Abstract:
This study investigates the wind flow and turbulence characteristics in and above an urban street
canyon in Akure City Centre, Southwest Nigeria. The data used for this study were obtained
between June 2013 – December, 2013 in the street canyon bordered by the Akure Central Mosque
to the north and the Oja-Oba (Oba’s Ultra-Modern Market) to the south on Oba Adesida road,
Akure with height to width ratio H/W = 12/30. Wind speed and direction were simultaneously
monitored on a lamppost in the middle of the road at two levels ( in-street, 3m and roof level, 12m)
within and above the canyon, using RM Young wind sentry cup-anemometer and wind vane
system . Traffic count was also taken using a digital traffic counter. Data analysis was carried out
using descriptive statistics in Microsoft excel.
Flow channeling, recirculation and helical vortices (spiraling) are identified in the canyon for along
street (220ᵒ - 250ᵒ), across street (190ᵒ - 170ᵒ) and oblique (120ᵒ - 150ᵒ), roof level flows.
Turbulence kinetic energy and turbulence intensity are also observed to be strongly dependent on
the roof-top wind direction within the canyon. Turbulence kinetic energy and wind speed decrease
within the canyon for across street roof-top flow, while turbulence intensity increases within and
above the canyon. Small changes in roof-level wind direction are found to have profound
influences on the behavior of in-street flow patterns. Consequently, variability in background flow
direction can lead to highly scattered in-street mean flow. Flow disturbance by vehicular traffic
also appears to increase the flow complexity for low wind conditions
