| Topic: | Wall-bounded turbulence with finite-size particles |
|---|---|
| Speaker: | Prof Luca Brandt KTH Royal Institute of Technology Sweden |
| Date: | Thursday, 9 January 2020 |
| Time: | 10.00am to 11.00am |
| Venue: | Seminar Room EA-06-02   (Block EA, Level 6) (map of NUS can be found at http://map.nus.edu.sg/) |
| Host: | Asst Prof Zhang Mengqi |
Abstract
In the talk we review recent experimental and numerical work at KTH on finite-size particles, i.e. particles larger than the smallest flow structures in wall-bounded turbulence. Experiments have been conducted in duct and pipe flows, measuring pressure drops and turbulence drag over a wide range of particle volume fractions, size and Reynolds numbers. Refractive-index matched Hydrogel particles have also been used to measure fluid and particle velocities.
The data show that the overall drag at high Reynolds numbers is surprisingly similar to that of a single phase flow with an effective viscosity accounting fo the particle presence. This results from two competing effects, particle migration towards the wall and towards the centre of the channel, where large concentration reduce the turbulence activity. Interface resolved simulations, exploiting the Immersed Boundary Method, are used to explain some of the experimental observation. Momentum and energy budget are considered. In addition, a continuum model is proposed to explain the numerical and experimental data at intermediate volume fractions for the smaller particles considered.
Numerical simulations have also examined the behavior non-spherical particles. These data show that particle shape significantly affects the overall suspension dynamics. In particular, oblate particles reduce the turbulent drag by aligning parallel to the wall and shielding the bulk of the flow from the near-wall dynamics.
About the Speaker
Luca Brandt is professor of fluid mechanics at KTH; Royal Institute of Technology, Stockholm, Sweden since 2012. He graduated from University of Rome, La Sapienza, in 1997 and obtained his PhD at KTH in 2003. Since 2018, he is also International Chair, Department of Energy and Process Engineering Faculty of Engineering, NTNU, Norway. In 2014, he was awarded as Outstanding young Researcher, from Swedish Research Council (VR): 9 in all areas of natural and engineering sciences. In 2013 he received a Consolidator Grant from the European Research Council to study particle suspensions. Since 2017 he is director of the multidisciplinary research centre INTERFACE at KTH. He is currently associate editor of Meccanica and European Journal of Mechanics/B fluids. His research focuses on large-scale simulations of transition to turbulence, flow control, non-Newtonian fluids and turbulence flows laden with particles and droplets/bubbles. Prof Brandt was main advisor of 10 graduated PhD students and 11 postdocs; currently he supervises 5 PhD students and 2 postdocs.