Performance analysis of wind fence models when used for truck protection under crosswind through numerical modeling

This paper is focused on truck aerodynamic analysis under crosswind conditions by means of numerical modeling. The truck was located on the crest of an embankment during the study. In order to analyze the performance of three wind fence models, the truck's aerodynamic coefficients were obtained and compared in two different situations either with or without the wind fences installed. In addition, the effect of both height and porosity of wind fence models on the aerodynamic coefficients acting on truck with respect to separation distance between the truck and the wind fence, was analyzed. A finite volume (or computational fluid dynamic) code was used to carry out the numerical modeling. The Reynolds-averaged Navier?Stokes (RANS) equations along with the k?? SST turbulence model were used to predict the behavior of turbulent flow. With respect to the results, the influence of the distance on the rollover coefficient is soft for all height values studied except for the lowest value (1 m of fence height), where the maximum value of rollover coefficient was obtained for the truck position closer to the fence. Regarding fence porosity, its effect on rollover coefficient is stronger for truck positions on road closer to the wind fence model.This work was supported by the OASIS Research Project that was co-financed by CDTI (Spanish Science and Innovation Ministry) and developed with the Spanish companies: Iridium, OHL Concesiones, Abertis, Sice, Indra, Dragados, OHL, Geocisa, GMV, Asfaltos Augusta, Hidrofersa, Eipsa, PyG, CPS, AEC and Torre de Comares Arquitectos S.L. and 16 research centres. The authors would also like to thank the GICONSIME research group of the University of Oviedo (Spain) for their collaboration in this research

Aerodynamic roughness parameters in cities: inclusion of vegetation

A widely used morphometric method (Macdonald et al. 1998) to calculate the zero-plane displacement (zd) and aerodynamic roughness length (z0) for momentum is further developed to include vegetation. The adaptation also applies to the Kanda et al. (2013) morphometric method which considers roughness-element height variability. Roughness-element heights (mean, maximum and standard deviation) of both buildings and vegetation are combined with a porosity corrected plan area and drag formulation. The method captures the influence of vegetation (in addition to buildings), with the magnitude of the effect depending upon whether buildings or vegetation are dominant and the porosity of vegetation (e.g. leaf-on or leaf-off state). Application to five urban areas demonstrates that where vegetation is taller and has larger surface cover, its inclusion in the morphometric methods can be more important than the morphometric method used. Implications for modelling the logarithmic wind profile (to 100 m) are demonstrated. Where vegetation is taller and occupies a greater amount of space, wind speeds may be slowed by up to a factor of three

강제환기식 돈사의 환기 효율성 분석을 위한 CFD 모델 개발

When livestock facilities in Korea have been changed larger and denser, rearing conditions have been getting worse and the productivity of animal production have been decreased. Especially in the cold season, the minimized ventilation has generally been operated to save energy cost in Korea resulting in very poor environmental condition and high mortality. While the stability, suitability, and uniformity of the rearing condition are the most important for high productivity, the ventilation configuration is the most important to improve the rearing condition seasonally. But, it is so difficult to analyze the internal air flow and the environmental factors by conducting only field experiment because the weather condition is very unpredictable and unstable as well as the structural specification can not be easily changed by the researchers considering cost and labor. Accordingly, an aerodynamic computer simulation was adopted to this study to overcome the weakness of conducting field experiment and study the aerodynamic itself. It has been supposed that the airflow is the main mechanism of heat, mass, and momentum transfers. To make the simulation model accurately and actually, simplified pig models were also developed. The accuracy of the CFD simulation model was enhanced by 4.4 % of errors compared with the data collected from field experiments. In this paper, using the verified CFD model, the CFD computed internal rearing condition of the mechanically ventilated pig house were analyzed quantitatively as well as qualitatively. Later, this developed model will be computed time-dependently to effectively analyze the seasonal ventilation efficiency more practically and extensively with tracer gas decay theory