Sensibilidade de parâmetros de um modelo de cálculo para a simulação do ambiente acústico urbano

The applicability of the French model NMPB Routes 2008 for the simulation of the urban environmental noise in a Brazilian city is brought up in this paper, considering an analysis of the model sensitivity to the input parameters. For this purpose the calculation model is applied in an urban zone of the city of São Carlos - SP, by means of the software Cadna-A. The analysis compared field data and simulated data. Additionally simulations were processed, changing some input data configuration. The parameters verified with the sensitivity analysis were the meteorological conditions, the duration of the period of vehicular flow collection, the percentage of motorcycles in fields of light vehicles and heavy vehicles, the vehicular speed, the pavement type, the road declivity and direction of vehicular flow, the heights of the buildings and of receptors, the sound source type, and the quantity of sound sources per road. But for the meteorological conditions, the results proved that the model is sensible to the most part of the analyzed parameters. There is, however, an indication that some input fields could be adjusted to precisely fit to real data.A aplicabilidade do modelo de cálculo francês NMPB Routes 2008 para simulação do ruído ambiental urbano em uma cidade brasileira é abordada nesse artigo, considerando-se uma análise da sua sensibilidade aos parâmetros de entrada. Para isso o modelo de cálculo é aplicado em uma fração urbana da cidade de São Carlos - SP, através do programa computacional Cadna-A. A análise comparou dados de campo e dados simulados, além de serem realizadas simulações promovendo-se alterações nas configurações dos dados de entrada. Os parâmetros verificados com a análise de sensibilidade foram as condições meteorológicas, a duração do tempo de amostra do fluxo de veículos, a porcentagem de motocicletas em campos destinados ao número de veículos leves ou de veículos pesados, a velocidade dos veículos, o tipo de pavimentação, a declividade da via e a direção de fluxo de veículos, as alturas dos edifícios e as alturas de receptores, o tipo de fonte sonora e a quantidade de fontes sonoras inseridas por vias. Com exceção das condições meteorológicas, os resultados apontaram que o modelo, de uma forma geral, é sensível à maioria dos parâmetros analisados. Observou-se, no entanto, que alguns campos podem ser ajustados para que a simulação seja mais fidedigna aos dados reais.Palavras-Chave: simulação acústica, mapeamento de ruído, parâmetros acústicos, conforto acústico

VERIFICATION OF THE INFLUENCE OF URBAN GEOMETRY ON THE NOCTURNAL HEAT ISLAND INTENSITY

Nocturnal heat island formation is a prom inent phenomenon in urban planning research and thermal comfort. It is characterized by an increased air temperature from the periphery to the center of the cities and is partly caused by the urban geometry. The phenomenon is a result of the influence of the characteristics of urbanization, which alter the energy balance of the cities. Among surveys in this context, the model proposed by Oke (1981) shows its relevan ce in the area. Using simulations with reduced models, Oke found that the fraction of visible sky negatively correlated with the heat buildup on the surfaces and increased the air temperature. The relationship between the height of the buildings and the width of the path (H/W ratio, height/width) was used to measure the urban geometry in this previous study. Based on that study, this research verified the role of geometry in the formation of an urban heat island in a Brazilian city, aiming to adapt this model to real urban conditions. The methodological procedures rely on the following steps: a study of a theoretical-numerical base model (Oke model, 1981) and adjustment (validati on). Thus, the methodology to be employed included urban data collection, which include d urban geometry and air temperature, the application of the Oke model and its adjustme nt. The results found in this investigation corroborate the study of Oke (1981) and dem onstrate that urban geometry effectively contributes to the formation of nocturnal heat islands