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PO069: Mesoscale-microscale coupling method for Wind Resource Assessment in Large Coastal Area in India
Ru LI, Research engineer, Meteodyn
In the recent year, the large wind farms on complex terrains are growing fast. The simulation of large wind farms on complex terrains becomes a great challenge. Considering the orography and roughness, the micro-scale wind farm simulation characterizes the local wind, via Reynolds-Averaged-Navier-Stokes equation and the turbulence model. The wind climate condition at the large wind farms, the essential thermal stability effect, was rarely considered but now draws more and more attention. The wind resource assessment modeling on the large wind farm focus on three methods: the micro-scale method through solving the thermal effect in micro-scale model; the meso-scale method through refining the resolution to investigate the near ground wind flow in meso-scale model; and the meso-micro coupling method through introducing the meso-scale wind characters into the micro-scale models. The advantages of meso-micro coupling method are that the climate data which cannot be obtained easily in micro-scale model, like the temperature, the heat flux, and the humidity etc., can be resolved in meso-scale model. Then, the time-series or the statistic climate data from the meso-scale model are introduced into the micro-scale model as initial or boundary conditions. The meso-micro coupling method captures better the orography and roughness impacts on wind characters than the meso-scale method because of the fine grid resolution at the surface. A meso-micro coupling method with volumetric forcing is developed in Meteodyn WT. The statistic wind profiles from meso-scale model are used not only as the initial and boundary conditions but also as forces in the computational domain to maintain the statistic meso-scale wind profiles in meso zone. In Meteodyn's mesoscale-microscale coupling method, the Monin-Obukhov length is obtained from the meso-scale data and is used to decide the choice of thermal stability classes in Meteodyn WT. The thermal stability classes range from the unstable to stable conditions. This stability classification is based on Monin-Obukhov Similarity Theory (MOST), in which the turbulent length scale LT, which is used to calculate the turbulence viscosity, depends on the Monin-Obukhov length. A large coastal area of 120km at Rangewadi in the western part of India is studied. The site displays an altitude of 1034m above mean sea level. The dominant winds are the west wind blowing from the sea towards the land and the east wind blowing from the land towards the sea. The thermal effects of breezes on the coast are frequent. Three meteorological stations and a measurement mast were chosen to analyze wind measurements. The results show that the mesoscale-microscale coupling method improves the wind field. The wind speed ratios between the meteorological station and the mast with the meso-micro coupling method performs better than the microscale or the mesoscale modellings.