Corresponding Author:
Wind resource and wind safety assessment in an urban
complex
N. Garg
1
, and N. Srikanth
2
1
Energy Research Institute, Nanyang Technological University (
Singapore
)
2
Energy Research Institute, Nanyang Technological University (
Singapore
)
A
BSTRACT
This work evaluates the wind resource and wind safety
in an urban complex. The present work uses field studies
and computational assessment for conducting a detailed
study. A 3D model of urban complex is made from GIS
data using ArcGIS and CAD tool whereas computational
studies are conducted using ANSYS Fluent 14. The
results show complex wind flows in different regions of
urban complex, which include but not limited to, distinct
recirculation zones on building rooftops and behind the
buildings. It is noteworthy that the wind flows are
dominated by the orientation of buildings, aspect ratio of
buildings, spacing between the buildings, and variable
building heights. These factors lead to induced swirling
flows, resulting in flow channelling thereby creating high
and low wind speed zones. By successfully implementing
both computational and experimental methods, this work
highlights the inadequacies of conventional techniques
for wind assessment in urban complex and the need for
improved assessment of pedestrian comfort vis-a-vis the
increased rate of construction.
Keywords: Complex terrain, Computational Fluid
Dynamics, GIS, Urban wind resource, Wind safety
I
NTRODUCTION
Since energy production is no longer limited to
decentralized system and brought into the urban
environment, where bulk of energy consumption takes
place, new technologies are emerging while existing
technologies are used in different contexts. One of these
technologies is wind energy. Even though it is very well
known that wind energy in urban cities is lower, several
tests are being conducted in different countries to conduct
feasibility studies. With the advent of modern
manufacturing techniques, there’s a possibility for new,
cost-effective wind turbine designs. The prominent
configurations for urban wind turbines are wind and solar
hybrid system, rooftop mounted and building integrated
wind turbine. One essential part of wind energy
integration in an urban complex is accurate wind resource
assessment and turbine siting.
Day to day experiences, wind tunnel studies, and
Computational Fluid Dynamics (CFD) simulation have
led to a common knowledge that the wind speed increases
in the passages between the buildings.
Wind comfort and wind safety are equally important
requirements for urban areas. The wind comfort and
safety generally refer to mechanical effects of wind over
people [1]. In particular, near high rise buildings, high
velocities are often introduced at pedestrian level that can
be uncomfortable or even hazardous. The two main
classifications of wind comfort and safety study are (1)
fundamental studies, using regular shaped complex and
(2) applied studies, conducted on actual test cases which
provide information for wind environmental condition in
specific case studies. Studies such as wind tunnel
measurement which is conducted within multiple
building arrangements as shown in [2, 3] and CFD
modelling studies as conducted in [4, 5] showed that
amplification factor up to 1.4 has been reported in
passage centreline. Amplification factor is the ratio of
mean wind speed at a location to the mean wind speed
without the buildings present. The urban authorities in
numerous cities nowadays recognize the importance of
pedestrian wind comfort and require such studies before
any new construction.
Wind resource assessments are commonly carried out
using a conventional anemometer (cup/ ultrasonic)
installed on a mast/pole. This technique is deemed to be
the most accurate method for wind measurement although
it has its own limitations. A typical wind measurement
campaign consists of a mast with height between 30 to
125 metres, located in open terrain or in open waters.
Measurements carried out at such locations would be
limited to surrounding area, the size of which depends on
factors as per [6]:
Shelter from nearby obstacles
Effect of roughness and roughness changes
Effects of topography over a scale of few
kilometres
Thermally driven flows
The wind measurements are site specific and variation
in measurement could be of several orders of magnitude,
depending on factors such as terrain roughness and
sheltering. The terrain roughness is described as the
various unique features of any specific location such as
open grass lands, open sea, suburban areas, and city
centres. Around the world, past wind resource assessment
studies have been conducted in complex locations[7],
namely, cities, but the data collection has been found
insufficient or are limited to small areas due to the
instabilities and flow variation present. Using CFD
simulations, wind flow over an urban complex can be
modelled. The drawback associated with this technique is
uncertainties vis-à-vis the CFD modelling. The
methodology for computational assessment of wind
resource in an urban complex and pedestrian comfort is
presented in this paper. This study also highlights the
methodology for Atmospheric Boundary Layer (ABL)
2013 International Conference on Alternative Energy in Developing Countries and Emerging Economies
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