DAPPLE - Wind Tunnel Modelling H. Cheng and A. Robins University of Surrey Low resolution model...
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Transcript of DAPPLE - Wind Tunnel Modelling H. Cheng and A. Robins University of Surrey Low resolution model...
DAPPLE - Wind Tunnel ModellingH. Cheng and A. Robins
University of Surrey
Low resolution model (1:200)Experimental set-upQuality assurance for experimentsMean concentration measurementsPuff releasesConclusions and future work
Low resolution model
• Model scale: 1:200• Flat roof• Height refers to the building eaves• Street block is modelled as rectangular block• Model mean height: 22m (110mm)• Model co-ordinates
Experimental set-up
• Tunnel test section: 4000x700x300m (20x3.5x1.5 m)• Neutral BL without considering traffic simulation• Model mounted on turntable• Uref=2.5 m/s, south-westerly wind (45˚)• Instrumentation: FID and FFID• Source located in York St. • ID=1.2m(6mm) for mean concentration• ID=2.3m (11.5mm) for instantaneous concentration• Ground level concentration
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)
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
Data from one experiment
Data from two experiments
Data from all experiments
Range from about 50 to 500m
Short-duration releases
• 10s duration pulses (travel, rise and decay time scales)
• Variable puff duration (0.5 to 4s)
Characteristic time scales
Measured time scales
Puff - single realisation and ensemble average
Conclusions
Plumes: C*max 1/R2
Significant variations across streetsPuffs: 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
Detail near intersection