An experimental study on horizontal two-dimensional transport and diffusivity of dye under irregular waves in surf zone

The experimental study on transport and diffusivity of pollutant in the surf zone can provide a basis for the design of nearshore water environmental protection and pollutant discharge. In the actual situation, the coastal incident waves are irregular waves, this paper studies the horizontal two-dimensional transport and diffusivity of dye under five irregular incident waves based on physical model experiments, image processing and centroid tracking, focuses on the calculation and analysis of the transport velocity in the alongshore and the transport velocity and diffusion coefficient in the cross-shore direction of the dye patch under different wave conditions. The results show that the cross-shore dye transport velocity V_x is about 4.4%～64.7% of the alongshore direction V_y in the case of irregular incident waves; the alongshore dye transport velocity is about 35% of the mean longshore current maximum; the diffusion coefficient in the cross-shore direction is within the range of 2.3×10⁻⁴ ～2.2×10⁻³ m²/s under irregular waves, which is decreases as the increase of irregular incident wave period, and the incident wave height has no significant effect on it.