Contact PI : Julien Touboul - MIO
Project duration : 31 January 2021 - 31 January 2024
This research project follows on from the ANR ASTRID MORHOC'HThis study focused on the processes that have a significant impact on wave propagation in the presence of a current whose structure varies vertically. Such currents are not uncommon in coastal areas, where the combined effects of wind and bathymetry can profoundly modify the vertical profile. The physical and numerical modelling of such zones is a strategic issue, both in the civil domain (coastal safety, renewable marine energy, etc.) and in the military domain (landing, rescue, naval applications).
Two results from the project are of particular interest here. The MORHOC'H project enabled us to develop a particularly robust experimental device aimed at experimentally controlling the vertical structure of a current in a hydrodynamic channel. In addition, a new model, called CMS, has been developed to extend the field of application of phase-resolved swell propagation models to take into account configurations involving high current vorticity.
The MORHOC'H 2 project therefore aims to increase the degree of maturation of these two results, in order to bring them closer to use in real conditions. Firstly, the current profile control device will be extended to larger configurations, and will become applicable in three-dimensional basins. Many industrial players operating hydrodynamic test basins will then have access to it. In addition, the CMS propagation model will be coupled with the Community coastal hydrodynamic circulation CROCOdeveloped by the SHOM, l'IRDthe CNRS, l'IFREMERand theINRIAto make it usable in realistic conditions. In this way, the improvements resulting from the initial project will become accessible in realistic environments. The two approaches to coastal modelling, physical and numerical, will thus become more effective, and will be able to describe more realistic situations.
Presentations from the Project Launch Meeting
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| Presentation of the MIO | Presentation of OCEANIDE | Presentation of the M2C | Presentation of SHOM |
Overall objectives, scientific/technical challenges
The overall objectives of the programme are to extend the applicability of the results of the MORHOC'H project to more realistic configurations in coastal modelling, involving flows with high vorticity. The experimental, mathematical and theoretical hurdles were overcome in an initial phase during the ANR ASTRID MORHOC'H project. This new programme therefore aims to overcome the technical difficulties resulting from this approach.
Experimentally, the current structure control device was developed in a small, two-dimensional channel. Different screens of the desired shapes were manufactured. The aim here is to generalise the technique to larger basins, enabling more operational shape control.
In numerical terms, the CMS model obtained previously had only been developed in Matlab, on a structured Cartesian mesh, and was therefore unusable in real coastal conditions. The aim here is to couple this tool with coastal hydrodynamic circulation software, while taking advantage of the best numerical approaches (meshing, parallel calculation, temporal integration, etc.) developed for CROCO. The model can thus be used in realistic coastal modelling conditions.
Work programme
Given the scientific approach envisaged here, the project will be divided into four major technical tasks, in addition to the two tasks of managing and disseminating the results.
The first will be to implement the numerical version of the CMS model, coupled with the CROCO coastal hydrodynamic circulation model. This task will be carried out in very close collaboration with SHOM and IRD, in order to guarantee the interoperability and numerical efficiency of the propagation models obtained. This development effort will last for most of the project, but will be segmented so that validation can be carried out throughout the project.
The second of these technical tasks is to design the experimental device, deploy it and test it in the FIRST ocean engineering basin at La Seyne sur Mer. This task will be carried out during the first year of the project, so that the results can be used for validation purposes, by comparing digital data with experimental data in a controlled environment.
Finally, a validation task on a realistic site will be carried out in task 4. For this purpose, the Raz Blanchard site, a demonstrator for an offshore tidal turbine project, is well known for testing propagation and circulation models in the conditions of strong, highly sheared currents that it harbours. This site, which has been extensively documented experimentally, will provide an excellent demonstration of the progress being made in the natural environment.
Scientific, technical and economic spin-offs
Models of swell and its propagation in coastal areas are becoming more and more effective, thanks to advances in mathematical modelling, the growing power of computing resources and the ever-increasing amount and quality of measurement data.
However, propagation models have their limitations in the case of steep bathymetries, or in the presence of non-homogeneous currents, in particular because of the limits of validity of the methods used to calculate the propagation equations, which are generally based on gentle slopes and non-sheared currents.
The same applies to physical models of coastal propagation and circulation. These models, which are becoming more and more effective in terms of current speed, attainable depth and swell range (in terms of frequency, amplitude and directionality), are making constant progress. However, to date, no industrial basin has the tools needed to control the vertical structure of the current in fine detail, while studying its interaction with the swell.
These difficulties have been overcome on a laboratory scale, as part of the MORHOC'H project. This research programme will bring these advances to a sufficient level of maturity to make them usable under realistic conditions. In this way, the current control device will become usable under conditions more in line with industrial reality. In addition, the CMS swell propagation model will be coupled with the CROCO coastal hydrodynamic circulation model. These two tools will thus become accessible to the many players involved in coastal modelling, whether civil or military, public or private.
