Gully performance – connecting above and below ground system

EPSRC Grant: EP/FP202511/1

Ida SabtuGavin Sailor

John BlanksbyAdrian Saul

Istvan GalambosGavin TaborAlbert Chen

Slobodan Djordjević

Interaction of flows above & below ground inflow

Q=?Q=?

overflow (geysering)

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

Methodology • Experimental investigation• Numerical simulation (CFD)• Identification of parameters

urban surface + inlet grating + gully structure underneath

(+ surcharged pipe + header tank)

Full-scale experimental setup

Experiments

flow into the gully overflow from the gully

Experimental conditions • Flow directions:

– into the gully– overflow from the gully– transition

• Range of flow rates• Varying surface slope

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

OpenFOAM model computational grid

fine 3D mesh nested 2D/3D model

Effect of cross slope on flow patterns=1:20 s=1:60 s=1:200

D istribution of flow into gullyC ross slope 1 :20

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

Pe

rcen

tag

e o

f flow

[%]

S ection1 S ection2 S ection3

D istribution of flow into gullyC ross slope 1 :60

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

Pe

rcen

tag

e o

f flow

[%]

S ection1 S ection2 S ection3

D istribution of flow into gullyC ross slope 1 :200

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

Pe

rcenta

ge of flow

[%]

S ection1 S ection2 S ection3

Comparison of simulated and observed depths

Median 25%-75% Non-Outlier Range Outliers ExtremesF60-D1

F60-D2F60-D3

F60-D4F60-D5

F60-D6

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Dep

th [

cm]

SimulatedMeasured:

6 measurement points

Gully overflow/surface flow interaction

Links to related projects

• University of Coimbra (experimental & CFD modelling)• EU SKINT project (field testing of gullies in Bradford)

Concluding remarks• Dual drainage modelling has become a common practice• Interaction of flows above and below ground can now be

modelled more reliably