Some effects of crosswind on ventilators: Fid-Bau Portal

Some effects of crosswind on ventilators

Ghosh, B.K.

AbstractEffect of crosswind on simulated natural smoke ventilators have been studied in a 1/5th scale model using alcohol fires to produce the buoyant gas flow and a simple “wind tunnel” to provide the crosswind. The results indicate that the effect of crosswind on the discharge coefficient of ventilators depends on the temperature and the thickness of the hot gas layer below the ceiling, ventilator geometry and the airspeed.In general, the effect due to crosswind is more pronounced for cool, “shallow” gas layers; “thick” hot gas layers have higher buoyancy, which reduces any wind effect.For a ventilator with a kerb around its perimeter, crosswind may actually improve the performance, whereas there is a significantly adverse wind effect when no kerb is present. Thus for a well designed ventilator, crosswind should have a beneficial effect.It was also found that in some tests with “cool”, shallow layers, the discharge coefficients at no wind was low. This may be due to the flow becoming transitional (from turbulent) or due to an internal crossflow reducing the effective discharge coefficient.