Parametrization of homogeneous forested areas and effect on simulated dose rates near a nuclear research reactor.

One of the major uncertainties in dispersion-based simulations at the local scale is the representation of terrain effects. The aim of the current study is to quantify this type of uncertainty for dose-rate predictions over a homogeneous forest cover. At the Belgian reactor BR1, situated in a forested environment, ambient gamma-dose-rate data from routine Ar-41 releases are available in the first 300 m from the release point.

Sensitivity and feedback of wind-farm induced gravity waves.

Flow blockage by large wind farms leads to an upward displacement of the boundary layer, which may excite atmospheric gravity waves in the free atmosphere aloft and on the interface between the boundary layer and the free atmosphere. In the current study, we assess the sensitivity of wind-farm gravity-wave excitation to important dimensionless groups and investigate the feedback of gravity-wave induced pressure fields on wind-farm energy extraction. The sensitivity analysis is performed using a fast boundary-layer model that is developed to this end.

Gravity Waves and Wind-Farm Efficiency in Neutral and Stable Conditions.

We use large-eddy simulations (LES) to investigate the impact of stable stratification on gravity-wave excitation and energy extraction in a large wind farm. To this end, the development of an equilibrium conventionally neutral boundary layer into a stable boundary layer over a period of 8 h is considered, using two different cooling rates. We find that turbulence decay has considerable influence on the energy extraction at the beginning of the boundary-layer transition, but afterwards, energy extraction is dominated by geometrical and jet effects induced by an inertial oscillation.

Dynamic dose assessment by Large Eddy Simulation of the near-range atmospheric dispersion.

In order to improve the simulation of the near-range atmospheric dispersion of radionuclides, computational fluid dynamics is becoming increasingly popular. In the current study, Large-Eddy Simulation is used to examine the time-evolution of the turbulent dispersion of radioactive gases in the atmospheric boundary layer, and it is coupled to a gamma dose rate model that is based on the point-kernel method with buildup factors. In this way, the variability of radiological dose rate from cloud shine due to instantaneous turbulent mixing processes can be evaluated.