PiCASSO - Particle Collisions for Arbitrary Smooth Shaped Objects - Experimental and numerical investigation: Model development and validation

Research institute: BOKU Institute of Hydraulic Engineering and River Research

Many rivers worldwide suffer from disturbed sediment dynamics due to human and climate impacts. Understanding sediment processes in rivers is a prerequisite for developing efficient sediment management strategies. When dealing with sediment transport processes in rivers most researchers use a standard or modified form of the critical Shields parameter to predict the incipient motion of a grain size of interest. Despite the wide use of this concept, many studies reveal the apparent lack of a precise threshold value. Rather than the temporally and spatially averaged shear stress at the reach scale, instantaneous forces acting on the grain are responsible for its mobilization. Moreover, particle-particle interactions are a main contributor to sediment entrainment and should thus be explored. The interplay of a fluid (e.g. water) with a solid body (e.g. sediment grains) is modeled in the field of fluid-structure-interactions (FSI). If particle-particle collisions need to be considered additional equations have to be solved. The novel 4D-PTV method for high-resolution spatio-temporal measurements of the flow is an excellent way to study FSI problems experimentally. Collision models between spherical objects and spheroidal objects have been developed recently. Despite the fact that the key role of arbitrary shaped objects and polydisperse particles has been acknowledged in recent publications, experimental and numerical studies for high Reynolds number flows and polydisperse arbitrary shaped particles do not yet exist to the best of the authors' knowledge.