Abstract
A weakly compressible smoothed particle hydrodynamics (WCSPH) method is used to simulate the nearshore flow hydrodynamics. The wave induced dispersion and diffusion are determined for monochromatic waves with significant wave height of 0.12 m and the wave period of 1.2 sec (Sop=5%) based on WCSPH wave dynamics. The hydrodynamics of WCSPH model are compared to the laboratory results obtained from series of LDA measurements. The overall mixing coefficients across the nearshore are determined from WCSPH hydrodynamics. The mixing coefficients obtained are compared with the values determined from a series of fluorometric studies performed in a large-scale facility in DHI, Denmark. The results show that the wave profiles are in good agreement with the experimental data. The WCSPH model is proven to be well capable of estimating the dispersion across the nearshore.
Highlights
The nearshore zone experiences pollutant loading through both the shoreline and seaward boundaries
The mixing coefficient was determined for five locations (y={1,2,3,4,5}m) across the nearshore with use of the hydrodynamics obtained from Laser Doppler Anemometry (LDA) and weakly compressible smoothed particle hydrodynamics (WCSPH) model
The mixing coefficients obtained from the temporal variation of shear dispersion from the WCSPH simulations (Tables 4) show that good agreement exists between the numerical model predictions and the mixing coefficients determined for fluorometric tracer measurements of the DHI study
Summary
The nearshore zone experiences pollutant loading through both the shoreline and seaward boundaries. Inman et al (1971) and Bowen & Inman (1974) investigated different aspects of the mixing due to wave and currents in the nearshore area by using dye tracers in the field experiments They defined three different mixing mechanisms due to the surface waves including the processes associated with the wave motion seaward of the breaking point, the mixing due to the breaking wave and the large scale mixing due to the movement of water in longshore and rip currents. The vertical variation of diffusivity parameter is considered for determining the shear dispersion coefficient for both laboratory and numerical study by estimating eddy viscosity for over 20 vertical points at every on-offshore location across the nearshore.
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