wind microclimate assessment

Revision 1 – 19-Jun-2014 Prepared for – University of Newcastle – ABN: 15 736 576 735

University of Newcastle NeW Space University of Newcastle 19-Jun-2014

Commercial-in-Confidence

Wind Microclimate Assessment Pedestrian comfort at the University of Newcastle NeW Space

AECOM University of Newcastle NeW Space Wind Microclimate Assessment Commercial-in-Confidence


Wind Microclimate Assessment Pedestrian comfort at the University of Newcastle NeW Space

Client: University of Newcastle

ABN: 15 736 576 735

Prepared by AECOM Australia Pty Ltd Level 9, 8 Exhibition Street, Melbourne VIC 3000, Australia T +61 3 9653 1234 F +61 3 9654 7117 www.aecom.com ABN 20 093 846 925

19-Jun-2014

Job No.: 60315005

AECOM in Australia and New Zealand is certified to the latest version of ISO9001, ISO14001, AS/NZS4801 and OHSAS18001.

© AECOM Australia Pty Ltd (AECOM). All rights reserved.

AECOM has prepared this document for the sole use of the Client and for a specific purpose, each as expressly stated in the document. No other party should rely on this document without the prior written consent of AECOM. AECOM undertakes no duty, nor accepts any responsibility, to any third party who may rely upon or use this document. This document has been prepared based on the Client’s description of its requirements and AECOM’s experience, having regard to assumptions that AECOM can reasonably be expected to make in accordance with sound professional principles. AECOM may also have relied upon information provided by the Client and other third parties to prepare this document, some of which may not have been verified. Subject to the above conditions, this document may be transmitted, reproduced or disseminated only in its entirety.



Quality Information Document Wind Microclimate Assessment

Ref

60315005

p:\60315005\6. draft docs\6.1 reports\140617 lyons - planning reports - final\140619 uon new space environmental impact statement - wind microclimate report [1].docx

Date 19-Jun-2014

Prepared by Nicki Parker

Reviewed by Simon Evans

Revision History

Revision Revision Date Details

Authorised

Name/Position Signature

0 06-Jun-14 Draft For Comment Steve Agnew Technical Director

1 19-Jun-2014 Final Steve Agnew

Technical Director



Table of Contents Executive Summary i 1.0 Introduction 1

1.1 Urban wind effects 1 1.2 Purpose, basis and limitations of this report 1 1.3 Focus of this report 1

2.0 Assessment criteria 2 2.1 Basis 2 2.2 Comfort 2

3.0 The local wind climate 3 3.1 Meteorological data 3 3.2 Summary statistics 3

4.0 Comfort assessment 5 4.1 Wind-sensitive locations 5 4.2 Corner of Auckland Street and Hunter Street 5 4.3 Courtyard 5 4.4 Urban rooms 6

5.0 Conclusion 7 5.1 Likelihood of discomfort 7 5.2 Mitigation 7

References 8 Appendix A

Proposed Landscape Design A



i

Executive Summary This report assesses the likelihood that wind-induced discomfort may be felt by patrons of various outdoor spaces around the University of Newcastle’s NeW Space. The assessment draws on a large local meteorological data set adjusted for location and height.

Winds are assessed against a modified Lawson set of criteria, which sets upper wind speeds for comfort during a range of typical activities — long-term sedentary (e.g. sitting at café tables), short-term sedentary (e.g. queuing, talking), slow movement (e.g. window shopping, strolling), and rapid movement (e.g. fast walking).

Winds were analysed:

- for all hours of the day and in any season

- for business and commuting hours in any season

- for business and commuting hours in winter.

The two latter cases provide a picture of wind effects when most patrons are present. The winter scenario is included because the risk of discomfort is typically greater at this time (although patronage of outdoor spaces is typically lower).

A summary of the assessment is shown in the table below. The greatest risk is to the courtyard area and the walkway between NeW Space and University House. The courtyard is likely to experience similar conditions to those currently experienced in Civic Park and Christie Place. With the inclusion of the proposed landscape plan, elevated wind speeds are likely to be reduced. The walkway between NeW Space and University House may be prone to north westerly winds funnelling through between the buildings. As this is a transition space, no mitigation measures are proposed as it is unlikely pedestrians will be spending extended periods of time here.

Summary of findings. Crosses indicate a substantial risk of discomfort, diamonds indicate that occasional discomfort may occur, and ticks indicate that discomfort is unlikely.

Risk level

Area Activity Type All hours & seasons

Business hours, all seasons

Business hours, winter

Corner of Auckland and Hunter Streets

Long-term sedentary Short-term sedentary Slow movement Rapid movement

Courtyard Long-term sedentary Short-term sedentary Slow movement Rapid movement

Urban Rooms Long-term sedentary Short-term sedentary Slow movement Rapid movement

Walkway between NeW Space and University House

Long-term sedentary Short-term sedentary Slow movement Rapid movement



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1.0 Introduction

1.1 Urban wind effects Air flow around, over and through buildings must negotiate large obstructions, sharp corners, and narrow openings. As a result, air flow patterns in the built environment are typically complex, and may feature recirculation zones, rapidly rising or falling flows, and regions of stagnation.

Building downwash may be due to the blocking effect of large buildings, whereby wind impacting on the building is partially directed downward. On the lee side, downwash is due to the formation of a recirculation zone behind the building, which in turn forms a downward stream some distance downwind. Downwash may result in accelerated wind speeds at pedestrian level. These effects are influenced by factors including building form and orientation.

Horizontal steering can be caused by flow-stream compression through the gaps between buildings (the ‘street-canyon effect’), building downwash and corner acceleration. Horizontal vortices may contribute to unpleasantly high wind speeds, and gusty wind conditions at street level. Horizontal wind effects are influenced by a range of factors including building form, placement and orientation, local topography, and nearby buildings.

The most common complaints are of high wind speeds in particular areas; doors and other openings consistently exposed to wind; dirt or spray pickup; and building alignments which favour hot summer winds, cold winter winds, or stagnation. These encompass both the mechanical effect of wind and its thermal effect on people.

Local authority planning guidelines typically focus on user comfort and safety. Here, users are usually taken to be at ground level (or the main podium etc. level) of a particular space. They may be passing through on foot or bicycle; wandering slowly (e.g. window shopping); sitting or standing for a short period (e.g. at a bus stop or kiosk) or for a long period (e.g. outdoor dining). Planning criteria focus on the frequency of high winds, which are known to be uncomfortable in various situations and for various durations of exposure.

Upper-level users of balconies etc. may also be affected by winds, but exposure is generally considered to be by choice and easily avoidable. In rare cases, outdoor dining or other regular outdoor activity may take place relatively high above ground level, in which case special assessments must be made.

1.2 Purpose, basis and limitations of this report The purpose of this report is to provide evidence as to the likelihood of wind-induced discomfort to ground-level users of the spaces around the building.

This report presents probabilistic estimates of the likelihood of events which may have comfort implications. These are based on historical wind data and measured against commonly available wind effects criteria using accepted estimated methods. Given these limitations, AECOM cannot guarantee with certainty that the development will not adversely impact upon safety and comfort in the public realm.

This report is based on drawings and other information supplied; a statistical analysis of data; published methodologies for wind assessment; and specialist knowledge. The statistical analysis does not include an allowance for rare high-wind events such as severe storms. Also note that future wind patterns may not reflect past wind patterns. For example, changes in wind climate due to global warming are not accounted for. This report does not address structural aspects of wind phenomena.

All advice is provided with best intent and to the accuracy limits of the nature of the assessment undertaken.

1.3 Focus of this report Wind effects typically in need of mitigation are those encountered by individuals in outdoor or semi-outdoor spaces. Consequently, this report focuses on the likely extent of these effects, if any. Other issues such as wind blowing into doorways, lifting dirt etc., will be discussed if they are considered significant.



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2.0 Assessment criteria

2.1 Basis Wind speed and gustiness are the primary measurable factors affecting people. Other factors such as air temperature and humidity, clothing, sun exposure, etc. are also significant, but these can often be addressed by a modification of effective wind speeds (Twidell, 2006).

Wind speed is understood to mean the average wind speed taken over a time of one hour or so. Gustiness refers to the rate of change of wind speed, usually identified with the turbulent intensity defined by ratio of the standard deviation of the mean wind speed to the mean itself. The important wind gusts are those lasting 2–3 seconds, being the time taken to perform a simple act such as a few walking steps, opening a door etc.

Gustiness is a difficult factor to assess on the urban micro-scale. Fortunately, the implied turbulent intensity may be related to the underlying means in order to recast gustiness criteria in terms of mean wind speed (Twidell, 2006), (Melbourne, 1978), (ASHRAE, 2001), (Blocken, 2004). Estimates of turbulent intensity in urban situations range from 15% to 30% (Twidell, 2006), implying that gust wind speeds are generally 1.5–2.0 times greater than mean wind speeds.

2.2 Comfort In general, comfort criteria relate to both the thermal effects of wind on people, and the mechanical effects of wind on their activities.

The comfort criteria used in this study (Hunt, 1976) are a modification of the Lawson criteria, based on the probability of exceeding certain mean wind speeds with the implied gustiness taken into account. The criteria are presented in Table 1. Wind conditions are unacceptable when the probability of the mean wind speed exceeding the given number is greater than 5%. Table 1: The wind comfort criteria used in this study.

Activity Type Examples Limiting Mean Wind Speed (m/s)

Long-term sedentary Outdoor dining, picnicking, outdoor games 3.5 Short-term sedentary Queuing, talking in groups 5.5 Slow movement Window shopping 7.5 Rapid movement Walking through, skateboarding, cycling 10.0



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3.0 The local wind climate

3.1 Meteorological data The wind data was taken from the Bureau of Meteorology automatic weather station at RAAF Base Williamtown1.

The wind speed data was rescaled to account for the difference in land surface structure between the meteorological station and the development site, and the height difference between the anemometer and the level at which people are affected (assumed to be 2 metres). The rescaling was accomplished using a power-law approximation to a neutrally stable atmospheric boundary layer profile (Pasquill-Gifford Class D) (Melbourne, 1978), (Simiu, 1986) and the parameters shown in Table 2 using the equation:

=

In which is the wind speed referred to the NeW Space site and the reference height of people therein, and is the wind speed measured at RAAF Base Williamtown. The other symbols have the meanings shown in

Table 2.

Wind speeds below 0.5 m/s are registered by the anemometer as zero (calm).

Table 2: Parameters used to rescale the raw meteorological data to account for site characteristics.

Parameter Symbol Units Value Atmospheric boundary layer thickness at meteorological station met m 270 Atmospheric boundary layer thickness at development site site m 370 Anemometer height Hmet m 10.0 Reference height H0 m 2.0 Power-law exponent at meteorological station amet – 0.14 Power-law exponent at development site asite – 0.22

3.2 Summary statistics The wind data was analysed to assess the likelihood of uncomfortable winds, without allowing for the presence of the development. Local wind effects due to the development will be discussed in the next section.

The analysis was carried out using:

- The entire data set, representing wind conditions throughout the 24-hour day

- A subset restricted to the hours of 0700 to 1900 (working hours) when commercial and shopping areas would be most active

- A subset restricted to working hours during winter (June-August), the season when high winds are most likely to cause discomfort.

The final two cases are most relevant to the predicted uses of the outdoor spaces.

Wind speed

Calm conditions occur rarely during business hours at around 7% of the time, which increases to 10% during winter. Wind speeds at pedestrian height are generally low compared to the comfort criteria (Figure 1 on the following page). The frequency with which each criterion is exceeded is shown in Table 3. Only the criterion for long-term sedentary activities is exceeded with significant frequency.

1 Station number 061078. The data consisted of hourly wind speed and direction, maximum gust speed, temperature and other variables from 1/1/1989 to 28/10/2011. After quality checks, there were a total of 167,643 suitable records.



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Figure 1: Distribution of wind speeds during winter business hours

Table 3: The probability of the wind speed comfort criterion being exceeded for each activity type. Probabilities less than 5% are

considered acceptable.

Frequency of higher wind speed

Activity Type All hours & seasons



Long-term sedentary (>3.5 m/s) 17.2% 25.3% 24.9% Short-term sedentary (>5.5 m/s) 2.0% 3.1% 4.9% Slow movement (>7.5 m/s) 0.2% 0.4% 0.6% Rapid movement (>10.0 m/s) 0.0% 0.1% 0.0%

Wind direction

While the distribution of wind direction is variable over all hours and seasons, north westerlies are by far the predominant wind heading, especially during winter. In the warmer months, winds tend to blow from the north east through to south, and it is these wind directions that will be considered in the impact analysis.

Figure 2: Distribution of wind heading for all times and seasons (left) and business hours only (right)

0%

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Calm 1 2 3 4 5 6 7 8 9 10

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Occurrence Frequency Cumulative Frequency

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320330

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4.0 Comfort assessment

4.1 Wind-sensitive locations The analysis in section 3.0 indicates that only long-term sedentary activities may be vulnerable to wind discomfort. The presence of the development may accelerate winds in certain areas, which may also increase the probability of discomfort during short-term sedentary activities.

The sensitive areas around the NeW Space building are:

The seating area on the corner of Auckland Street and Hunter Street;

The courtyard between NeW Space and the Civic Theatre; and

The Urban Rooms located throughout the building.

Due to the narrowing gap between NeW Space and University House, there is a risk that prevailing north-westerly winds may accelerate to uncomfortable speeds.

4.2 Corner of Auckland Street and Hunter Street The seating area is located under a building setback, however is exposed to any winds that blow along Auckland or Hunter Streets. It is unlikely that there will be significant acceleration of winds along these streets due to the relatively low height buildings lining the street. As the building is set back from the corner of the intersection, winds are likely to flow relatively freely around the corner. It is likely that this area will be suitable for short-term sedentary activities for the majority of the time.

Figure 3: Seating area on the corner of Auckland and Hunter Streets

4.3 Courtyard The courtyard space is exposed to southerly winds which may blow across Civic Park and Christie Place, however conditions here are unlikely to be any less comfortable than those currently experience in these two open areas. Winds from the south are generally faster than the average from all directions, and the proposed use of trees throughout the space is likely to assist in creating comfortable conditions in the seating areas.



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Figure 4: Courtyard and proposed landscaping

4.4 Urban rooms The urban rooms are located on all facades of the building, and due to their height off the ground, are completely exposed to oncoming winds. These spaces have full height balustrades, extending to 2100mm above floor level, which will provide a significant protection to occupants using the space. There is unlikely to be a significant risk of downwash impacting the urban rooms due to the overhang that surrounds, and therefore protects the space. It is therefore unlikely that there will be any detrimental wind impacts in the urban rooms.

Figure 5: Urban rooms throughout NeW Space



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5.0 Conclusion

5.1 Likelihood of discomfort Table 4 shows the overall likelihood of exceeding the various discomfort criteria in different areas around the development. In the north-eastern urban park winds are likely to be sometimes uncomfortable for the intended use of the space. Discomfort is most likely to be felt during winter business hours, but the likelihood remains significant at other times of year.

Other areas may occasionally be uncomfortable for long-term or short-term activities, but no more frequently than expected of any typical development in this location.

Table 4: Assessed likelihood of exceeding comfort criteria in various areas, ranked as COMMON (10% or greater), OCCASIONAL (5%-

10%), RARE (1%-5%) or VERY RARE(less than 1%).

Risk level

Area Activity Type All hours & seasons



Corner of Auckland and Hunter Streets

Long-term sedentary RARE OCCASIONAL OCCASIONAL Short-term sedentary RARE RARE RARE Slow movement VERY RARE VERY RARE VERY RARE Rapid movement VERY RARE VERY RARE VERY RARE

Courtyard Long-term sedentary OCCASIONAL OCCASIONAL OCCASIONAL Short-term sedentary RARE RARE RARE Slow movement VERY RARE VERY RARE VERY RARE Rapid movement VERY RARE VERY RARE VERY RARE Urban Rooms Long-term sedentary RARE RARE RARE Short-term sedentary VERY RARE VERY RARE VERY RARE Slow movement VERY RARE VERY RARE VERY RARE Rapid movement VERY RARE VERY RARE VERY RARE Walkway between NeW Space and University House

Long-term sedentary COMMON COMMON COMMON Short-term sedentary OCCASIONAL COMMON COMMON Slow movement OCCASIONAL OCCASIONAL OCCASIONAL Rapid movement RARE RARE RARE

5.2 Mitigation It is likely that with the inclusion of the proposed landscape design (shown in Appendix A), the areas used by pedestrians and occupants are comfortable for their intended use. As such, no further mitigation is recommended.



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References [1] Twidell, J. and Weir, T. (2006), Renewable Energy Resources, 2nd edition, Taylor and Francis pubs.

[2] Melbourne, W.H. (1978), Criteria for environmental wind conditions, Journal of Industrial Aerodynamics 3, 241–249.

[3] Simiu, E. and Scanlan, R.H. (1986), Wind effects on structures, 2nd ed., John Wiley & Sons.

[4] ASHRAE Handbook 2001, F16.3

[5] Blocken, B. and Carmeliet, J. (2004), Pedestrian wind environment around buildings: literature review and practical examples, Journal of Thermal Environment and Building Science, 28 (2), 107–159.

[6] Hunt, J.C.R., Poulton, E.C. and Mumford J.C. (1976), The effects of wind on people: new criteria based upon wind tunnel experiments, Buildings and Environment 11, 15–28.

[7] Davenport, A.G. (1972), An approach to human comfort criteria for environmental wind conditions, Colloquium on Building Climatology, Stockholm.

[8] CIBSE (2005), Natural ventilation in non-domestic buildings, CIBSE Applications Manual AM10.

[9] ACTPLA (2011), CZ5 Mixed Use Zone Development Code, ACT Parliamentary Counsel



Appendix A

Proposed Landscape Design



A-1

Appendix A Proposed Landscape Design

wind microclimate assessment

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