CFD Modelling of the Wind Climatology at a Potential Offshore Wind Farm Site

摘要

An analysis is made of the wind speed data measured on a mast at the proposed offshore wind farm site off the east coast of England at Scroby Sands to determine diurnal trends in wind shear when the wind is blowing both offshore and onshore. This is compared with a diabatic profile inferred from sea surface temperature, mast temperature and mast wind speed measurements. The diabatic profile does not necessarily give an accurate representation of the wind shear particularly when the wind is blowing from onshore to offshore. Using ground-based and radiosonde ascent data at the nearby coastal meteorological station at Hemsby, the Navier-Stokes computational fluid dynamics (CFD) code CFX-4.4 is applied to model the wind flow onshore to offshore. Comparisons are made between the model predicted wind speeds and measurements made at two heights on the Scroby Sands mast under different atmospheric conditions. The results show the development of a Marine Internal Boundary Layer (MIBL) during a period of ground cooling and advection from onshore to offshore. The height of this layer is compared with an empirical formulation. During a period of ground heating and onshore to offshore flow, a more mixed layer is shown to develop both onshore and offshore with a stable layer aloft and the beginning of a new MIBL. The predicted wind speeds at Hemsby and Scroby Sands show some correlation with the measurements. The predicted wind shear on the mast at Scroby Sands agrees reasonably well with the measurements. The simulations also agree well with the general diurnal trends seen with an onshore to offshore wind.