Concordia Corner

Wind tunnel offers answers about which way the wind blows

Karen Herland

Once everything is in place, the laser allows researchers to see the wind move through a structure to test possibilities for natural ventilation.

Photo by Rob Maguire

Buildings account for 30 per cent of greenhouse gas emissions generated in Canada, while a third of the energy and more than 50 per cent of the electricity consumed are used in buildings.

There’s a growing concern for the energy efficiency of buildings, according to Panagiota Karava, a building and civil engineering PhD student.

Her graduate research is aimed at developing more efficient natural or hybrid ventilation systems that use natural forces, including wind and thermal buoyancy, for a comfortable interior climate.

Karava has been studying these principles since her undergraduate degree. As a master’s student, she used them to contribute to the design of the EV Building. Her doctoral work takes that research further. She is calculating the best placement of openings (windows, vents, etc.) in buildings to maximize the natural ventilation.

To do so, she is using the wind tunnel deep in the second sub-basement of the building she helped design. The tunnel was built by now-retired technician Hans Obermeyer according to Professor Ted Stathopoulos’s specifications. It is it the only one in the province of its kind, and was designed to best represent real conditions. The impressive 12-metre-long structure dominates the room it occupies.

Usually, such machines are used to determine the effect of wind pressure and all other interactions between wind and buildings on the urban environment

The tunnel is surrounded by numerous scale models of parts of Montreal — like the south edge of the mountain along Pine Ave., or the Quartier Concordia campus with a model of the proposed JMSB building across Guy St. from its EV building twin.

These models are used to determine how urban topography interacts with wind flow. The research can influence the way a building is structured to withstand the specific pressures it might be subjected to or to avoid the re-ingestion of contaminants.

Karava’s ventilation research is unique. Her experiment measures the wind’s movement through and around a building model while varying the placement and design of openings on the facade. She disperses particles (in this case, smoke) at her model, with the wind force directed at it. Using a laser, she can illuminate the particles, which reflect the light. The effect is recorded by a camera located above the building model that takes photographs in quick succession. In short, she is photographing the wind.

“There are a lot of variables — the type and density of particles, the intensity of the light-sheet, and the wind itself,” Karava said.

The camera’s data are transmitted to a computer that calculates the wind’s movement by tracking the speed and path of the particles around it. The technique is called particle image velocimetry.

Karava is working under the supervision of Professors Stathopoulos and Andreas Athienitis. She hopes to complete her research by the end of the year.