Numerical Study of Erosion-proof of Loose Sand in an Overtopped Plunging Scour Process– FLOW3D Investigators: Ge Wang, Chung R. Song, Jinwon Kim and Alexander, H.-D. Cheng Civil Engineering Department University of Mississippi
Objectives Failure of floodwalls during Hurricane Katrina, August 23, 2005. Nearly every levee in metro New Orleans was breached. Eventually 80% of the city became flooded . Scouring caused by overtopping flow. This leads to hydrostatic pressure exceeding the designed load that gives rise to failure of Floodwall system. Main goal: investigate levee back side erosion caused by overtopping, and ultimately provide improved technologies for the retrofitting and construction of the nation’s hurricane and flood protection system.
1. FLOW3D for a scour/erosion study • Predict the behavior of packed/suspended sediment with one fluid mode. • 3 dimensional prognostic solver. • Contain a variety of optional turbulent models. • Actual conditions are easily to apply.
(cont.) • Model at a Glance Fluid field drag coeff.
(cont.) Movement of suspended sediment : local lifting, drifting velocity. : local concentration. : diffusion coefficient.
(cont.) • Input parameters for an erosion simulation • Average particle diameter: 0.071 cm • Density of the sediment particles: 2.67 • Critical shields number: 0.00043 • Critical sediment fraction • Cohesive sediment fraction • Sediment drag factor • Angle of repose:
2. Simulation of FLOW3D Four cases:
(cont.) (A) (B) (C) (D)
(cont.) Case B Case A Case D Case C
3. Conclusions • FLOW3D’s sediment scour model is a straightforward approach to modeling erosion and deposition of sediment for fully three-dimensional flows. • Predictions show the scoured domain in agreement with the observations. • Invalid for cohesive material erosion problems.
4.Grant Acknowledgement Department of Homeland Security-through Southeast Region Research Initiative (SERRI), USA. Thanks a lot for your attention! Any questions?