Our EWC seminar on this Friday, Apr 20, will feature Dr. Celso Castro-Bolinaga from the NCSU Department of Biological & Agricultural Engineering. He will discuss: “Dynamics of Fine-Grained Sediment Pulses in River Corridors: An Adaptive Numerical Simulation Approach.” An abstract and bio are included below. Please join us in Mann 304 from 12:50-1:40pm.

Abstract: An adaptive numerical simulation approach to characterize the propagation of fine-grained sediment pulses in river corridors will be presented. The objective of this work was to identify the properties of these types of pulses and those of riverine environments that are more relevant to their downstream migration. Numerical tests were carried out to investigate the influence of the pulse grain size distribution and volume, as well as the influence of the ambient discharge and channel slope, on the dominant propagation mechanisms. Results indicate that the reconfiguration of the deposited material is governed by an initial dispersion-dominated phase during which there is a rapid movement of the pulse forefront, followed by a subsequent phase characterized by a pronounced translational movement of the pulse apex. The dispersion phase is governed by suspended-load driven regimes that actively entrain material from the top part of the pulse, carrying finer sediment further downstream while depositing coarser particles close to the original forefront location. During the translational phase, on the other hand, the velocity in the flow field surrounding the pulse topography decreases and the sediment transport regime is no longer controlled by suspended load, but rather by a combination of this mode of transport near the pulse forefront and bedload transport across the pulse core region. The transition between these two phases is controlled by the value of the Froude number (Fr) over the pulse topography, whereas their intensity and duration are dictated by the magnitude of the evaluated properties. Results suggest that the initial dispersive phase is characterized by high values of Fr (i.e., Fr ~ 0.7-0.9), whereas the translation component detected during the second phase is typically associated with more moderate values of Fr (i.e., Fr < 0.5). The numerical simulations indicated that, independently of the parameter being tested, the degree of translation is enhanced as the magnitude of Fr decreases, and the transition between dispersion and translation occurs around a threshold value of Fr ~ 0.4-0.5. Moreover, the influence of the evaluated parameters was observed to be relevant to the intensity and duration of each phase.

Bio: Dr. Celso Castro-Bolinaga is an Assistant Professor in the Department of Biological and Agricultural Engineering at NC State University, where he leads the Fluvial Hydraulics and Sediment Dynamics Research Group. He received his Ph.D. and M.S. in Civil Engineering from Virginia Tech, and completed his undergraduate studies in Civil Engineering at Universidad Católica Andrés Bello (UCAB) in Caracas, Venezuela. Dr. Castro-Bolinaga’s research group focuses on studying processes that are governed by the dynamics of water and sediment in riverine environments. He and his team aim to provide a better understanding of how the spatial and temporal scales associated with such processes control hydro-geoenvironmental regimes in streams and rivers, and ultimately the adaptation capacity of these natural systems to external drivers (e.g., climate and hydraulic works).