Santiago J. Benavides

Research

Turbulent cascades and phase dynamics

Turbulent flows transfer energy across scales in what is known as a turbulent energy cascade. The turbulent energy cascade in two-dimensional and geophysical flows is strikingly different from that of isotropic three-dimensional flows. My research aims to uncover the mechanisms which drive the energy cascade in these various settings and understand what causes the observed change in behavior. In particular, I focus on the role that triad phases play in the energy cascade.

Collaborators: Miguel Bustamante, Alexandros Alexakis , Kannabiran Seshasayanan, François Pétrélis.

Transition to turbulence and wall-bounded shear flows

Wall-bounded shear flows, such as pipe flow or the flow between to plates, exhibit striking large-scale patterns that emerge at different flow speeds. In plane Couette flow, oblique laminar-turbulent bands appear at low speeds (see figure below), whereas at high speeds flow-aligned 'roller' vortices span the whole domain. My research aims to understand why these patterns form and what sets their properties, such as angle and length-scales.

Collaborators: Dwight Barkley, Laurette Tuckerman, Javier Jiménez,

Sediment transport

In bed load sediment transport, grains are moved by turbulent flow and are in nearly continuous contact with other grains. Despite their chaotic and unpredictable trajectories, each individual grain ultimately contributes to the ordered, large-scale properties of the river they are a part of - from the way it transports sediment to its width and shape. My research aims to understand this connection from grain to river scales using a series of intermediate-complexity models and simplified statistical approaches.

Collaborators: J. Taylor Perron, Eric Deal, Jeremy G. Venditti

Turbulence in the transition region of gas giant planets and exoplanets

Ionization occurs in the upper atmospheres of hot Jupiter exoplanets and in the interiors of gas giant planets, leading to magnetohydrodynamic (MHD) effects which couple the momentum and the magnetic field, thereby significantly altering the dynamics. In the transition region between the hot, ionized interior and cold, neutral region, one finds moderate temperatures such that the gas is only partially ionized and very poorly conducting. The transition region acts as a bottom boundary for the atmospheric jets seen on the surface, and as a top boundary for the magnetid-field generating dynamo region. It therefore likely affect things like the depths of the jets or the morphology of the magnetosphere. In my work, I use idealized turbulence simulations to understand how the particular characteristics of this region (partial ionization and weak conductivity) affect the dynamics and could therefore influence the formation of jets and more.

Collaborators: Glenn R. Flierl, Keaton J. Burns, Basile Gallet

Journal publications & preprints

• "Phase dynamics and their role determining energy flux in hydrodynamic shell models,"
  Benavides, S. J., & Bustamante, M. D. (arXiv), 2025. [preprint]
• "Intermittent grain activity from grain-scale collective entrainment rules,"
  Benavides, S. J., Deal, E., Venditti, J.G. & Perron, J. T. (Submitted to Journal of Geophysical Research: Earth Surface), 2025. [preprint]
• "Model for transitional turbulence in a planar shear flow,"
  Benavides, S. J., & Barkley, D. (arXiv), 2025. [preprint]
• "Discrete Simulations of Fluid‐Driven Transport of Naturally Shaped Sediment Particles,"
  Zhang, Q., Deal, E., Perron, J. T., Venditti, J. G., Benavides, S. J., Rushlow, M., & Kamrin, K. Journal of Geophysical Research: Earth Surface, 130, 5, e2024JF007937, 2025. [preprint] [doi]
• "How fast or how many? Sources of sediment transport intermittency,"
  Benavides, S. J., Deal, E., Venditti, J.G., Zhang, Q., Kamrin, K., & Perron, J. T. Geophysical Research Letters, 50, e2022GL101919, 2023. [preprint] [doi]
• "Grain shape effects in bed load sediment transport,"
  Deal, E., Venditti, J.G., Benavides, S. J., Bradley, R., Zhang, Q., Kamrin, K. & Perron, J. T. Nature, 613, 298-302, 2023. [preprint] [doi]
• "Effective drag in rotating, poorly conducting plasma turbulence,"
  Benavides, S. J., Burns, K. J., Gallet, B., & Flierl, G. R. The Astrophysical Journal, 938, 92, 2022. [arxiv] [doi]
• "Fluid-driven transport of round sediment particles: from discrete simulations to continuum modeling,"
  Zhang, Q., Deal, E., Perron, J. T., Venditti, J. G., Benavides, S. J., Rushlow, M., & Kamrin, K. JGR: Earth Surface, 127, e2021JF006504, 2022. [preprint] [doi]
• "Inverse cascade suppression and shear layer formation in MHD turbulence subject to a guide field and misaligned rotation,"
  Benavides, S. J., Burns, K. J., Gallet, B., Cho, Y-K., & Flierl, G. R. Journal of Fluid Mechanics, 2022. [arxiv] [doi]
• "The impact of intermittency on bed load sediment transport,"
  Benavides, S. J., Deal, E., Rushlow, M., Venditti, J.G., Zhang, Q., Kamrin, K., & Perron, J. T. Geophysical Research Letters, 49, e2021GL096088, 2022. [preprint] [doi]
• "Symmetry breaking in a turbulent environment,"
  Alexakis, A., Pétrélis, F., Benavides, S. J., & Seshasayanan, K. Phys. Rev. Fluids, 2021. [arxiv] [doi]
• "Two-dimensional partially ionized magnetohydrodynamic turbulence,"
  Benavides, S. J. & Flierl, G. R. Journal of Fluid Mechanics, 2020. [arxiv] [doi]
• "Critical transitions in thin layer turbulence,"
  Benavides, S. J. & Alexakis, A. Journal of Fluid Mechanics, 2017. [arxiv] [doi]
• "On the edge of an inverse cascade,"
  Seshasayanan, K., Benavides, S. J. & Alexakis, A. Physical Review E, 2014. [arxiv] [doi]

• September 1, 2025 I am very pleased to announce that I have started my position as Lecturer in Applied and Computational Mathematics at the University of Edinburgh!
• May 2, 2023 I am very pleased to announce that I have received the Marie Sklodowska-Curie European Postdoctoral Fellowship! I will be working with Javier Jiménez at the Universidad Politécnica de Madrid and Miguel Bustamante at the University College Dublin on "Elucidating the bidirectional energy cascade of geophysical turbulence in time, space, and scale". I am very excited to begin in September of 2023.
• January 25, 2022 My paper with Keaton Burns, Basile Gallet, James Cho, and Glenn Flierl, Inverse cascade suppression and shear layer formation in MHD turbulence subject to a guide field and misaligned rotation, has finally been published in the Journal of Fluid Mechanics. Take a look here!
• December 15, 2021 I successfully passed my thesis defense! Send me an email if you are interested in a copy of my thesis. It's been a great five and a half years at MIT; I've learned and grown so much! I'm so thankful for all of the support I've had from my friends, advisors, and my partner during this time. I will miss Boston, but I am very excited to get going on the next step!
• December 13, 2021 I can finally officially announce that I have accepted a post doc position at the University of Warwick, where I will work with Dwight Barkley and Laurette Tuckerman on problems related to transition to turbulence in wall-bounded shear flows.
• August 11, 2020 My first PhD paper with Glenn Flierl, Two-dimensional partially ionized magnetohydrodynamic turbulence, has finally been published in the Journal of Fluid Mechanics. Take a look here!
• June 15, 2020 I am honored to have been awarded NASA's Future Investigators in NASA Earth and Space Science and Technology (FINESST) fellowship , which will fund me for my last year of my PhD!
• June 13, 2020 My article with Glenn Flierl on "two-dimensional, partially-ionized, magnetohydrodynamic turbulence" has been accepted by the Journal of Fluid Mechanics for publication.
• June 1, 2020 Day 1 of summer mentorship! This summer I will be mentoring and working with two undergraduate research interns from MIT, who will be working on a project with Glenn Flierl and I on rotating convection. I look forward to teaching them about fluid dynamics, convection, and numerical simulations, but most importantly I look forward to collaborating with future scientists in the field!