Defoaming Additives in Horizontal Multiphase Flow—Impact on Flow Regime and Separations
Recorded on September 16, 2013 (90 minutes)

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The Effect of Surfactant on Stratified and Stratifying Gas-Liquid Flows

The inlet conditions of the fluids entering a separation vessel have a significant impact on the performance of the separator. The STTS Webinar on Inlet Flow Conditioning and on Foam earlier in 2013 both addressed factors contributing to this impact. In the effect of surfactant on stratified and stratifying gas-liquid flows the impact of chemicals altering the flow map and droplet size distribution are investigated both of which significantly impact separation performance. In the study we consider the dynamics of a stratified/stratifying gas-liquid flow in horizontal tubes. This flow regime is characterized by the thin liquid films that drain under gravity along the pipe interior, forming a pool at the bottom of the tube, and the formation of large-amplitude waves at the gas-liquid interface. This regime is also accompanied by the detachment of droplets from the interface and their entrainment into the gas phase. This project, one of the first of its kind, will involve carrying out an experimental study involving axial- and radial-view photography of the flow, in the presence and absence of surfactant. One of the aims is to show the effect of surfactant on the average diameter of the entrained droplets, and elucidating the mechanisms underlying these effects. The other aims are to highlight the influence of surfactant on the characteristics of the interfacial waves, and the pressure gradient that drives the flow. 


Professor Omar K. Matar

Prof. O. K. Matar (OKM) is an Exxon-Mobil Fellow and Professor of Fluid Mechanics in the Department of Chemical Engineering, Imperial College London. OKM’s current research interests are in the area of multiphase flows with applications in oil-and-gas flow-assurance, crude-oil processing, enhanced oil recovery, process intensification, coating flow technology, and manufacturing. OKM has recently been invited to review the field of thin films in Rev. Mod. Phys. (impact factor 51).

OKM is the current coordinator of the Fluid Mechanics Focus Area at Imperial and has received £11M funding (£8M as Principal Investigator) from the Engineering and Physical Sciences Research Council, UK. OKM is the director of the Transient Multiphase Flow consortium (, which comprises a number of oil-and-gas operators (inc. BP, Chevron, Petrobras, Statoil, TOTAL), design- and software-houses. The research council and industrial funding has been used to study phase inversion in concentrated emulsions, flows over rapidly rotating discs (reactors), nonlinear bubble sound interactions, fouling in heat exchangers in crude oil distillation units, dynamics of liquids spreading on compliant substrates, multiphase flow in large-diameter pipes, advanced experimental and numerical methods for the prediction of complex vapour liquid annular flows, and interfacial behaviour in stratified and stratifying annular flows. OKM is also the director of the EPSRC Programme Grant (£5M), MEMPHIS (, to produce the next-generation predictive tools for multiphase flows.

OKM has co-authored 130 articles in prestigious journals and has an h-index of 26. He is the Editor-in-Chief of Multiphase Science and Technology, an Associate Executive Editor of Journal of Engineering Mathematics, and on the Editorial Board of International Journal of Multiphase Flow.