Wind effects on trees: computational poroelastic modelling and application to shelterbelts along infrastructures.

Planted shelterbelts are commonly used to reduce wind speed and protect structures and infrastructures. The shape, the characteristics and the distribution of the trees forming the barrier are key parameters to determine the efficiency of the shelterbelt in terms of wind reduction. The mathematical modeling of the above phenomena is a challenging task, because of the interaction between the multiple components of wind and vegetation, the description of the trees as porous media in which the wind can flow through, the mechanical interaction between the wind and the trees, the finite resistance of the trees to loads and stresses. Moreover, the problem results being highly multi-scale: from km-long line-like infrastructures to mm-sized petioles and leaves through the turbulent wind energy cascade. The accurate and efficient computational simulation of the above phenomena is of paramount scientific and industrial importance, because of the lack of similarity in scale wind tunnel tests and of the costs and uncertainties in full scale field tests. The present MSc thesis aims at tackling the above issues. A coupled multiphase mathematical model is adopted in the framework of homogenized continuum mechanics by adopting the Pressure Jump (PJ) method, coupled with a mechanical response. The resulting computational model is implemented in the open source OpenFOAM code, for what concerns the fluid dynamic of the problem, and in Python for what concerns the mechanical response of the trees. The MSc Thesis takes advantage of the computational approach to evaluate different porosity descriptions, in both trends and dependencies, and to assess the efficiency of the shelterbelts with respect to model parameters and barrier design. The developed approach is applied to benchmarks characterized by high-Reynolds wind flow around line-like vegetated barriers immersed in the atmospheric boundary layer, in order to protect line-like infrastructure such as Railway Systems (RS). The Thesis has been developed in the framework of a joint research between the Departments of Mathematics and Architecture and Design at Politecnico di Torino and Optiflow Company (Marseille, France). In particular, Optiflow Company has hosted the MSc candidate during a 5 months stage at its facilities in Marseille.