Wall-modeled lattice Boltzmann large-eddy simulation of neutral atmospheric boundary layers
Published paper in Physics of Fluids 33, 105111 (2021);"Wall-modeled lattice Boltzmann large-eddy simulation of neutral atmospheric boundary layers"
The lattice Boltzmann method (LBM) sees a growing popularity in the field of atmospheric sciences and wind energy, largely due to its excellent computational performance. Still, LBM large-eddy simulation (LES) studies of canonical atmospheric boundary layer flows remain limited. One reason for this is the early stage of development of LBM-specific wall models. In this work, we discuss LBM–LES of isothermal pressure-driven rough-wall boundary layers using a cumulant collision model. To that end, we also present a novel wall modeling approach, referred to as inverse momentum exchange method (iMEM). The iMEM enforces a wall shear stress at the off-wall grid points by adjusting the slip velocity in bounce-back boundary schemes. In contrast to other methods, the approach does not rely on the eddy viscosity, nor does it require the reconstruction of distribution functions. Initially, we investigate different aspects of the modeling of the wall shear stress, i.e., an averaging of the input velocity as well as the wall-normal distance of its sampling location. Particularly, sampling locations above the first off-wall node are found to be an effective measure to reduce the occurring log-layer mismatch. Furthermore, we analyze the turbulence statistics at different grid resolutions. The results are compared to phenomenological scaling laws, experimental, and numerical references. The analysis demonstrates a satisfactory performance of the numerical model, specifically when compared to a well-established mixed pseudo-spectral finite difference (PSFD) solver. Generally, the study underlines the suitability of the LBM and particularly the cumulant LBM for computationally efficient LES of wall-modeled boundary layer flows.
WAKE CONFERENCE, JUNE 15-17 2021
The bi-annual Wake Conference has gathered researchers within the field of wake interaction and flow modelling since more than ten years both on - and offshore. The conference is usually at Uppsala University Campus Gotland, which is located on the island of Gotland in the World Heritage city of Visby.
Organizers for the conference are Uppsala University (UU) and Technical University of Denmark (DTU). Professor Stefan Ivanell and Professor Jens Nørkær Sørensen.
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Webbinarium om den nationella vindkraftsstrategin (only in Swedish).
New project - Farmblockage, validation of model possibilities
Project leader: Stefan Ivanell, Uppsala University
Founding: Energy Agency
Due to the complexity, there is a lack of consensus in the industry in how blockage should be calculated. The models that are applied have varying ability to handle the different parts of the problem. The overarching goals of the project are to create an increased understanding of the underlying phenomena that create wind farm blockage. This includes identifying the most important effects, quantifying its potential impact on blockage, and evaluating the models and methods required to calculate expected blockage on a future wind farm.
This project will be of great importance to the industry's ability to assess third party calculations of blocking effects of which they are highly dependent and where there is great uncertainty today.
New project - Efficient handling of power system balance in a future with close to 100% renewable power
Project leader: Lennart Söder, Royal Institute of Technology
Founding: Energy Agency
Wind power has grown strongly in recent years and is expected to continue to increase significantly. Solar power is also expected to increase. In a power system, a continuous balance is maintained between production and consumption. In the Nordic power system, this is currently handled mainly by hydropower. With large amounts of wind and solar power, it will be a challenge to maintain this balance.
The system becomes more volatile with changing conditions between different states. Even in this system, the continuous balance between production and consumption must be maintained. At present, in 2020, there are several different support services for balancing, which affect each other: FFR, FCR, aFRR, mFRR, time shift trading etc.
The aim of this project is to estimate future imbalances and the need for support services. These will vary from hour to hour in a future, entirely renewable, electricity generation system. The basic system has much higher consumption, and more flexibility.
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