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This study evaluates the uncertainty in speed-up factors predicted using the Reynolds-Averaged Navier-Stokes equations to model flow over moderately complex forested terrain and considers its effect on the uncertainty in wind energy calculations. All simulations are solved using the open-source software openfoam v.2.4.0 with a modified k-e turbulence closure. The forest drag effect is calculated with two models: a displacement height model and a canopy model that estimates the pressure loss due to the forest through analogy with porous media. Two years of concurrent wind data from three meteorological masts at a potential wind farm site in Canada are used for validation purposes. In all, these experimental data are compared with the predictions of four wind flow models: (A) a terrain only model, (B) a displacement height model, (C) a uniform forest canopy model, and (D) a non-uniform forest canopy model. Overall, the canopy models provide better agreement with the mean statistical results than the displacement height model. In this case, the 2.76% uncertainty in the speed-up factor associated with the wind flow predictions of the non-uniform forest distribution model leads to an uncertainty in the energy calculation of just 5.94%. [ABSTRACT FROM AUTHOR]

Wind loading on lattice structures is studied locally by considering the applied forces on individual angle members. This work represents a comprehensive Computational Fluid Dynamics (CFD) analysis of wind loading on angle members, which includes a quantitative evaluation of the aerodynamic drag and lift loading and also a qualitative investigation of the wake characteristics behind the angle member. The focus is on the flow around the angle member cross-section which has two equal length sides at a right angle to each other. CFD has been used to investigate the flow around a single angle member characterized by its length D , thickness T , and angle of incidence to the oncoming flow. Both Reynolds-Averaged Navier–Stokes (RANS) and Large-Eddy Simulation (LES) are evaluated for a Reynolds number of 37,700, where the k- ϵ RANS and Wall-Adapting Local Eddy-viscosity (WALE) LES models are respectively used. The results are compared with the wind tunnel experiments reported in the literature (Wardlaw, 1967; Slater, 1969; Prud'homme et al., 2014) and the National Building Code of Canada (Canadian Commission on Building and Fire Codes and National Building Code of Canada, 2005), where the drag and lift coefficients at a range of incidence angles were reported. Quantitatively, the RANS performs well when compared to experiments for the aerodynamic coefficients at a range of incidence angles and less well for angles where a cavity style flow is formed and the separation becomes influential. This is in contrast to other bluff body cases where RANS does not perform so well. The LES is thus run at selected incidence angles for comparison and to better understand the flow where the RANS performs well and less well. Details of the turbulence in the wake are difficult to interpret when using RANS modeling, but this behavior is well illustrated with the LES model and details are reported here. • Evaluation of the aerodynamic drag and lift loading on angle members. • Investigation of the wake characteristics behind the angle member. • Both RANS and LES are evaluated for a Reynolds number of 37,700. • RANS performs well againt litterature at a range of incidence angles. • LES better understand the flow where the RANS performs less well. • This study constitutes a basis for evaluating the mask effect over multiple members. [ABSTRACT FROM AUTHOR]

A simulation methodology is introduced to provide improved estimates of the true efficiency gains that can be achieved using aerodynamic drag-reduction technologies for ground vehicles, with a particular application to heavy-duty-vehicle operations. The approach is based on a stochastic simulation methodology that applies route-specific wind conditions to predefined duty cycles, using wind-climate data calculated from publicly-accessible data sets. The simulation tool accounts for vehicle duty-cycle, seasonal wind conditions, the direction of travel, and diurnal effects to generate resultant-velocity and yaw-angle predictions along a specified route. Aerodynamic drag and associated fuel-use predictions are then made based on vehicle aerodynamic performance models generated from sources such as wind-tunnel measurements, road/track measurements, or computational fluid dynamics (CFD) simulations. The simulation software was used to evaluate the benefits of drag-reduction technologies associated with heavy-duty vehicles (HDV) travelling at low speeds on two major routes in Canada. The fuel-savings rate was determined for several drag-reduction technologies and tractor-trailer-height-matching approaches on two highway routes, and at vehicle ground speeds of 50 ​km/h, 80 ​km/h, and 100 ​km/h. This approach provides a representative range of fuel savings that considers the effect of different wind climates on the performance of the drag-reduction strategies. The results suggest that drag-reduction technologies, and particularly height-matching approaches, can have important contributions to reducing fuel use and the associated greenhouse gas emissions at speeds as low as 50 ​km/h. Vehicle weights ranging from 13,600 ​kg (30,000 lb) to 54,500 ​kg (120,000 lb) were evaluated to identify the relative contributions of rolling resistance and aerodynamic drag on a vehicle's total fuel consumption. Although the proportion of a vehicle's total fuel consumption from aerodynamics is reduced at low speeds, the fuel savings that can be achieved with standard drag reduction approaches can provide a meaningful reduction in fuel use, a reduction in fuel costs, and a reduction in greenhouse gas emissions. • Drag-reduction technologies and proper height-matching can result in meaningful fuel savings at 50 to 60 km/h. • Route-specific software provided higher-fidelity fuel savings predictions than conventional methods • Drag due to rolling resistance was the dominant contributor to fuel consumption for a vehicle weight of 54,500 kg. • The proportion of fuel consumption due to aerodynamic effects was greater above 80-90 km/h. [ABSTRACT FROM AUTHOR]