Details

Autor(en) / Beteiligte

• Ballio, Francesco
• Pokrajac, Dubravka
• Radice, Alessio
• Hosseini Sadabadi, Seyed Abbas

Titel

Lagrangian and Eulerian Description of Bed Load Transport

Ist Teil von

• Journal of geophysical research. Earth surface, 2018-02, Vol.123 (2), p.384-408

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2018

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Sediment particles transported as bed load undergo alternating periods of motion and rest, particularly at weak flow intensity. Bed load transport can be investigated by either following the motion of individual particles (Lagrangian approach) or observing the phenomenon at prescribed locations (Eulerian approach). In this paper, the Lagrangian and Eulerian descriptions are merged into a unifying framework that includes definitions for quantities used to describe the kinematics of particle motion, as well as the relationships among these quantities. The alternation of motion and rest is represented by two complementary descriptions: (i) proportion of motion, indicating either the relative time spent in motion by an individual particle or the relative number of moving particles; (ii) persistence of motion, indicating the extent to which the process consists of relatively few long periods of motion or of many short ones. The framework only involves first moments of the key quantities. The conceptual developments are tested against results from an experiment with weak bed load transport, demonstrating the soundness of the approach. From an operational point of view, a Lagrangian observation is difficult to perform, since the particle motion is usually investigated for finite spatial domains (e.g., a measurement window within a laboratory or natural reach). Strategies to overcome such limitations are described, suggesting the possibility of obtaining unbiased mean values for Lagrangian descriptors. The proposed framework can be used in any study aimed at parameterizing the kinematic properties of bed load particles as functions of the hydrodynamic conditions. Key Points The Lagrangian and Eulerian approaches to bed load transport are merged into a unifying framework Conceptual derivations involve first moments of key quantities Lagrangian quantities that are difficult to measure can be deduced from Eulerian ones