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Post Doc project: Numerical approach for modelling flow/vegetation interactions using SPH

Starting: 2017

Mediterranean Posidonia (Posidonia oceanica) is an underwater plant crucial for protecting shorelines from erosion. Indeed, algae and underwater plants can play a major role in mitigating the waves and sediment transport in the nearshore zone. From an ecological point of view, these plant meadows are also a biodiversity hotspot that provides habitats to many species. Their impacts have been studied in an attempt to quantify the loss of wave energy, drag and current reduction. However, this dissipation is difficult to estimate given the fact that it is difficult to simulate the movement of plants beneath the waves. Most of the numerical studies represent algae such as rigid bodies with different coefficients of friction, but experimental studies have demonstrated that the effect of vegetation on the flow hydrodynamics were different for rigid or flexible plants. A detailed representation of the plant/water interaction is therefore needed to model properly this complex system.

 

The objective of this project is to try a new approach to simulate the interactions between wave/current and vegetation. The chosen method is to simulate flow and plants through SPH (Smoothed Particle Hydrodynamics). In this model, the plants are defined as a solid that respects Hook's law, which is in direct interaction with the fluid part. Given the properties of the SPH method, the movement of plant under waves or/and current is limited to small scales, but the modelling will permit the determination of coefficient of friction corresponding to a type of plant, that can be further used in a larger scale code.

 

Developments already made possible the simulation of fields of plants but we now need to find modeling solutions (1) to take into account the contacts between plants, (2) to represent plants with several stems (leaves) and (3) to add a third body to represent the sediment transport.

 

The project aims at building a numerical simulation relying on experimental studies made in laboratories (the experimental data from Sylvie Barsu, LMFA, Lyon, the experimental data from Caroline Le Bouteiller and Jeremy Venditti at Simon Fraser University, Canada, and in-situ data from Eléonore Paquier et CEREGE, Aix-Marseille) and on theoretical approaches.

 

 

 

Within TEC21, this innovative project will reinforce the existing collaborations between LEGI and IRSTEA.

 

 

On left: SPH simulation of a flexible plant in a wave (Larroudé & Oudart), on right: experimental investigation (Luhar & Nepf)
On left: SPH simulation of a flexible plant in a wave (Larroudé & Oudart), on right: experimental investigation (Luhar & Nepf)

PI: Philippe Larroudé; Post-doc: Thibault Oudart


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