1. Gully performance – connecting above and below ground system EPSRC Grant: EP/FP202511/1 Ida Sabtu Gavin Sailor John Blanksby Adrian Saul Istvan Galambos Gavin Tabor Albert Chen Slobodan Djordjević

2. Interaction of flows above & below ground inflow Q=? overflow (geysering)

3. Research objectives Improved understanding of interactions Reliable head/discharge relationships Enhancement of urban flood models Better flood risk management

4. Methodology Experimental investigation Numerical simulation (CFD) Identification of parameters

5. urban surface + inlet grating + gully structure underneath (+ surcharged pipe + header tank) Full-scale experimental setup

6. Experiments flow into the gully overflow from the gully

7. Experimental conditions Flow directions: – into the gully – overflow from the gully – transition Range of flow rates Varying surface slope

8. Measurements Flow rates (inflow, outflow) Surface water levels (54 points) Pressure in the gully and at 6 surface points

9. OpenFOAM model computational grid fine 3D mesh nested 2D/3D model

10. Effect of cross slope on flow pattern s=1:20 s=1:60 s=1:200

11. Comparison of simulated and observed depths Median 25%-75% Non-Outlier Range Outliers Extremes F60-D1 F60-D2 F60-D3 F60-D4 F60-D5 F60-D6 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Depth [cm] Simulated Measured: 6 measurement points

12. Gully overflow/surface flow interaction

13. Links to related projects University of Coimbra (experimental & CFD modelling) EU SKINT project (field testing of gullies in Bradford)

14. Concluding remarks Dual drainage modelling has become a common practice Interaction of flows above and below ground can now be modelled more reliably