Using observational mean-flow data to drive large-eddy simulations of a diurnal cycle at the SWiFT site

Reproducing realistic date- and site-specific unsteady wind conditions in large-eddy simulations is becoming increasingly useful in wind energy. How to run a large-eddy simulation to match observed conditions, however, remains an open research question. One approach that has received considerable attention is mesoscale-to-microscale coupling,...

Data-Driven Improvement of RANS Simulations of Wind Farms in Stable Atmospheric Boundary Layer Conditions

The most used RANS-model in relation to wind farms, k−epsilon, has significant shortcomings. It over-predicts the eddy viscosity in the near-wake and fails to model the anisotropy of the turbulence quantities. The Sparse Regression of the Turbulence Stress Anisotropy (SpaRTA) method could remedy these shortcomings. This method uses temporally...

Advancing Artificial Neural Network Parameterization for Atmospheric Turbulence Using a Variational Multiscale Model

Data-driven parameterizations offer considerable potential for improving the fidelity of General Circulation Models. However, ensuring that these remain consistent with the governing equations while still producing stable simulations remains a challenge. In this paper, we propose a combined Variational-Multiscale (VMS) Artificial Neural...

Modeling the atmospheric diurnal cycle

Weather and climate influence life in many ways; varying climatic conditions can be associated with varying human cultures and on a day-to-day basis, the weather influences our plans and mood. As such, a proper prediction of the weather is of great importance. Ultimately, the weather is fueled by solar irradiation, which changes sharply over the...

A simulation study on risks to wind turbine arrays from thunderstorm downbursts in different atmospheric stability conditions

Thunderstorm downbursts have been reported to cause damage or failure to wind turbine arrays. We extend a large-eddy simulation model used in previous work to generate downburst-related inflow fields with a view toward defining correlated wind fields that all turbines in an array would experience together during a downburst. We are also...

Complex terrain: from ruggedness index (RIX), towards physical parameterization

This thesis investigates terrain ruggedness characterization based on low-order terrain statistics. The statistics in question are the root-mean-square height and slope where the slopes are calculated both directly using the power spectral density and indirectly via a finite difference scheme. These statistics are, in contrast to the ruggedness...

Fifty Years of Atmospheric Boundary-Layer Research at Cabauw Serving Weather, Air Quality and Climate

An overview is given of 50-year Cabauw observations and research on the structure and dynamics of the atmospheric boundary layer. It is shown that over time this research site with its 200-m meteorological tower has grown into an atmospheric observatory with a comprehensive observational program encompassing almost all aspects of the...

A Three-Dimensional Array for the Study of Infrasound Propagation Through the Atmospheric Boundary Layer

The Royal Netherlands Meteorological Institute (KNMI) operates a three-dimensional microbarometer array at the Cabauw Experimental Site for Atmospheric Research observatory. The array consists of five microbarometers on a meteorological tower up to an altitude of 200 m. Ten ground-based microbarometers surround the tower with an array aperture...

On wind turbine loads during thunderstorm downbursts in contrasting atmospheric stability regimes

Severe winds produced by thunderstorm downbursts pose a serious risk to the structural integrity of wind turbines. However, guidelines for wind turbine design (such as the International Electrotechnical Commission Standard, IEC 61400-1) do not describe the key physical characteristics of such events realistically. In this study, a large-eddy...

River-induced anomalies in seasonal variation of traffic-emitted CO distribution over the City of Krasnoyarsk

Seasonal variation of air quality in a city with a large river was investigated by means of numerical simulations of air movement and pollutant dispersion over inversion-capped diurnal cycles using a Reynolds-averaged Navier-Stokes (RANS) approach with algebraic turbulent flux model. The study accounts for the effects of urban heat island ...

Towards Adaptive Grids for Atmospheric Boundary-Layer Simulations

We present a proof-of-concept for the adaptive mesh refinement method applied to atmospheric boundary-layer simulations. Such a method may form an attractive alternative to static grids for studies on atmospheric flows that have a high degree of scale separation in space and/or time. Examples include the diurnal cycle and a convective...

Performance of 3-D Surface Deformation Estimation for Simultaneous Squinted SAR Acquisitions

This paper addresses the performance in the retrieval of 3-D mean deformation maps by exploiting simultaneous or quasi-simultaneous squinted synthetic aperture radar (SAR) interferometric acquisitions in a repeat-pass scenario. In multisatellite or multibeam low earth observation missions, the availability of two (or more) lines of sight ...

Effects of atmospheric stability conditions on heat fluxes from small water surfaces in (semi-)arid regions

Atmospheric stability conditions over the water surface can affect the evaporative and convective heat fluxes from the water surface. Atmospheric instability occurred 72.5% of the time and resulted in 44.7 and 89.2% increases in the average and maximum estimated evaporation, respectively, when compared to the neutral condition for a small...

Antarctic boundary layer parametrization in a general circulation model: 1-D simulations facing summer observations at Dome C

The parametrization of the atmospheric boundary layer (ABL) is critical over the Antarctic Plateau for climate modelling since it affects the climatological temperature inversion and the negatively buoyant near-surface flow over the ice-sheet. This study challenges state-of-the-art parametrizations used in general circulation models to...

Energy Balance and Heat Storage of Small Shallow Water Bodies in Semi-arid Areas

This research aims at developing a flexible and efficient (numerical) approach for estimating energy balance and heat storage of small shallow lakes in arid and semi-arid regions. To reach to this aim, some numerical methods and improvements in conventional methods were done. Optimizing the methods developed in this thesis is considered in order...

To conserve, or not to conserve ...: Large eddy simulation of wind farms with energy-conserving schemes

This thesis concerns the industrial application of large eddy simulation to wind farm aerodynamics. Through a series of simple tests, it presents the pros and cons of using energy-conserving time integration and furthers the importance of a dissipation-free spatial discretisation. Finally, it demonstrates the capability of the Energy-Conserving...