A TEMPLATE MATCHING-BASED METHOD FOR IDENTIFYING THE SEPARATION POINT OF BUOYANT WALL JETS

International audienceA cold air jet introduced just below a horizontal wall attaches to the wall and then separates from it. The distance between the separation point and the inlet nozzle is an important design parameter for air conditioning systems. Using laser-light sheet visualization, the separation point can be located by either visual observation or image processing. Nevertheless, the unsteadiness of the separation point, induced by the turbulence of the jet, requires tens or hundreds of readings for one determination, making visual measurement tedious and hardly reproducible. As an alternative, the separation point of the jet from the wall may be numerically located where the highest correlation between the image of the jet edges and the template representing the characteristic separation pattern is found in the image. The correlation, calculated using the Discrete Fourier Transform, also gives a measure of the separation point location clarity

Monitoring the effect of urban green areas on the heat island in Athens

The role of urban green areas in the microclimatic conditions of cities, during summer, is investigated in this paper through monitoring campaigns carried out at the National garden, at the city centre of Athens. Two types of investigations were carried out: i) a microscopic one that investigated the thermal conditions inside the Garden and the immediate surrounding urban area and ii) a macroscopic one that compared the temperature profile of the Garden with that of the greater city centre area. It was concluded that in microscopic level, the temperature profile inside the National Garden and the immediate surrounding urban area did not showed a clear evidence of the influence of the Garden and it was dependent on the characteristics of each location. In a macroscopic scale, the Garden was found cooler than the other monitored urban locations and temperature differences were mainly greater during the night, especially in streets with high building height to street width (H/W) ratio and low traffic, while in streets with high anthropogenic heat during the day, the biggest temperature differences were recorded during the day