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Sediment movement model development

IMPACT. Investigation of extreme flood Processes and uncertainty. Sediment movement model development. Yves Zech, Sandra Soares Frazão Benoit Spinewine, Nicolas le Grelle Université catholique de Louvain, Belgium IMPACT fourth workshop Zaragoza - November 2004. IMPACT ‘sediment’ team.

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Sediment movement model development

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  1. IMPACT Investigation of extreme flood Processes and uncertainty Sediment movement model development Yves Zech, Sandra Soares Frazão Benoit Spinewine, Nicolas le Grelle Université catholique de Louvain, Belgium IMPACT fourth workshop Zaragoza - November 2004

  2. IMPACT ‘sediment’ team • UCL Louvain, Belgium • UDT Trento, Italy • IST Lisbon, Portugal • Cemagref Lyons, France Sediment movement in dam break

  3. Aims and objectives Improve the prediction of the motion of sediments in association with catastrophic floods Sediment movement in dam break

  4. Solid transport and extreme flows Sediment movement in dam break

  5. Types of catastrophes • Dam break • Debris flows and mud flows • Floating debris and clogging • Glacial lake outburst flood (GLOF) • Landslides • Bank failure into the dam reservoir • Obstruction by natural dams Sediment movement in dam break

  6. Issues of sediment movement • Extreme flows  intense erosion and solid transport • Intense sediment transport  affects flood-wave prediction • Arrival time • Maximum water level • Morphological changes Sediment movement in dam break

  7. Scope of the research • Near-field • Uniform debris flow • Severe transient debris flow • Far-field • Intense transport • Bank erosion and geomorphic changes Sediment movement in dam break

  8. Scope of the research • Near-field • Uniform debris flow • Severe transient debris flow • Far-field • Intense transport • Bank erosion and geomorphic changes Sediment movement in dam break

  9. Dam-break near field • t = 0.0 s • t = 0.2 s • t = 0.4 s Sediment movement in dam break

  10. Dam-break near field • Physical description Sediment movement in dam break

  11. Near field : problems to be solved • Initiation of movement • Acting forces • Vertical effects • Inertial effects • Sediments bulking • Propagation • Intense scouring • Debris-flow front Sediment movement in dam break

  12. Near-field : IMPACT research program • Debris flow : acting forces (Trento) • Dam-break experiments (Louvain) • Dam-break numerical modelling (Louvain) • Validation of codes (Trento, Louvain, Cemagref) Sediment movement in dam break

  13. Debris flow • Experiments • Trento tilting flume (L = 6 m, S0 = 0° to 23°) • Types of particles • Uniform cylindrical PVC particles • Graded material Sediment movement in dam break

  14. Debris flow • Mature debris flow : collisional + frictional Sediment movement in dam break

  15. Debris flow • Mature debris flow Sediment movement in dam break

  16. Debris flow immature mature plug rigid bed Sediment movement in dam break

  17. Debris flow • Particle segregation • Small particles have a higher probability to find a hole into which to fall x = 9 cm Sediment movement in dam break

  18. Debris flow • Particle segregation • Small particles have a higher probability to find a hole into which to fall x = 33 cm Sediment movement in dam break

  19. Debris flow • Particle segregation • Small particles have a higher probability to find a hole into which to fall x = 63 cm Sediment movement in dam break

  20. Debris flow • Particle segregation • Small particles have a higher probability to find a hole into which to fall x = 90 cm Sediment movement in dam break

  21. Radial distribution = rate of collisions Debris flow • Mathematical description (collisional) • Normal stress local equilibrium • Kinetic theory of dense molecular gas • Inter-granular quasi-elastic approximation (pressure related to granular temperature Ts) Sediment movement in dam break

  22. Debris flow • Mathematical description (collisional) • Tangential stress local equilibrium Sediment movement in dam break

  23. Debris flow • Mathematical description (collisional) • Tangential stress local equilibrium • Effect of added mass Sediment movement in dam break

  24. Debris flow • Added mass effect Sediment movement in dam break

  25. Dam-break near-field experiments • Flat bed case • PVC • Louvain old flume • Gates moving up h0 hs Sediment movement in dam break

  26. Dam-break near-field experiments • Stepped-bed case • Materials • PVC • Sand • Louvain new flume • Gates moving down Sediment movement in dam break

  27. Stepped-bed case Sediment movement in dam break

  28. t Visual observation x xb(t) xf(t) Velocity gradient Dam-break near-field experiments • Interfaces Sediment movement in dam break

  29. Flat- and stepped- bed benchmarks • Four participants • Cemagref Lyons, France • UDT Trento, Italy • IST Lisbon, Portugal • UCL Louvain, Belgium Sediment movement in dam break

  30. NS vorticity equation • Stream functions Numerical model : 2D-V description • Level set model (Louvain) Sediment movement in dam break

  31. Numerical model : 2D-V description • Level set model Sediment movement in dam break

  32. Numerical model : 1D description 1 • St-Venant - Exner (Cemagref) • Only water layer Sediment movement in dam break

  33. Numerical model : 1D description 1 Sediment movement in dam break

  34. Numerical model : 1D description 1 • Closure • Solid discharge Qs • Friction slope Sf Sediment movement in dam break

  35. Numerical model : 1D description 2 • Two-layer model (Trento) • Same velocities • Same concentrations Sediment movement in dam break

  36. Numerical model : 1D description 2 Sediment movement in dam break

  37. Numerical model : 1D description 2 • Closure : • Erosion • Shear stresses • Shear stress tb= f (c, f) Sediment movement in dam break

  38. Numerical model : 1D description 3 • Two-layer model (Lisbon) • Averaged velocity • Distinct concentrations Sediment movement in dam break

  39. Numerical model : 1D description 3 Sediment movement in dam break

  40. Numerical model : 1D description 3 • Closure • sheet-flow data (Sumer) • shear stress • power-law distribution • transport Fs from where Sediment movement in dam break

  41. z pure water mixture u Numerical model : 1D description 4 • Two-layer model (Louvain) • Distinct velocities • Distinct concentrations Sediment movement in dam break

  42. Numerical model : 1D description 4 Sediment movement in dam break

  43. Numerical model : 1D description 4 • Closure : • Erosion • Shear stresses and • Shear stress tb= f (c, f) Sediment movement in dam break

  44. h0 Validation : flat-bed benchmark • Front and back waves Sediment movement in dam break

  45. h0 Validation : flat-bed benchmark • Evolution at section x = 5 h0 Sediment movement in dam break

  46. Validation : flat-bed benchmark • One-layer model • water surface OK • no sediment layer Sediment movement in dam break

  47. Validation : flat-bed benchmark • One-velocity model • front celerity calibrated • sediment layer underestimated Sediment movement in dam break

  48. Validation : flat-bed benchmark • Two concentrations • best water level • sediment layer overestimated; no erosion Sediment movement in dam break

  49. Validation : flat-bed benchmark • Two-layers • water front in advance • best sediment layer; erosion and deposition Sediment movement in dam break

  50. Validation : flat-bed benchmark Sediment movement in dam break

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