Sun, Aug 11, 2019 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Speaker: Eckart Meiburg, UC Santa Barbara
Talk Title: Settling of Cohesive Sediment: Particle resolved Simulations
Abstract: We develop a physical and computational model for performing fully coupled, grain resolving Direct Numerical Simulations of cohesive sediment, based on the Immersed Boundary Method. The model distributes the cohesive forces over a thin shell surrounding each particle, thereby allowing for the spatial and temporal resolution of the cohesive forces during particle to particle interactions.
We test and validate the cohesive force model for binary particle interactions in the Drafting-Kissing-Tumbling aka DKT configuration. Cohesive sediment grains can remain attached to each other during the tumbling phase following the initial collision, thereby giving rise to the formation of flocs. The DKT simulations demonstrate that cohesive particle pairs settle in a preferred orientation, with particles of very different sizes preferentially aligning themselves in the vertical direction, so that the smaller particle is drafted in the wake of the larger one. This preferred orientation of cohesive particle pairs is found to remain influential for much larger simulations of 1,261 polydisperse particles released from rest. These simulations reproduce several earlier experimental observations by other authors, such as the accelerated settling of sand and silt particles due to particle bonding, the stratification of cohesive sediment deposits, and the consolidation process of the deposit. This final phase also shows the build-up of cohesive and direct contact intergranular stresses. The simulations demonstrate that cohesive forces accelerate the overall settling process primarily because smaller grains attach to larger ones and settle in their wakes. An investigation of the energy budget shows that the work of the collision forces substantially modifies the relevant energy conversion processes.
Biography: Eckart Meiburg received his Ph.D. from the University of Karlsruhe. After a postdoc at Stanford, he became an assistant professor in applied mathematics at Brown. He then moved to USC as associate then full professor. He later moved to UC Santa Barbara.
His research interests are fluid dynamics and transport phenomena, primarily computational fluid dynamics. He uses highly resolved direct numerical simulations to investigate physical mechanisms governing the spatio temporal evolution of a wide variety of geophysical, porous media, and multiphase flow fields. Some of his current interests are gravity and turbidity currents, Hele-Shaw displacements, double diffusive phenomena in particle laden flows, and internal bores.
Meiburg has received a Presidential Young Investigator Award, a Humboldt Senior Research Award, and a Senior Gledden Fellowship Institute of Advanced Studies, University of Western Australia. He is fellow of the American Physical Society and the ASME, was the 2012 Lorenz G. Straub Award Keynote Speaker at Univ. Minn., gave the Ronald F. Probstein Lecture at MIT in 2018, and was Shimizu Visiting Professor at Stanford University.
Location: SLH 102
Audiences: Everyone Is Invited
Contact: Tessa Yao