DAPPLE Wind Tunnel Modelling

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DAPPLE - Wind Tunnel Modelling H. Cheng and A.
Robins University of Surrey Low resolution
model (1200) Experimental set-up Quality
assurance for experiments Mean concentration
measurements Puff releases Conclusions and future
work
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• Low resolution model
• Model scale 1200
• Flat roof
• Height refers to the building eaves
• Street block is modelled as rectangular block
• Model mean height 22m (110mm)
• Model co-ordinates

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• Experimental set-up
• Tunnel test section 4000x700x300m (20x3.5x1.5
  m)
• Neutral BL without considering traffic
  simulation
• Model mounted on turntable
• Uref2.5 m/s, south-westerly wind (45)
• Instrumentation FID and FFID
• Source located in York St.
• ID1.2m(6mm) for mean concentration
• ID2.3m (11.5mm) for instantaneous concentration
• Ground level concentration

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• Quality assurance
• Repeatability
• Source flow-rate effects (3-10 l/min)
• Reference wind speed effects
• Frequency response for FFID
• Behaviour of solenoid valve (for short duration
  emissions)

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• Mean concentration measurements
• Source locations (road side and road centre)
• Receptors down wind region
• Detailed intersection measurements
• Non-dimensional concentration, C CUrefH2/Q
• Upper bound to whole data set
• CUref/Q 50R-2

not dependent on building height, H
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Data from one experiment
Data from two experiments
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Data from all experiments
Range from about 50 to 500m
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• Short-duration releases
• 10s duration pulses (travel, rise and decay time
  scales)
• Variable puff duration (0.5 to 4s)

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Characteristic time scales
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Measured time scales
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Puff - single realisation and ensemble average
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• Conclusions
• Plumes Cmax ? 1/R2
• Significant variations across streets
• Puffs Uadvection 0.13 Uref UH/4
• Peak/Mean 3.5 - 4
• Future work
• detailed mapping of flow and concentration
  fields
• flux exchange at intersection
• exchanges with flow above roof level
• effects of modelling detail

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Detail near intersection
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