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The European High Performance Computing Joint Undertaking (EuroHPC JU)

Direct numerical simulation of progressive sea WAVEs in shallow waters: mass TRANSPort over rippled bottom (WAVETRANSP)

Awarded Resources (in node hours)
System Partition
4 March 2024 - 3 March 2025
Allocation Period


The free-surface flow induced by progressive non-breaking wind waves propagating in shallow waters over a  horizontal bottom will be investigated by means of Direct Numerical Simulations (DNS). The DNS differ in the bottom surface configuration which is either smooth or rippled. The values of the parameters are relevant for the study of wind waves in the coastal environment. The DNS results will allow to characterise and quantify the transport of sediments in the near-bottom region as well as the distribution of floating plastic and biological particles (e.g. harmful micro-algae) close to the free-surface.

The preliminary results obtained so far in the context of smaller allocations (project "WAVEMATE" on Galileo 100, CINECA) were shown at the APS meeting (Division of Fluid Dynamics), Indianapolis, Nov 2022, and at the 18th ETC, Valencia, Sep 2023.


The DNS results will allow us to investigate the effects of the turbulent vortices generated at the sea bottom by wind waves on the net mass transport of marine debris and on the distribution of floating particles.

The shoreward velocity of smaller and lighter particles is expected to be larger than that of particles moving close to the bottom  while the wave orbital motion redistributes the particles so that their concentration is larger under the wave crest than under the wave trough. A little is known about the combination of the phenomena associated with the propagation of wind-waves such as Stokes drift, offshore drift, bottom turbulence and Longuett-Higgins current, in particular in the presence of sand ripples (small scale bedforms).


To the best of proponents' knowledge, this is the first time that the turbulence generated at the seabottom by free-surface waves is investigated by means of DNS. The mutual effects of waves on turbulence can be understood because turbulence is not imposed externally as in previous works, but generated and driven by progressive waves for values of the parameters which characterise actual sea waves and allow turbulence to appear spontaneously. Indeed, the dynamics of the boundary layer and of the free-surface are coupled.

The project is the first step towards the use of DNSs at spatial scales relevant for coastal engineering applications. Considering the wave breaking and the bottom morphodynamics are the next steps of the present research line which still require significant developments of the code.


The proponents have long investigated the sediment transport associated with the oscillatory boundary layer which , at the leading order of approximation, is the flow induced by monochromatic wind waves at the sea bottom.

However, the wave-induced orbital motions, near-shore currents and vortices shed by bedforms can significantly affect the turbulence properties and the transport of sediments on the seabed, while particles less dense than water tend to migrate towards the free-surface.

The planned simulations will allow us to investigate the flow properties and mass transport under sea waves as well as the mechanism of formation of preferential floating-particle patterns at the free-surface.


The detailed knowledge of the fluid dynamics under non-breaking wind-waves will lead us to unexplored scenarios and to improve significantly the capability to predict the fate of MPs and micro-algae in the coastal environment. The results of the project will be useful to improve (i) sediment transport models, (ii) marine-debris dispersion models and (iii) bedform evolution models.