1. DAPPLE - Wind Tunnel Modelling H. Cheng and A. Robins University of Surrey Low resolution model (1:200) Experimental set-up Quality assurance for experiments Mean concentration measurements Puff releases Conclusions and future work

2. 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

4. Experimental set-up Tunnel test section: 4000x700x300m (20x3.5x1.5 m) Neutral BL without considering traffic simulation Model mounted on turntable U ref =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

6. 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)

7. Mean concentration measurements Source locations (road side and road centre) Receptors: down wind region Detailed intersection measurements Non-dimensional concentration, C* = CU ref H 2 /Q Upper bound to whole data set: CU ref /Q = 50R -2 not dependent on building height, H

8. Data from one experiment Data from two experiments

9. Data from all experiments Range from about 50 to 500m

10. Short-duration releases 10s duration pulses (travel, rise and decay time scales ) Variable puff duration (0.5 to 4s)

11. Characteristic time scales

12. Measured time scales

13. Puff - single realisation and ensemble average

14. Conclusions Plumes: C*max  1/R 2 Significant variations across streets Puffs: U advection ≈ 0.13 U ref ≈ U H /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

15. Detail near intersection