Abstract
Abstract. The present work analyzes the quality and reliability of an important class of general-purpose, second-order accurate finite-volume (FV) solvers for the large-eddy simulation of a neutrally stratified atmospheric boundary layer (ABL) flow. The analysis is carried out within the OpenFOAM® framework, which is based on a colocated grid arrangement. A series of open-channel flow simulations are carried out using a static Smagorinsky model for subgrid scale momentum fluxes in combination with an algebraic equilibrium wall-layer model. The sensitivity of the solution to variations in numerical parameters such as grid resolution (up to 1603 control volumes), numerical solvers, and interpolation schemes for the discretization of nonlinear terms is evaluated and results are contrasted against those from a well-established mixed pseudospectral–finite-difference code. Considered flow statistics include mean streamwise velocity, resolved Reynolds stresses, velocity skewness and kurtosis, velocity spectra, and two-point autocorrelations. A quadrant analysis along with the examination of the conditionally averaged flow field are performed to investigate the mechanisms responsible for momentum transfer in the flow. It is found that at the selected grid resolutions, the considered class of FV-based solvers yields a poorly correlated flow field and is not able to accurately capture the dominant mechanisms responsible for momentum transport in the ABL. Specifically, the predicted flow field lacks the well-known sweep and ejection pairs organized side by side along the cross-stream direction, which are representative of a streamwise roll mode. This is especially true when using linear interpolation schemes for the discretization of nonlinear terms. This shortcoming leads to a misprediction of flow statistics that are relevant for ABL flow applications and to an enhanced sensitivity of the solution to variations in grid resolution, thus calling for future research aimed at reducing the impact of modeling and discretization errors.
Highlights
Motivated by the aforementioned needs, the present study aims at characterizing the quality and reliability of an important class of second-order accurate FV solvers for the large-eddy simulation (LES) of neutrally stratified atmospheric boundary layer (ABL) flows
No apparent improvement was observed and the solution became very sensitive to grid resolution and matching location. This finding suggests that alternative procedures might need to be devised to overcome the log-layer mismatch (LLM) in ABL flow simulations when using the considered class of FV solvers
Note that profiles from the PSFD solver feature a positive LLM in spite of a spatial, low-pass filtering operation that is carried out on the horizontal velocity field before evaluating the surface shear stress (Bou-Zeid et al, 2005)
Summary
An accurate prediction of atmospheric boundary layer (ABL) flows is of paramount importance across a wide range of fields and applications, including weather forecasting, complex terrain meteorology, agriculture, air quality modeling, and wind energy (Whiteman, 2000; Fernando, 2010; Calaf et al, 2010; Oke et al, 2017; Shaw et al, 2019). Truncation errors corrupt the high wavenumber range of the solution, restricting the ability to adopt dynamic LES closure models that make use of information from the smallest resolved scales of motion to evaluate the SGS diffusion (Germano et al, 1991) Notwithstanding these limitations, central schemes have been heavily employed in the past in both the geophysical and engineering flow communities and are the de facto standard in the wind engineering community, where most of the numerical simulations are carried out using second-order accurate finitevolume (FV)-based solvers (Stovall et al, 2010; Churchfield et al, 2010; Balogh et al, 2012; Churchfield et al, 2013; Shi and Yeo, 2016, 2017; García-Sánchez et al, 2017; GarcíaSánchez and Gorlé, 2018). A further discussion on the sensitivity of the solution to model constants, interpolation schemes, and numerical solvers is provided in the Appendix
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