Abstract
Accurate and reliable Computational Fluid Dynamics (CFD) simulations of wind flow over natural complex terrain are important for a wide range of applications including dispersion of pollutants, wind energy resource assessment and ship manoeuvring in channels and near harbours. In the past 50 years, a very large number of CFD studies of wind flow over hills have been performed. However, a detailed review of the literature shows a lack of CFD studies including validation by field measurements for natural complex terrain beyond the case of isolated hills. Therefore, this paper presents a CFD study with field measurement validation for natural complex terrain that consists of an irregular succession of hills and valleys surrounding a narrow entrance channel. The aim of the study is twofold: (1) to evaluate the accuracy of 3D steady Reynolds-averaged Navier–Stokes (RANS) simulations with a revised k–ε model for calculating mean wind-velocity patterns over this type of natural complex terrain; and (2) to provide mean velocity data that can be used as input for real-time ship manoeuvring simulations to evaluate accessing the LNG terminal with larger LNG carriers. The irregular hilly terrain is expected to yield complex wind environmental conditions in the channel and complex forces on the LNG carriers. The study focuses on high wind speed conditions, for which the atmospheric boundary layer exhibits neutral stratification. The simulations are performed with 3D steady RANS and the realisable k–ε model for 12 wind directions. Special attention is given to surface roughness parameterisation and specification. The simulation results of mean wind speed and wind direction are generally within 10–20% of the corresponding measurement values. The results show that for wind directions 60° and 90°, the funnelling effect leads to an increase of wind speed in the channel compared to the wind speed over open sea. For other wind directions, the topography leads to a reduction of the wind speed in the channel, but also to strong wind speed gradients along the channel axis, which are important for ship manoeuvring. The study shows that for the present application, the 3D steady RANS approach with the realisable k–ε model can provide an accurate assessment of the complex mean wind-flow patterns and the funnelling effect by the natural complex topography on the wind.
Highlights
The study of wind flow over hills, valleys and other types of complex topography is important for many wind engineering applications, including dispersion of pollutants (e.g. Dawson et al 1991, Apsley and Castro 1997a, 1997b, Ohba et al 2002), wind energy resource assessment (e.g. Taylor and Teunissen 1987, Palma et al 2008, Conan et al 2012, Chaudhari 2014) and ship manoeuvring in harbours
Because of the lack of Computational Fluid Dynamics (CFD) studies validated with field measurements for natural complex terrain beyond the case of the isolated hill and because of the above statements on Reynolds-averaged Navier-Stokes (RANS) versus LES, this paper addresses the need for RANS simulations with field measurement validation for natural complex terrain consisting of an irregular succession of hills and valleys
Accurate and reliable Computational Fluid Dynamics (CFD) simulations of wind flow over natural complex terrain are important for a wide range of applications including dispersion of pollutants, wind energy resource assessment and ship manoeuvring in channels and near harbours
Summary
The study of wind flow over hills, valleys and other types of complex topography is important for many wind engineering applications, including dispersion of pollutants (e.g. Dawson et al 1991, Apsley and Castro 1997a, 1997b, Ohba et al 2002), wind energy resource assessment (e.g. Taylor and Teunissen 1987, Palma et al 2008, Conan et al 2012, Chaudhari 2014) and ship manoeuvring in harbours. Raithby et al 1987), which are more suitable for cases with flow separation, as flow separation is a process that involves dominant non-linear mechanisms Most of these nonlinear studies, published in the past 30 years, focused on 2D or 3D generic/idealized isolated hills or sometimes on successions of idealized hills, often with validation by reduced-scale wind-tunnel measurements. These should be acquired over a sufficiently long time period because of the intrinsic variability of meteorological conditions (Schatzmann and Leitl 2011) Because of this focus, the section presents a brief summary of a detailed literature review on CFD studies for wind flow over natural complex terrain including validation with field measurements.
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