000199523 001__ 199523
000199523 005__ 20190316235923.0
000199523 037__ $$aPOST_TALK
000199523 245__ $$aA model for entrainment in avalanches and debris flows based on PIV measurements of viscous gravity currents.
000199523 269__ $$a2014
000199523 260__ $$c2014
000199523 336__ $$aPosters
000199523 500__ $$aVol. 16, EGU2014-2604, 2014
000199523 520__ $$aA simple experiment, designed to investigate entrainment in geophysical free-surface flows such as avalanches and debris flows, was performed using a dam break of viscous fluid which travels over a rigid bed until meeting a shallow layer of the same fluid at rest; this represents an avalanche which begins entraining material along its path. Particle image velocimetry (PIV) on a streamwise section in the entrainment zone allowed the measurement of internal flow velocities and the observation of entrainment processes such as bed excavation. Image processing techniques were used to identify surface height and the current/substrate interface. A model was derived for this system, starting from the viscous Navier-Stokes equations for conservation of mass and momentum in domains including entrainable material. The flow is shallow and there is a rigid base, b(x) below z=0, representing the beginning of an entrainable region (modelled by a hyperbolic tangent). The free-surface kinematic boundary condition was used to link surface height and flow velocity, thus removing the need for depth-averaging. The derived equations are solved using a parabolic solver to obtain the surface height and velocity field throughout the flow and the velocities are used in a simple advection scheme, examining the progression of the current/substrate interface at the base of the dam-break. The numerical predictions closely match the experimental observations. Sharp surface height gradients diffuse quickly upon entry into the entrainment zone and the flow front accelerates. The current sinks into the bed and downstream bed material is forced upwards as found in the laboratory. The rates that the current excavates the bed, both in the vertical and streamwise directions, follow the same power laws as observed, and the surface height and internal velocities are in agreement in the model and the experiments.
000199523 6531_ $$aAva
000199523 6531_ $$adebris flows
000199523 6531_ $$aPIV
000199523 6531_ $$aGrav
000199523 700__ $$0246116$$g217820$$aBates, Belinda Margaret
000199523 700__ $$0240366$$g148669$$aAncey, Christophe
000199523 7112_ $$dApril 27 - May 2$$cVienna, AU$$aEGU General Assembly 2014
000199523 720_2 $$aAncey, Christophe$$edir.$$g148669$$0240366
000199523 8564_ $$uhttp://meetingorganizer.copernicus.org/egu2014/sessionprogramme$$zURL
000199523 909C0 $$xU10257$$0252029$$pLHE
000199523 909CO $$qGLOBAL_SET$$pposter$$ooai:infoscience.tind.io:199523$$pENAC
000199523 917Z8 $$x106556
000199523 937__ $$aEPFL-POSTER-199523
000199523 973__ $$aEPFL
000199523 980__ $$aPOSTER