity of certain models is also attained by calibration of their characteristic free parameters as functions of Ir using a large set of field and laboratory data, and by comparing their general expresion with that of (Losada and S.Arcllla, 1985), which does not include any free parameter. Therefore, theoretical laws for D and VI as simple functions of beach, wave and dynamic state parameters are presented, together with an improved estimation of the empirical coefficients appearing in the various models, suitable for prediction in all ranges of Ir, even though data on the collapsing-surging range are scarce and should require further calibration.