Measurement of air flow in duct by velocity measurements

To measure a flow in a closed duct, one of the available methods is to explore the velocity field. With this method, the quality of the flow measurement is very dependent on the location of the velocity measurement points in the duct section. Recommendations about velocity schemes are proposed in international standards (ISO 3966, ISO 7145, EN 12599 …) for circular and rectangular ducts. These recommendations assume that a turbulent flow profile is established. This requires flow profiler and/or long straight lengths upstream and downstream the measurement section. On site, these recommendations are difficult to apply strictly because conditions of straight lengths are often not available. Secondly, the velocity measurement schemes proposed in standards are often time consuming and users prefer sometimes to simplify them. In this case, the estimation of the measurement error is not known. A numerical study has been carried out to investigate the influence of the velocity measurement scheme on the flow measurement when the distance between disturbances and the measurement section is small in the case of circular and rectangular ducts. The results are presented in term of measurement error according to the shape of the duct, velocity scheme, number of velocity measurements, distance between disturbances and measurement section

Considering urban uses at a fine spatial resolution to understand the distribution of invasive plant species in cities

International audienc

How managers and city dwellers relate to spontaneous vegetation in cities: Towards an integrative approach

The promotion of spontaneous vegetation is recognized as a promising way to develop urban biodiversity atmultiple scales. However, enhancing spontaneous vegetation in highly anthropized spaces such as cities can leadto resistance from the various urban actors who plan, manage, and use the city. An integrated approachanalyzing the links between ecological, psychosocial, governance, and management issues is thus required. Herewe used complementary methods (focus groups, interviews) to analyze the relationships of municipal field operativesand city dwellers to spontaneous vegetation in the streets of a French medium-sized city. We show thatmunicipal elected officials and service director move towards a biodiversity-friendly strategy, but that themanagement system at all hierarchical levels must be engaged with to achieve a shared and collaborativetransition to sustainability. While field operatives are rather favorable to spontaneous vegetation, their practicesand their ability to change are highly dependent on psychosocial, organizational, and technical parameters thathave to be aligned with ecological objectives. Concerning city dwellers, the majority holds a positive view ofspontaneous vegetation, yet a considerable proportion of them seem indifferent to this vegetation. The provisioningof ecological information in situ (i.e., stickers with plant information on pavements) moderately improvestheir perceptions of spontaneous street vegetation. This educational approach should be accompanied byother approaches to amplify the effect for changing attitudes. These differing results are of timely interest to helpdevise and build an integrated socio-ecological system, and to find social and organizational levers to improvepeople–nature relationships in the city