An accurate method for the quantification of real-life driving rain loads on building envelopes from generally available climatic data such as wind speed, wind direc tion and horizontal rainfall intensity serves various purposes, from the development of de sign guidelines for building envelopes to the incorporation of driving rain loads as a boundary condition in Heat-Air-Moisture (HAM) transfer analysis models. In this paper, an existing numerical technique for driving rain simulation is incorporated into a practical nu merical method to estimate driving rain loads on building envelopes based on the building geometry and the climatic data at the building site. This numerical method is applied for sev eral sequences of spells around a low-rise test building and the results are experimentally verified. It is shown that the numerical method can accurately estimate the spatial and tem poral distribution of driving rain loads on building envelopes.
An experimental setup was designed for the purpose of validating a coupled CFD-diffusion model. In the CFD diffusion model, heat and mass transport in the air domain is solved using CFD, while, in the material domain, vapour transport is modelled using a control-volume vapour diffusion model. This CFD-diffusion model allows the prediction of the convective vapour transfer coefficient for developing momentum and moisture boundary layers. In the traditional vapour diffusion model, a convective vapour transfer coefficient is used. This model allows the indirect determination of the vapour transfer coefficient from experiments. The experiment consisted of a wind tunnel placed in an environmental chamber with climate control capability. The air flow in the wind tunnel was driven by a variable-control fan that allows for a range of speeds in the laminar regime. Convective vapour transfer coefficients were indirectly determined based on the experimenta measured moisture content changes in the material for a number of air speeds. The results were compared with CFD-diffusion model for the purpose of validation and sensitivity analysis.
The importance of aerodynamics in cycling is not a recent discovery. Already in the late 1800s it was recognized as a main source of resistance in cycling. This knowledge was only rediscovered in the late 1970s and 1980s, when aerodynamic concepts were applied to bicycle equipment and cyclist positions, leading to new world hour records and Olympic medals. The renewed interest for cycling aerodynamics is significantly growing with the production of a vast literature, focused on increasing the comprehension of cycling aerodynamics and on improving the aerodynamics of bicycle equipment. Finding the connection between the different subfields of cycling aerodynamics and linking new research with past discoveries is crucial to efficiently drive future studies. Therefore, the present paper provides a comprehensive review of the history and the state-of-the-art in cycling aerodynamics, focusing on one of its main aspects: the bicycle. First, a short history of the bicycle is presented. Next, some cycling power models are outlined and assessment methods for aerodynamic drag are discussed, along with their main advantages and disadvantages. The core of this review paper addresses the components constituting the bicycle: frame and tubes, wheels, handlebar and other equipment. Finally, some future perspectives on bicycle aerodynamics are provided.
High-resolution CFD simulations of forced convective heat transfer at the facades of a low-rise cubic building (10x10x10m³) are conducted to determine convective heat transfer coefficients (CHTC). CFD model validation is performed based on wind tunnel measurements of the upstream near-field velocity pattern. A particular feature of the CFD simulations is the use of a high-resolution grid with control volumes of only 160 micrometer near the building surfaces to resolve the entire boundary layer, including the laminar sublayer that dominates the convective surface resistance. The study shows that: (1) wind flow around the building introduces a very distinct CHTC distribution across the facade; (2) no significant correlation exists between the CHTC and the local wind speed across the facade; (3) for a reference wind speed of 3 m/s, the laminar sublayer has a thickness of about 1 mm; (4) standard and non-equilibrium wall functions are not able to capture the complexity of wind-induced heat transfer, therefore low-Reynolds number modelling on high-resolution grids is imperative; (5) the CHTC distribution across the windward facade shows some similarity to the distribution of wind-driven rain (WDR), with both parameters reaching high levels near the top edge of the facade. This suggests that also the convective vapour transfer coefficient will be higher at this location and that the facade parts that receive most WDR also experience most intensive drying.
Abstract High-fidelity two-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) simulations are employed to investigate the influence of boundary layer suction through a slot located near the leading edge of a vertical axis wind turbine operating in dynamic stall. The analysis includes both steady and unsteady suction with different frequencies. The results shows that: (i) when the suction slot is located within the chordwise extent of the laminar separation bubble, dynamic stall can be avoided with minimal suction amplitude; (ii) the most promising suction location is the most upstream suction location studied, at 8.5%c where c is the blade chord length; (iii) the suction only needs to be applied during the azimuthal angles when dynamic stall occurs; (iv) the oscillation frequency of the suction velocity has insignificant influence on the obtained turbine power gain; (v) applying unsteady suction is interesting as it reduces the energy consumption of the suction system, thus the net power gain.
