Particles in unbounded flows

The interaction between a fluid medium and suspended solid particles is a highly intriguing dynamical process which is at play in many natural and technical systems. Predicting the particle motion and its feed-back upon the fluid flow has been a challenge for engineers and scientists alike for a long time. Particulate flow phenomena include the emergence of heterogeneous spatial distributions of the disperse phase, with important practical consequences: how fast does a particle collective settle uner gravity? How does turbulence affect the inter-particle collision frequency? How does the presence of particles impact the turbulence characteristics?

Modern experimental techniques and high-fidelity numerical simulations are able to provide data at unprecedented resolution. Based upon this information we are attempting to unravel some of the long-standing open questions in the field. Below you can find a short list of related publications from our work.

[1] A. Chouippe and M. Uhlmann. On the influence of forced homogeneous-isotropic turbulence on the settling and clustering of finite-size particles. Acta Mechanica, 230:387--412, 2019 [DOI] 

[2] M. Uhlmann and A. Chouippe. Clustering and preferential concentration of finite-size particles in forced homogeneous-isotropic turbulence. J. Fluid Mech., 812:991--1023, 2017 [DOI]
 

DNS of fluid-particle systems 

The intercation between turbulent flows and solid particles is a question of technological relevance, with a wide range of applications in hydraulics, meteorology, process engineering, energy technologies, bio-medical flows etc. We study fluid-particle systems by means of direct numerical simulation with fully resolved phase boundaries. The aim is to analyze processes such as the formation of particle agglomerations and the enhancement /attenuation of turbulence intensity. In the long run, our object is to contribute to an improvement of commonly used engineering models for multiphase flow.
 

Dynamics of coherent structures

An understanding of fundamental dynamic processes in turbulent flows is essential in determining scaling laws and can be understood as a prerequesite for technological applications. As an example, detailed knowledge of the regeneration mechanism of turbulent near-wall structures can inspire strategies for boundary layer control.

One of the phenomena studied in our group is the generation of secondary flow in a square duct due to coherent structures. Another topic of interest is the analysis of turbulent flows with stratification, which are of great importance to geo-physical applications (e.g. ocean currents). For stable stratification there is a competition between damping buoyant forces and the intrinsic instability of the shear flow.
 

LES of complex flows

Large Eddy Simulation (LES) is very suitable for the calculation of turbulent flows in cases where no direct simulation is possible because of geometrical complexity and/or high Reynolds numbers. This applies in particular to cases with unsteady flow separation where purely statistical models typically do not provide accurate predictions.