3:35pm March 7, 2018 1130 Mechanical Engineering 111 Church Street SE, Minneapolis, MN 55455 The Structure of the Turbulent Boundary Layer Along a Vertical, Surface-Piercing Plate Elias Balaras Professor; Department of Mechanical and Aerospace Engineering – The George Washington University Mechanical Engineering Department Seminar The interaction between a free surface and the turbulence beneath is central to many practical appli- cations. An example is the turbulent boundary layer on the side of a surface vessel which disturbs the air-water interface and creates a white-water region around the vessel. A canonical problem that captures the most important physical phenomena in this example is the turbulent boundary layer de- veloping along a vertical, surface-piercing flat plate moving horizontally (see figure). As of today, most of the research on this problem has focused on low Froude number regimes where the free surface stays flat. The present work reports Direct Numerical Simulations (DNS) of this problem at high Froude numbers, where the disturbances from the free-surface interact with the turbulent boundary layer. The resulting flow also leads to significant air-entrainment, which is captured by the simulations. The primary objective of the talk is to summarize the dominant flow features and their depend- ence on the Froude number in terms of velocity and vorticity statistics and spectra. We will also pro- vide detailed analysis of the different air-entrainment mechanisms and how these are related to local length and velocity scales. Bio: Elias Balaras is a Professor at the Department of Mechanical and Aerospace Engineering at the George Washington University. Dr. Balaras received his Ph.D. from the Swiss Federal Institute of Technology (EPFL) in Lausanne, Switzerland in 1995. He was formerly a visiting scientist at the National Institute for Standards and Technology and on the Faculty at the University of Maryland. He has been on the Faculty at the George Wash- ington University since January 2011. Dr. Balaras's current research program aims at the development of ro- bust numerical techniques for parallel, large-scale simulations of multiscale, multiphysics problems in physical and biological systems. Emphasis is given at large-eddy and direct numerical simulations, fluid-structure inter- actions and biological fluid dynamics. He has been the recipient of several awards including the Marie-Curie fellowship from the European Commission in 1994 and the CAREER award from the National Science Founda- tion in 2003. Dr. Balaras has published over 120 papers in refereed journals and conference proceedings, serves as an Associate Editor for the ASME J. Fluids Engineering and is a reviewer for numerous journals and government programs related to fluid mechanics, biological flows, high performance computing and turbulence. Recently his research has been featured in the New York Times and the Sunday Times.

Mechanical Engineering Department Seminar - … · 3:35pm March 7, 2018 1130 Mechanical Engineering 111 Church Street SE, Minneapolis, MN 55455 The Structure of the Turbulent Boundary

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3:35pm March 7, 2018 1130 Mechanical Engineering 111 Church Street SE, Minneapolis, MN 55455

The Structure of the Turbulent Boundary Layer Along a Vertical, Surface-Piercing Plate Elias Balaras Professor; Department of Mechanical and Aerospace Engineering – The George Washington University

Mechanical Engineering Department Seminar

The interaction between a free surface and the turbulence beneath is central to many practical appli-cations. An example is the turbulent boundary layer on the side of a surface vessel which disturbs the air-water interface and creates a white-water region around the vessel. A canonical problem that captures the most important physical phenomena in this example is the turbulent boundary layer de-veloping along a vertical, surface-piercing flat plate moving horizontally (see figure). As of today, most of the research on this problem has focused on low Froude number regimes where the free sur-face stays flat. The present work reports Direct Numerical Simulations (DNS) of this problem at high Froude numbers, where the disturbances from the free-surface interact with the turbulent boundary layer. The resulting flow also leads to significant air-entrainment, which is captured by the simula-tions. The primary objective of the talk is to summarize the dominant flow features and their depend-ence on the Froude number in terms of velocity and vorticity statistics and spectra. We will also pro-vide detailed analysis of the different air-entrainment mechanisms and how these are related to local length and velocity scales.

Bio: Elias Balaras is a Professor at the Department of Mechanical and Aerospace Engineering at the George Washington University. Dr. Balaras received his Ph.D. from the Swiss Federal Institute of Technology (EPFL) in Lausanne, Switzerland in 1995. He was formerly a visiting scientist at the National Institute for Standards and Technology and on the Faculty at the University of Maryland. He has been on the Faculty at the George Wash-ington University since January 2011. Dr. Balaras's current research program aims at the development of ro-bust numerical techniques for parallel, large-scale simulations of multiscale, multiphysics problems in physical and biological systems. Emphasis is given at large-eddy and direct numerical simulations, fluid-structure inter-actions and biological fluid dynamics. He has been the recipient of several awards including the Marie-Curie fellowship from the European Commission in 1994 and the CAREER award from the National Science Founda-tion in 2003. Dr. Balaras has published over 120 papers in refereed journals and conference proceedings, serves as an Associate Editor for the ASME J. Fluids Engineering and is a reviewer for numerous journals and government programs related to fluid mechanics, biological flows, high performance computing and turbu-lence. Recently his research has been featured in the New York Times and the Sunday Times.