J. Thomas 2016 : Resonant fast-slow interactions and breakdown of quasi-geostrophy in rotating shallow water, J. Fluid. Mech., 788: 492-520. PDF
Summary: This paper examines interactions between fast inertia-gravity waves and slow balanced flows using asymptotic analysis. An evolution equation is derived for the slow dynamics to show that fast waves can energetically interact with balanced fields. In particular, an elegant toy model is developed in this paper to show that models that ignore fast wave dynamics can lead to wrong predictions on long time scales.
 J. Thomas, K. S. Smith and O. Buhler 2017: Near-inertial wave dispersion by geostrophic flows J. Fluid. Mech., 817: 406-438. PDF
Summary: This paper investigates interactions between near-inertial waves and mesoscale eddies using asymptotic analysis and three dimensional numerical simulations. It is shown that reduced asymptotic models can capture intricate features of the near-inertial waves, thus substituting complex and expensive three dimensional equations.
 J. Thomas 2017: New model for acoustic waves propagating through a vortical flow J. Fluid. Mech., 823: 658-674. PDF
Summary: A new amplitude equation is derived in this paper for high-frequency acoustic waves propagating through an incompressible vortical flow. The reduced model is specifically suited to capture the features of the wave field in the regime where the spatial scales of the wave and vortical field are comparable, a regime for which an optimal reduced model was unavailable.
 J. Thomas, O. Buhler and K. S. Smith 2018: Wave induced mean flows in rotating shallow water with uniform potential vorticity J. Fluid. Mech., 839: 408-429. PDF
Summary: Numerical simulations and multiple asymptotic models are used to investigate qualitative and quantitative features of wave-induced mean flows generated by gravity waves in the absence of potential vorticity. Specific detailed changes in the flow field are examined as the rotation rate decreases, indicative of the scenario on moving from large mesoscales to small submesoscales in the ocean.
 J. Thomas and R. Yamada 2018: An amplitude equation for surface gravity wave-topography interactions Phys. Rev. Fluids, 3, 124802. PDF
Summary: A new reduced model is derived in this paper to capture the interaction of surface gravity waves with bottom topography. The new model is capable of capturing complex and intricate features of the wave field, such as wave focusing and scattering, these being compared with high resolution numerical simulations of three dimensional nonlinear water wave equations.
 J. Thomas and R. Yamada 2019: Geophysical turbulence dominated by inertia-gravity waves. J. Fluid. Mech., 875: 71-100. PDF
Summary: Inspired by recent observations and global-scale simulations that show the dominance of low-mode internal tides at 100 km scales in certain oceanic regions, this paper examines the effect of high frequency inertia-gravity waves on small Rossby number geostrophic turbulence. We uncover a new geophysical turbulence phenomenology in wave dominated regions and thereby expand the scope of two-mode quasi-geostrophic turbulence by including low-mode internal tides in the turbulence paradigm.
 J. Thomas and S. Arun 2020: Near-inertial waves and geostrophic turbulence. Phys. Rev. Fluids, 5, 014801. PDF
Summary: The two-mode quasi-geostrophic model is the holy grail of geophysical turbulence in the small Rossby number regime. Yet it completely excludes high energy near-inertial waves which are ubiquitous in the upper ocean. In this paper we expand the scope of two-mode geostrophic turbulence by including high energy near-inertial waves. The paper explains how near-inertial waves can significantly alter the well established quasi-geostrophic turbulence paradigm.
 J. Thomas and D. Daniel 2020: Turbulent exchanges between near-inertial waves and balanced flows J. Fluid. Mech. 902, A7. PDF
Summary: The strength of wind generated near-inertial waves and balanced flow varies both geographically and seasonally over the world’s oceans. In this paper we use high resolution numerical simulations of the three dimensional Boussinesq equations to examine directions of energy flow in turbulent interactions between waves and balanced flows. The manuscript describes how wave-balance energy flow pathways change as a function of relative strengths of wave and balanced fields. Depending on the balance-to-wave energy ratio, near-inertial waves can act as an energy sink or energy source for the geostrophic balanced flow.
 J. Thomas and D. Daniel 2021: Forward flux and enhanced dissipation of geostrophic balanced energy J. Fluid. Mech. 911, A60. PDF
Summary: Flows in the ocean is a mixture of fast evolving internal gravity waves and slowly evolving gesotrophic vortices. Oceanographers often speculate that internal gravity waves could form an energy sink for the geostrophic balanced flow. This paper illustrates a mechanism by which internal waves can trigger a forward flux of balanced energy and explains that the direction of wave-balance energy exchange is senitive to the parameter regime. Table 2 in the paper lists the summary of wave-balance energy exchanges in different regimes.
 J. Thomas and A. Gupta 2022: Wave-enhanced tracer dispersion JGR Oceans 127, e2020JC017005. PDF
Summary: Internal gravity waves are often considered to be inefficient in stirring tracers in the ocean. This paper shows that waves can modify the slow balanced flow, which then stirs tracers more efficiently when compared to tracer stirring by a balanced flow in the absence of waves. Therefore waves can indirectly enhance tracer stirring in the ocean. Figure 8 shows a schematic of the main result of the paper.
 J. Thomas and R. Vishnu 2022: Turbulent transition of a flow from small to O(1) Rossby numbers J. Phys. Oceanography 52, 2609-2625. PDF
Summary: This paper examines the effect of a low energy unbalanced perturbation on an energetic balanced flow as a function of Rossby number. Erosion of coherent vortices, persistence of cyclonic vortices over anticyclonic vortices, increased forward flux and enhanced dissipation of the flow energy are notable features seen as Rossby number increases. The study finds a striking result that even a small unbalanced perturbation can do increasingly more damage to the balanced flow as Rossby number increases from asymptotically small to O(1) values.
 J. Thomas and L. Ding 2023: Upscale transfer of waves in one dimensional rotating shallow water J. Fluid Mech. 961, A2. PDF
Summary: This paper shows that waves in rotating shallow water can exhibit an inverse flux due to conservation of wave action along with wave energy. Comparisons are made between theoretical predictions based on wave turbulence theory and direct numerical simulation results. The results point out that intermittency and non-Gaussian effects lead to solutions that are different from those predicted by wave turbulence theory.
 J. Thomas and R. Camassa 2023: The self-induced flow over a cylinder in a stratified fluid J. Fluid Mech. 964, A38. PDF
Summary: Bodies immersed in a stratified fluid can lead to the generation of a low-Rynolds number flow around them. This paper derives the flow field around a cylinder immersed in a stratified fluid and shows that the self-induced flow decays much slower when compared to the far-field decay rate of Stokes velocity generated by a slow moving cylinder in an unstratified fluid.
 J. Thomas 2023: Turbulent wave-balance exchanges in the ocean, To appear in Poceedings of the Royal Society A.