New Papers in Fluid Mechanics
Influence of confinement on the dissolution of carbon dioxide in a vertical cylindrical cell
Author(s): Daniël P. Faasen, Detlef Lohse, and Devaraj van der Meer
If carbon dioxide dissolves into a body of water, a CO2-rich boundary layer forms at the interface, which is denser in comparison to pure water, leading to the onset of buoyancy-driven convection and, consequently, the shedding of a buoyant plume. We look at the influence of confinement on this process in two ways. First, we focus on expanding our understanding of the short-time, transient diffusion of CO2 into a vertical water barrier confined to a narrow cylindrical cell. Secondly, we investigate the long-time, steady mass transfer dynamics in the liquid barrier by trapping a slug bubble underneath the liquid barrier and varying the barrier height and partial CO2 pressure.
[Phys. Rev. Fluids 9, 103501] Published Thu Oct 24, 2024
Impact of ageostrophic dynamics on the predictability of Lagrangian trajectories in surface-ocean turbulence
Author(s): Michael Maalouly, Guillaume Lapeyre, and Stefano Berti
New, high-resolution satellite altimetry is starting to reveal ocean turbulent flows at submesoscales, which are key to climate and marine ecology. However, the resulting velocity fields essentially represent the geostrophic flow component, while at these scales ageostrophic dynamics should start to become important. Using numerical simulations, we investigate the impact of unresolved ageostrophic motions on Lagrangian tracer dispersion. We find that filtering out ageostrophy only weakly affects dispersion, except for an overestimation of the typical pair-separation rate. Yet, it clearly misses transient particle clustering, which is found to be quite intense even at low Rossby numbers.
[Phys. Rev. Fluids 9, 104503] Published Thu Oct 24, 2024
Instability analysis of the effects of geothermal gradients on ${\mathrm{CO}}_{2}$-brine convection in anisotropic aquifers
Author(s): Kapil Dev and Chunendra K. Sahu
Geothermal temperature gradients may influence the fluid dynamics and convection developed during CO2 sequestration in deep saline aquifers. Here, we explore the intricate interplay in thermosolutal convection developed by vertical temperature and concentration gradients. By analyzing instability, we present insights into optimum conditions for enhanced convection and mixing between CO2 and brine.
[Phys. Rev. Fluids 9, 103803] Published Wed Oct 23, 2024
Theoretical analysis on detonation initiation induced by thermal nonuniformity in a supersonic flow
Author(s): Dehai Yu, Pengfei Yang, Lianjie Yue, and Zheng Chen
Detonation initiation induced by thermal nonuniformity in a supersonic reactive flow is analyzed with a theoretical model in one and two dimensions. A self-strengthening coupling between the reaction front and the induced shock wave is found to provide an underlying mechanism for detonation initiation. To quantify the capability of the thermal nonuniformity to cause detonation initiation, we introduce a detonation initiation factor. This factor is found to change nonmonotonically depending on the temperature difference of the thermal nonuniformity.
[Phys. Rev. Fluids 9, 103201] Published Tue Oct 22, 2024
Spatio-temporal instabilities of blood flow in a model capillary network
Author(s): Mathieu Alonzo, Nathaniel J. Karst, Thomas Podgorski, John B. Geddes, and Gwennou Coupier
The blood microcirculatory network is where nutrients, respiratory gases, and metabolic waste products are exchanged with the neighboring cells. Here, these components can take unexpected routes to get from one point to another. Whereas a simple fluid would follow the most direct route, we show in our in vitro experiments that red blood cells, which are responsible for oxygenating the body, can intermittently take side routes and remain in the network longer than expected. These observations, backed up by associated modeling, raise new questions regarding hypoxia mechanisms in organs, even under apparently healthy conditions.
[Phys. Rev. Fluids 9, 104401] Published Tue Oct 22, 2024
Fiber-flow interaction in the near field of a coaxial round jet
Author(s): Yoni Reingewirtz, David Hasin, and René van Hout
In the manufacturing process of composite materials, jet flows are commonly used to deposit anisotropic particles such as fibers. The strength or optical properties are dictated by fiber orientation, amongst others. This study investigated the motion of fibers in co-axial jet flows. In particular, the translational and rotational motion of fibers exiting from the inner jet is linked to the strong internal shear layer (ISL) existing between the fast moving outer jet and the slow moving inner jet. We show that fibers are strongly affected by the toroidal vortices in the ISL and that their translational and rotational motion can exceed that of the local fluid flow due to the “sling effect”.
[Phys. Rev. Fluids 9, 104305] Published Mon Oct 21, 2024
Turbulence in disguise: Reactive flows in porous media mimic turbulent behavior
Author(s): Emeric Boigné, Sadaf Sobhani, Joseph C. Ferguson, and Matthias Ihme
Chemically reacting flows through porous media are widespread in biological, environmental, and engineering applications. Yet, understanding these flows remains an outstanding challenging. This letter reveals that hydrodynamic dispersion affects reaction fronts in ways analogous to free turbulence. Our findings thus point to a regime diagram that elucidates the pore-scale coupling between fundamental processes, offering valuable theoretical insights into these complex flows.
[Phys. Rev. Fluids 9, L101201] Published Mon Oct 21, 2024
Influence of the vorticity-scalar correlation on mixing
Author(s): Xi-Yuan Yin, Wesley Agoua, Tong Wu, and Wouter J. T. Bos
Many factors influence the long-time behavior and mixing of a passive scalar field transported by a two-dimensional (2D) fluid flow. Our investigations based on statistical mechanics and numerical simulations suggest that the correlation of the scalar field with the flow’s vorticity field is an important factor: strong correlation with the vorticity field is detrimental to mixing. This is linked to the inverse cascade in 2D turbulence and the persistence of large scale vortical structures.
[Phys. Rev. Fluids 9, 104502] Published Fri Oct 18, 2024
Superresolution and analysis of three-dimensional velocity fields of underexpanded jets in different screech modes
Author(s): Chungil Lee, Yuta Ozawa, Takayuki Nagata, Tim Colonius, and Taku Nonomura
The present study proposes a method to estimate time-resolved three-dimensional velocity fields for underexpanded, screeching jets based on a linear stochastic estimation with non-time-resolved velocity data and time-resolved acoustic data. The proposed method can reconstruct three-dimensional velocity fluctuation fields associated with screech at the same sampling rate (200 kHz) as the microphone measurement. The azimuthal characteristics in different screech modes are investigated. We found that the flapping structure in the B mode exhibits random clockwise and counterclockwise rotations over an extended time domain. In addition, the flapping structure is first identified in the C mode.
[Phys. Rev. Fluids 9, 104604] Published Fri Oct 18, 2024
Influence of different mutual friction models on two-way coupled quantized vortices and normal fluid in superfluid $^{4}\mathrm{He}$
Author(s): Hiromichi Kobayashi, Satoshi Yui, and Makoto Tsubota
Superfluid helium consists of a mixture of inviscid superfluid and viscous normal fluid. The normal fluid is affected by quantized vortices through mutual friction. Two models have been used to describe this interaction: the two-way coupled mutual friction (2W) model using experimental parameters and the self-consistent two-way coupled mutual friction (S2W) model independent of experimental parameters. This study compares the two models in detail regarding quantized vortex ring propagation, reconnection, and thermal counterflow, and provides their advantages and limitations.
[Phys. Rev. Fluids 9, 104605] Published Fri Oct 18, 2024
Experimental observations on Weissenberg number-controlled developing turbulent boundary layers
Author(s): Zeeshan Saeed, Yasaman Farsiani, and Brian R. Elbing
Drag reduction within a turbulent boundary layer was achieved with dilute polymers that were controlled such that the Weissenberg number (Wi) was uniform in the flow. Two conditions were selected for comparison: (i) different Wi at similar drag reduction (DR) levels and (ii) different DR at comparable Wi. While the mean velocity had a secondary Wi dependence, the fluctuating statistics had a strong Wi dependence. Similarly, proper orthogonal decomposition showed the polymers deplete energy for the small scales. These trends underscore the importance of Wi when seeking a universal scaling of polymer-modified flows
[Phys. Rev. Fluids 9, 104606] Published Fri Oct 18, 2024
Instability of a vertical free convection boundary layer flow: Asymptotically from a perfectly flat one to a highly curved one
Author(s): Yang Liu and Yifeng Zhu
We investigate flow instability of the free convection boundary layer evolving along a vertical cylinder with a broad spectrum of surface curvatures. The random perturbation calculation shows that the boundary layer could filter disturbances for a high frequency band (HFB) and the single mode perturbation calculation determines the flow characteristic frequency fc. The results suggest that as curvature A increases, the characteristic frequency of the thermal boundary layer increases, while the disturbance amplitude decreases. The flow Reynolds stress is strongly amplified toward the downstream at fc and dramatically decreases at a decaying frequency fc-3.5∆.
[Phys. Rev. Fluids 9, 103901] Published Thu Oct 17, 2024
Assessment of a multiphase formulation of one-dimensional turbulence using direct numerical simulation of a decaying turbulent interfacial flow
Author(s): A. Movaghar, R. Chiodi, M. Oevermann, O. Desjardins, and A. R. Kerstein
A simple computational model simulating the evolving shape of the interface between two immiscible fluids such as oil and water in a turbulent flow has been validated using high-fidelity numerical simulations. Established theory is extended to predict that the dependencies of the smallest scale of interface wrinkling on turbulence intensity and surface tension collapse to dependence on a single parameter, involving two power-law regimes. The computational model reproduces all these features and the predicted power-law exponents. This and the other validations indicate that the model accurately represents the interaction between surface tension and turbulent fluid motion.
[Phys. Rev. Fluids 9, 104003] Published Thu Oct 17, 2024
Complexity of extreme-event prediction in turbulent flows
Author(s): Alberto Vela-Martín
The limitations of data-driven extreme-event forecasting are examined by finding the minimum computational cost of producing accurate forecasts. For this purpose, the information bottleneck method is applied to a very large dataset of direct numerical simulations of turbulent trajectories in two-dimensional Kolmogorov flow. This method is used to construct optimal models to predict extreme dissipation bursts, exploring the trade-off between model complexity and predictive skill. The results show that model complexity must increase exponentially with the forecast horizon to produce accurate predictions and that this is connected with uncertainty in the causal origin of extreme events.
[Phys. Rev. Fluids 9, 104603] Published Thu Oct 17, 2024
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