On the interfacial roughness scale in turbulent stratified two-phase flow: 3D lattice Boltzmann numerical simulations with forced turbulence and surfactant |
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| Institution: | 1. FACE – The Multiphase Flow Assurance and Innovation Center, P.O. Box 40, N-2027 Kjeller, Norway;2. Norwegian Institute for Air Research (NILU), P.O. Box 100, N-2027 Kjeller, Norway;3. Technische Universität München, Arcisstraße 21, 80333 München, Germany;4. Department of Physics, University of Oslo, P.O. Box 1048, Blindern, N-0316 Oslo, Norway;5. Institute for Energy Technology (IFE), P.O. Box 40, N-2027 Kjeller, Norway;6. Department of Chemical Engineering, NTNU, N-7491 Trondheim, Norway;1. School of Science, Tianjin University, Tianjin 300072, China;2. School of Chemical Engineering, Tianjin University, Tianjin 300072, China;1. Department of Environmental Engineering, Faculty of Engineering, Chiang Mai University, Chiang Mai 50200, Thailand;2. Center of Excellence in Materials Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand;1. EQA-CTC/UFSC, Chemical and Food Engineering Department, Federal University of Santa Catarina, C.P. 476, CEP 88040-900 Florianopolis, SC, Brazil;2. SMAP, Surfaces and Porous Materials Group, Faculty of Science, University of Valladolid, P. Belén 7, 47011 Valladolid, Spain;1. School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710119, PR China;2. School of Science, Ningxia Medical University, Yinchuan 750004, PR China |
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| Abstract: | Numerical 3D simulations of turbulent, stratified two-phase shear flow with a surfactant laden interface were used to test and develop a phenomenological interfacial roughness scale model where the energy required to deform the interface (buoyancy, interfacial tension, and viscous work) is proportional to the turbulent kinetic energy adjacent to the interface.The turbulence was forced in the upper and lower liquids in the simulations, to emulate the interfacial dynamics without requiring (prohibitively) large simulation domains and Reynolds numbers. The addition of surfactant lead to an increased roughness scale (for the same turbulent kinetic energy) due to the introduction of interfacial dilatational elasticity that suppressed horizontal motion parallel to the interface, and enhanced the vertical motion.The phenomenological roughness scale model was not fully developed for dilatational elasticity in this work, but we proposed a source term that represents surfactant induced pressure fluctuations near the interface. This source term should be developed further to account for the relation between surfactant density fluctuations and turbulence adjacent to the interface. We foresee that the roughness scale model can be used as a basis for more general interfacial closure relations in Reynolds averaged turbulence models, where also mobile surfactant is accounted for. |
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| Keywords: | Two-phase turbulence modeling Interfacial closure relations Surfactant Interfacial elasticity Marangoni stress |
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