Article
Mechanics
H. Lam, A. Delache, F. S. Godeferd
Summary: Direct numerical simulations of rotating turbulence were conducted, separating the velocity field into inertial waves, eddies, and a geostrophic mode. The interactions and energy transfers among them were analyzed, providing insights into the mechanisms involved.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jim Thomas, Lingyun Ding
Summary: We investigate the inverse flux of waves in a one-dimensional rotating shallow water model, a simplified geophysical fluid dynamics model. By directly integrating the governing equations, we observe that waves injected at small scales primarily transfer upscale through resonant quartic interactions between wave modes. The upscale transfer of waves is found to be non-local and involves turbulent transfer between different scales of the flow. Our analysis reveals intermittent bursts in wave action flux, resulting in a shallower wave spectrum and higher amplitude wave fields in physical space. Additionally, statistics of the flow fields indicate that lower energy high wavenumbers follow the assumptions of wave turbulence theory, while non-uniform wave phase distribution and non-Gaussian statistics dominate at larger scales or low wavenumbers containing the majority of the flow energy. These findings highlight the complex and intricate features associated with the upscale transfer of waves in the simple geophysical fluid dynamic model of one-dimensional rotating shallow water that have not been previously recognized.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Optics
Julian Amette Estrada, Marc E. Brachet, Pablo D. Mininni
Summary: Quantum turbulence in rotating condensates is fundamentally different from classical turbulence. It exhibits negative temperature state, self-organization of kinetic energy in quantized vortices, and a non-Kolmogorovian scaling of energy at small scales.
Article
Mechanics
L. Oruba, A. M. Soward, E. Dormy
Summary: This paper investigates the primary quasi-steady geostrophic motion of a constant density fluid in a rotating cylindrical container through direct numerical simulation, revealing significant inertial wave activity. Building on previous results for an infinite plane layer, the study provides analytical insights into the inertial wave generation triggered by the QG-flow and lateral boundary effects.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Nathan E. Grube, M. Pino Martin
Summary: The study explores the discrepancy between theoretical predictions and computational/experimental results regarding the Reynolds stress tensor in vortical turbulence interacting with a normal shock wave at Mach 2 or greater. It is found that the redistribution of energy between transverse and streamwise Reynolds stresses is influenced by the wavelengths of the vortical waves emitted during the interaction, leading to the dominance of R-11. A quantitative model based on this understanding of flow physics accurately predicts anisotropy levels observed in direct numerical simulation data.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Weibo Hu, Stefan Hickel, Bas W. van Oudheusden
Summary: This study investigates the low-frequency unsteady motions and vortex phenomena behind a backward-facing step in a turbulent flow using large-eddy simulation. The interaction between shock wave and separated shear layer, shedding of shear layer vortices, and Gortler-like vortices influenced by fluctuations in the incoming boundary layer are key findings. Comparison with a laminar case and observations of slightly higher non-dimensional frequency in the low-frequency mode provide valuable insights.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Matthew N. Crowe, Cameron J. D. Kemp, Edward R. Johnson
Summary: This study models the decay of Hill's vortex in a weakly rotating flow, deriving analytic results for the modification of the vortex structure by rotational effects and the generated wave field. Predictions for the decay of vortex speed and radius are made using an asymptotic approach, and results are compared against numerical simulations of the full axisymmetric Navier-Stokes equations.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Benjamin K. K. Smeltzer, Olav Romcke, R. Jason Hearst, Simen A. Ellingsen
Summary: When surface waves interact with ambient turbulence, turbulent eddies get redirected, intensified and periodically stretched and compressed, while the waves suffer directional scattering. In this study conducted at the Norwegian University of Science and Technology (NTNU), the mutual interactions between surface waves and turbulence were experimentally studied in a water channel laboratory. The experimental results showed that there was a strong enhancement of streamwise vorticity near the surface, in agreement with theory, and that the directional wave spectrum broadened with increasing propagation distance.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Nathan E. E. Grube, M. Pino Martin
Summary: Recent direct numerical simulation studies have shown that in highly compressible regime, the amplification of streamwise Reynolds stress in canonical shock-isotropic turbulence interactions (SITIs) is higher than in previous studies. This can be explained by the relatively high Mach number and significant dilatational energy in the incident flow. Loss of amplification is observed as the flow parameters approach the threshold between wrinkled and broken shock regimes due to highly perturbed shock structure. The proposed parametrization based on root-mean-square Mach number fluctuation improves the collapse of shock structure data, suggesting its applicability to general isotropic inflow fields.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Michael R. R. Cox, Hossein A. A. Kafiabad, Jacques Vanneste
Summary: The dispersion of three-dimensional inertia-gravity waves by a turbulent geostrophic flow leads to a diffusion process in wavevector space. Previous studies have obtained the diffusivity tensor assuming a time-independent geostrophic flow. This study relaxes this assumption and examines how the weak diffusion of wave action affects the distribution of wave energy due to the slow time dependence of the geostrophic flow. The results show that the wave-energy spectrum is localized within a thin boundary layer around the constant-frequency cone, with its thickness controlled by the acceleration spectrum of the geostrophic flow.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Clara M. Helm, M. Pino Martin, Owen J. H. Williams
Summary: This study provides a detailed characterization of the shear layer in three separated shock/turbulent boundary layer interactions, showing similarities with canonical compressible mixing layers. The study also reveals the behavior of turbulence energy transfer in the shear flow, emphasizing the importance of studying shock/turbulent boundary layer interactions in this manner.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Giovanni Dematteis, Yuri V. Lvov
Summary: We calculate the net energy per unit time exchanged between two sets of modes in a generic system using a three-wave kinetic equation. Our method allows for quantifying the energy transfers in isotropic and anisotropic wave systems, providing a systematic approach to energy fluxes in wave turbulence. It is not limited to stationarity, scale invariance, and strict locality, and has potential implications in the interpretation of wave turbulence experiments.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jim Thomas, Don Daniel
Summary: A study on the interaction between internal gravity waves and geostrophic balanced flow in the world's oceans reveals significant variability in energy balance, with wave-dominated regions showing an overtaking of the wave spectrum over the balanced flow at mesoscales. The research demonstrates that in high wave energy regions, waves can reverse the direction of geostrophic energy flux, leading to enhanced geostrophic energy dissipation.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Yulin Pan, Patrick J. Haley, Pierre F. J. Lermusiaux
Summary: This study examines the interactions of internal tides (ITs) with a dynamic, rotational, and heterogeneous ocean, as well as spatially varying topography. It investigates the significant interactions of ITs with background fields, particularly at topographic features and strong currents, when the scales of the background and ITs are similar. The study also explores the modulation of wavenumber and energy of ITs propagating into collinear and opposing currents, providing insights into wave behaviors and critical opposing current speeds triggering wave focusing/blocking phenomena.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Gregory LeClaire Wagner, Nick Pizzo, Luc Lenain, Fabrice Veron
Summary: This paper investigates the complex chain of events that occur when a light breeze causes ripples on calm water, eventually leading to the formation of a turbulent shear layer. The study compares laboratory experiments with numerical simulations and validates the wave-averaged model. However, the simulations also reveal a sensitivity to the prescribed surface wave amplitude.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Fluids & Plasmas
Jiro Mizushima, Kazuki Abe, Naoto Yokoyama
PHYSICAL REVIEW FLUIDS
(2017)
Article
Physics, Fluids & Plasmas
Naoto Yokoyama, Masanori Takaoka
PHYSICAL REVIEW FLUIDS
(2017)
Article
Mechanics
Mitsuhiro Tanaka, Naoto Yokoyama
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2018)
Article
Engineering, Aerospace
Jeeva Jayakumar, Kei Senda, Naoto Yokoyama
JOURNAL OF AIRCRAFT
(2018)
Article
Mechanics
Jiro Mizushima, Rei Matsuda, Naoto Yokoyama
FLUID DYNAMICS RESEARCH
(2019)
Article
Physics, Fluids & Plasmas
Naoto Yokoyama, Masanori Takaoka
PHYSICAL REVIEW FLUIDS
(2019)
Article
Biology
Naoto Yokoyama, Naoki Takeishi, Shigeo Wada
Summary: The importance of CSF flow in the PVS surrounding brain arteries is widely debated, with numerical simulations showing that arterial pulsation can generate net CSF flow velocity, although the peak velocity is two orders of magnitude higher. Interestingly, the net CSF flow velocity aligns with the analytical solution derived from lubrication theory, similar to Taylor's swimming sheet model.
JOURNAL OF THEORETICAL BIOLOGY
(2021)
Article
Physics, Fluids & Plasmas
Naoto Yokoyama, Hiroshi Yamashita, Kento Higashi, Yuta Miki, Tomoaki Itano, Masako Sugihara-Seki
Summary: Experimental and numerical studies on particle focusing in a square-tube flow revealed that the focusing patterns depend on polymer concentration, with transitions among patterns being driven by elastic forces due to the first normal stress difference and polymer elongation.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Chemistry, Analytical
Naoki Takeishi, Hiroshi Yamashita, Toshihiro Omori, Naoto Yokoyama, Masako Sugihara-Seki
Summary: This study numerically investigated the behavior of single red blood cells in a circular microchannel, revealing that the axial or nonaxial migration of red blood cells depends on their stable deformed shapes, and the equilibrium radial position of the red blood cell centroid correlates well with energy expenditure associated with membrane deformations.
Article
Physics, Fluids & Plasmas
Masanori Takaoka, Naoto Yokoyama, Eiichi Sasaki
Summary: Local-flux vectors of conserved quantities are proposed to investigate the directional properties of anisotropic turbulence. The vectors are validated in statistically steady states of Charney-Hasegawa-Mima turbulence, showing consistency with the energy-enstrophy double cascade in 2D isotropic turbulence.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
Naoki Takeishi, Hiroshi Yamashita, Toshihiro Omori, Naoto Yokoyama, Shigeo Wada, Masako Sugihara-Seki
Summary: This study numerically analyzed the lateral movement and equilibrium radial positions of red blood cells in a circular channel, revealing bistable flow modes (rolling and tumbling) with different equilibrium radial positions.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Makoto Iima, Naoto Yokoyama, Kei Senda
Article
Physics, Fluids & Plasmas
Naoto Yokoyama, Masanori Takaoka
Proceedings Paper
Mathematics, Applied
Masanori Takaoka, Naoto Yokoyama
3RD INTERNATIONAL CONFERENCE ON MATHEMATICAL MODELING IN PHYSICAL SCIENCES (IC-MSQUARE 2014)
(2015)