Hydraulics & Waterways


398052 - A simple, single-size and time-dependent flocculation model

Wednesday, June 6
4:00 PM - 5:30 PM
Location: Greenway CD
Co-Authors: Rachel Kuprenas, Blacksburg, VA – Virginia Tech; Duc Tran, Blacksburg, VA – Virginia Tech

Scientists and engineers rely on physics-based models to evaluate the transport and deposition of sediment in water systems. The accuracy of such models depends heavily on the selection of an appropriate sediment settling velocity. For non-cohesive sediment, the settling velocity is relatively easy to calculate as the size, density, and shape of the particles do not change; however, for cohesive particles, which can form flocs, the settling speed is more complex to estimate. The reason for the added complexity is that cohesive particles can create aggregates, called flocs, which can grow or shrink in size as a function of hydrodynamic and physiochemical conditions of the suspension. In this presentation, we present a new and simple model for predicting floc sizes in a dynamic way as a function of the hydrodynamic conditions and inherited floc sizes. The model is simply a modification to the existing Winterwerp (1998) floc size model. However, the modification is significant in that it yields predictions that are more in line with observations over a broad range of conditions. Specifically, the model does not allow predicted floc sizes to surpass the Kolmogorov micro length scale. We present the motivation for the modification, the functionality of the modification, and a comparison of the updated model with laboratory data. Overall the model shows promise as a tool that could be incorporated into larger hydrodynamic and sediment transport models for improved prediction of cohesive mud transport.

Kyle Strom

Associate Professor
Virginia Tech University


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398052 - A simple, single-size and time-dependent flocculation model

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