ucl-november 03sediment movement - ucl1 impact - wp4 sediment movement work overview université...

UCL-November 03 Sediment movement - UCL 1

IMPACT - WP4IMPACT - WP4

Sediment movementSediment movementWork overviewWork overview

Université catholique de Louvain

Nicolas le Grelle, Benoit Spinewine and Yves Zech


Scope of the researchScope of the research

• Near-field – Severe transient debris flow

• Far-field – Bank erosion and geomorphic changes


Near field : problems to be solvedNear field : problems to be solved

Propagation– Intense scouring– Debris-flow front


Dam-break near fieldDam-break near field

• Experiments : uniform material (UCL)– Rising gate– Same bed levels

– Sediments swept along the rising gate– Limited water depth



• Construction of a new flume– Downwards

moving gate– Various

bed levels– Possibility of

enlargement


• Mathematical modelling– 1D model :

• Velocity distribution• Concentration distribution


pure water

mixture

u

z



• Validation of codes – Benchmark BM UCL 1 :

1D dam-break flow in the near field

L = 0.10 m

h0 0.10 m

hs


Far field : problems to be solvedFar field : problems to be solved

• Geomorphic changes– Bank erosion and failure

• Tractive forces applied• Failure mechanism

– Channel widening

Brooks & Lawrence, 1999Brooks & Lawrence, 1999


Far field : programmeFar field : programme

• Laboratory experiments– Dam-break in an initially prismatic valley– Large-scale model (Châtelet)

• Numerical modelling

• Validation (UCL, UDT, Cemagref, IST)– Laboratory tests– Field cases


Dam-break far-fieldDam-break far-field

• Laboratory experiment– Dam-break in an initially prismatic valley



• Laboratory experiment– Dam-break in an initially prismatic valley

Gate

erodible channel

rigid bank

Gate

erodible channel

(a) (b )



Dam-break in

an initially

prismatic valley

1

2

3



• Dam-break in an initially prismatic valley– Images treatment



• Dam-break in an initially prismatic valley– Reproducibility

t = 1 s



• Dam-break in an initially prismatic valley– Reproducibility

t = 5 s



• Dam-break in an initially prismatic valley– Initial conditions (benchmark)

Upstream Downstream

50°

8 cm

16 cm

30 cm

57 cm



• Large scale model

at LRH-Châtelet



• Large scale model

at LRH-Châtelet

3,90 m

1,535 m

Weight = 190 kg

Jack = 2400 N

Opening time = 1 sec



• Large scale model : Test 1 - Calibration

h s

h0

Gate1 m



• Large scale model : Test 2 - Benchmark

h0

hs



• Large scale model : Test 3 - Benchmark

Section BBSection AA

AA BB

h0

hs

1 m 3 m


Dam-break far fieldDam-break far field

• Sand behaviour for small-scale laboratory exp.– Humid sand– Residual water– Apparent cohesion– Disappears when underwater

• « Rotating tank » experiments– Different angles of repose

• Emerged• Submerged



• Modelling of bank failures– Simple model accounting for discrete mass failure

events• Distinct angles of repose for submerged and emerged

banks• Failure triggered whenever and wherever critical angles

exceeded• To be extended to 2D by invoking conic failure surfaces

8 5 °

3 7 °

5 0 °

q s

c e

c s h

i



• 1D Numerical modelling– Hydrodynamic: finite volume, Roe– Sediment transport: non-equilibrium,

bed and submerged banks– Bank failure

• Two angles of failure(emerged & submerged)

• Two angles of repose(emerged & submerged)

qs

gliss,hum

gliss,eau

qd = qs dep,hum

dep,eau


ComparisonComparison

• 1D Numerical modelling



• Field test : Lake Ha!Ha!

Brooks & Lawrence, 1999Brooks & Lawrence, 1999


IMPACT - WP4IMPACT - WP4

Sediment movementSediment movementWork overviewWork overview

Université catholique de Louvain

Nicolas le Grelle, Benoit Spinewine and Yves Zech

ucl-november 03sediment movement - ucl1 impact - wp4 sediment movement work overview université...

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