Pouring a powder onto a liquid interface: dispersion, islands, “lumps” and granular jets

This talk will focus on the wetting and on the dispersion of a powder poured onto a liquid interface, a process conditioning strongly the rehydration and dissolution of dehydrated powders, critical to many industrial sectors (food, pharmaceuticals, detergents, etc.). A stack of grains - a powder island - can be formed upon pouring grains onto a liquid interface and this provides a way to identify the conditions leading to a successful impregnation of the powder pores [1]. A continuous flow of grains onto the interface can induce these islands to grow and sink, forming a partially dry structure that is undesired in application: “a lump” [2]. Pouring grains can also lead to the formation of a jet, entraining air into the liquid. The conditions leading to these different structures will be discussed, presenting also preliminary results on the effect of liquid convection. These results will be linked to previous studies on the wettability of powders [3] and of soluble thin coatings [4].


  1. P.S. Raux et al., Wicking in a powder, (2013) Langmuir, 29 (11), pp. 3636-3644.
  2. X.Y. Ong et al, (2019), submitted.
  3. J. Dupas et al., Powder wettability at a static air-water interface, (2015) Journal of Colloid and Interface Science, 448, pp. 51-56.
  4. J. Dupas et al., Glass transition accelerates the spreading of polar solvents on a soluble polymer, (2014) Physical Review Letters, 112 (18), art. no. 188302.
Dr. Marco Ramaioli obtained a master in chemical engineering summa cum laude from Politecnico di Milano, Italy, with a dissertation on chromatographic reactors under the supervision of Prof. M. Morbidelli. During more than eight years, he gained experience as Process Modelling Specialist and Project Manager at Nestlé PTC Orbe, Switzerland, contributing to the development of several novel food processes and to their factory implementation. In January 2008, he obtained a Science doctorate from Ecole Polytechnique Fédérale de Lausanne with a thesis on granular media flow simulations, under the supervision of Prof. T. M. Liebling. From 2008 to 2014, Dr. Ramaioli held a Project Manager and Senior Research Scientist position at Nestlé Research Center, Switzerland. He contributed to the development of new food products, till their market launch and to advancing the scientific understanding of wetting and dissolution, powder-liquid flows and human swallowing. Since 2013, he lectures at Ecole Polytechnique Fédérale de Lausanne and he contributes to the EdX Massive Online Open Course "Mécanique des fluides". Dr. Ramaioli was appointed Senior Lecturer in Chemical Engineering at the University of Surrey, UK in 2014 and led the research theme Health and Food. Since May 2019 he is Senior Research Scientist at INRA, France and Visiting Reader at University of Surrey.