the effects of wind in an urban areas Flashcards
How can winds be affected by urban areas
reduced by 30% due to increased frictional drag as obstructed by buildings
However, tall buildings can channel wind between narrow spaces creating a wind tunnel
How does an uneven surface area affect wind
varying heights of buildings exert a frictional drag which creates turbulence which results in rapid change in wind speed and direction
How do high rise buildings affect wind
although they can act as obstacles they can also channel air into canyons where winds are so powerful buildings can sway
How does the UHI affect wind
on calm clear nights when the UHI is greatest there will be an inflow from cooler areas into the city
How do single buildings affect air flow
modify air flow as air is displaced upwards and around the sides of the building and pushed downwards in the less
at windward side of building the air pushed against with high amounts of pressure
What happens as air flows around the sides of buildings
air becomes seperated from walls creating an area of suction
What happens on the windward side of the buidling
high pressure results in over pressure which increases with height, this results in a descending flow which forms a vortex at ground level causing wind to sweep around windward corners
What happens in the lee of the building
pressure decreases
What happens when there are 2 building
allow air flow between can result in venturi effect
What is the venturi effect
where pressure gaps cause wind speed to increase
What happens when the building is widely spaced apart
each building will act as an isolated block reducing the venturi effect
What happens if buildings are close together
each building interferes with the air flow around the next structure
