Tootfinder

Interesting proposal on splitting the single German bidding zone: joining the North with western Denmark.
What I find appealing about it (alongside the reality of ⚡ flows): a smaller role for national politics, whilst strengthening pan-European planning and independent regulatory oversight.

Vorstoß für gemeinsame Stromzone mit Westdänemark

I do love how reflective the sand gets at low tide (Coolum Beach).

Sources: Chinese regulators have told banks to back tech companies, but lenders still prefer stable cash flows and profitability over loss-making tech startups (Bloomberg)
https://www.bloomberg.com/news/features/2026-0…

We are living in a new world of hedgers.
The shocks of the last several years
—COVID-19, Russia’s war in Ukraine,
Trump’s tariffs,
and the Iran conflict
—have upended how nations approach international affairs.
The smooth flows of a globalized and rules-based world have clotted into uncertainty,
forcing states to find new pathways for trade, diplomacy, resource extraction, and defense cooperation.
Countries no longer consider historical partner…

Hedging Is the New Normal
For the foreseeable future, successful statecraft will depend on hedging.

New NERDS paper on drug traffic and migration
https://nerds.itu.dk/2026/06/01/nerds-paper-on-drug-traffic-and-migration/

The #Niobrara National Scenic River, northern #Nebraska, at the Hwy 183 bridge. It flows eastward to join with the Missouri.

Battery Sounds: How Does a Battery Sound in Time-lapse? - Audification: listening to my Enphase AC Battery state of charge and flows #podcast #audification #battery -

Battery Sounds: How Does a Battery Sound in Time-lapse?
Audification: listening to my Enphase AC Battery state of charge and flows #podcast #audification #battery

Climate solutions in action this week:
California Resources Corp is opening the state's first CO2 storage site in a depleted oil field—creating permanent geologic storage for industrial emissions.
Recife, Brazil launched a public-private initiative financing collection, sorting, and recycled-content markets to build a circular plastics economy.
Real progress, happening now.
Sign up for the For People And Planet climate solutions digest:

Weekly Climate Solutions Digest
Welcome This week, the stories share a theme: coordination at scale and giving old systems new work. Across continents, we bank energy, pool flexibility, and clean up the flows of goods and carbon. The arc is steady & practical: take what we have, connect it, and make it serve a cleaner

Fascinating probability analysis of English council election voter flows (2024/2026).
https://oskanberg.github.io/2026-voter-flows/
H/T @…

Does anyone know where I can find daily historic #isobar charts for the #UK? I want to study wind flows across #Britain during the three heatwaves we've had so far this year.

From Flows to Maps: Sampling Laws for Attractor Intensity and Bounded-Noise Escape
Jiguang Yu, Louis Shuo Wang
https://arxiv.org/abs/2608.02933 https://arxiv.org/pdf/2608.02933 https://arxiv.org/html/2608.02933
arXiv:2608.02933v1 Announce Type: new
Abstract: Intensity of attraction quantifies the largest amplitude of a persistent bounded disturbance that an attractor can withstand without loss of controlled confinement in its basin. Although intensity has been formulated separately for flows and maps, its behavior under temporal sampling has remained unresolved. We establish an explicit correspondence between the intensity $\mu(A)$ of a continuous-time attractor and the intensity $\mu_h(A)$ of its exact time-$h$ map. For an $L$-Lipschitz vector field, \[ \frac{\mu(A)}{1 Lh} \leq \frac{\mu_h(A)}{h} \leq \mu(A)\frac{e^{Lh}-1}{Lh}, \] and hence $\mu_h(A)/h\to\mu(A)$. The resulting first-order rate is sharp in general, while smooth scalar escape geometries can exhibit second-order convergence. We extend the framework to one-step numerical methods through a stability theory for block intensity and to attracting invariant graphs over compact invertible nonautonomous bases, obtaining uniform sampling convergence over the forcing phase. For bounded-support random perturbations, normalized discrete intensity is identified with the pathwise safety threshold; above it, finite escape follows under an explicit finite-exit condition, while escape probabilities require additional assumptions on the noise law. We also show that the discrete state--normal boundary map converges to the normalized Pontryagin boundary system governing extremal reachable-set boundaries. Exact scalar benchmarks, a grazing resilience model, planar Duffing escape, anisotropic disturbances, periodic and quasiperiodic forcing, and transfer-operator computations illustrate the theory. These results give intensity estimated from discrete observations or simulations a sampling-independent continuous-time meaning.
toXiv_bot_toot

Three-layer water flows: Dirichlet-Neumann operators and approximations
Rossen Ivanov, Calin-Iulian Martin
https://arxiv.org/abs/2608.06314 https://arxiv.o…

Cosmic Velocity Flows: from Theory to Observations
Saee Dhawalikar
https://arxiv.org/abs/2608.03530 https://arxiv.org/pdf/2608.03530 https://arxiv.org/html/2608.03530
arXiv:2608.03530v1 Announce Type: new
Abstract: The Large-Scale Structure (LSS) of the Universe forms a complex network of nodes, filaments, sheets, and voids known as the Cosmic Web. As current and upcoming galaxy surveys increasingly probe the quasi-linear and non-linear regimes of structure formation, understanding its geometry and dynamics is essential for precision cosmology. In particular, cosmic filaments, which channel matter across the web, are central to these dynamical processes.
This thesis develops numerical tools to study the non-linear cosmic web. First, the Sahyadri suite of high-resolution cosmological $N$-body simulations is introduced, providing a framework for precision studies of LSS and its cosmological dependence. A calibration framework for filament reconstruction is then developed using controlled filament realizations, enabling systematic investigation of reconstruction biases. The effects of filament curvature and reconstruction noise on inferred filament properties are quantified, and a novel Fourier-space smoothing approach is introduced to improve profile recovery.
The thesis further presents Skeletor, a Voronoi-based filament finder that identifies filamentary structures directly from discrete tracers while explicitly incorporating the hierarchical nature of the cosmic web. A novel framework for classifying sub-filamentary structure is developed. Applying these tools to cosmological simulations reveals distinct properties of filament substructure and provides a detailed view of filament phase space, including coherent inflows, multistreaming, and caustic-like features.
Together, these developments provide a framework for studying the geometry, hierarchy, and dynamics of the non-linear cosmic web. More broadly, they contribute to the ongoing effort to build a physically motivated understanding of the non-linear cosmic web beyond traditional measures of clustering.
toXiv_bot_toot

It's #WaterfallWednesday and this one came to my mind. You might see a nice waterfall. I spent 3h there. Really! In hindsight I didn't know where all the time went but I enjoyed seeing the #waterfall from all kinds of angles and shutter speeds.
3h very well invested liveti…

This week: real climate coordination at scale.
The EU set a 2030 energy storage target to cut gas reliance. The Next Generation Shipping Act would invest $1B/year in zero-emission vessels and port electrification. Recife launched a circular plastics initiative to finance collection and reuse systems.
Sign up for the For People And Planet climate solutions digest.

Weekly Climate Solutions Digest
Welcome This week, the stories share a theme: coordination at scale and giving old systems new work. Across continents, we bank energy, pool flexibility, and clean up the flows of goods and carbon. The arc is steady & practical: take what we have, connect it, and make it serve a cleaner

No Silver Bullet, But a Silver Lining? PETs and International Data Transfers
https://fpf.org/blog/no-silver-bullet-but-a-silver-lining-pets-and-international-data-transfers/
@…

Battery Sounds: How Does a Battery Sound in Time-lapse? - Audification: listening to my Enphase AC Battery state of charge and flows #podcast #audification #battery -

Battery Sounds: How Does a Battery Sound in Time-lapse?
Audification: listening to my Enphase AC Battery state of charge and flows #podcast #audification #battery

#PhDCongratulations!!! 🥳 As the 250th graduate of the @…, Ilse de Langen successfully defended her thesis today. Title: Modelling Magnetic Induction and Lorentz Force-Driven Flows in Europa’s Subsurface Ocean

Komuro Expansivity and Periodic Orbit Growth for Multi-Singular Hyperbolic Flows
Maria Jos\'e Pacifico, Fan Yang, Jiagang Yang, Rusong Zheng
https://arxiv.org/abs/2608.02186 https://arxiv.org/pdf/2608.02186 https://arxiv.org/html/2608.02186
arXiv:2608.02186v1 Announce Type: new
Abstract: In this paper we prove that every multi-singular hyperbolic set of a $C^1$ flow is Komuro expansive. This is the strongest natural form of expansivity for flows with singularities accumulated by regular orbits, allowing arbitrary orientation-preserving time reparametrizations. We then use this to establish a two-sided asymptotic counting bound of the form $e^{ht}/t$ for periodic orbits, and prove that the normalized orbit measures converge to the unique measure of maximal entropy. We also establish the same results for a $C^1$ open and dense subset of star vector fields.
toXiv_bot_toot

Replaced article(s) found for physics.app-ph. https://arxiv.org/list/physics.app-ph/new
[1/1]:
- Hydrodynamic Behavior of Non-spherical Particles in Confined Vertical Flows: A Resolved CFD-DEM S...
Das, Choudhury, Jaggannagari, Krishnan, Kuttikrishnan, Ramakrishnan, Annabat…

Onsager-variational-principle-based Lattice Boltzmann Model For Three-phase Dielectric Fluid Flows
Xinyue Liu, Xu Qian, Fang Xiong, Lei Wang
https://arxiv.org/abs/2608.05787 htt…

From Interfilamentary Gas to Filaments and Hubs - Gas Flows in the Monoceros R2 Hub–Filament System: #StarFormation: https://www.kyushu-u.ac.jp/en/researches/view/407

from my link log —
Modelling BBR's interactions with traditional TCP loss-based congestion control.
https://blog.apnic.net/2020/01/24/modelling-bbrs-interactions-with-loss-based-congestion-control/
saved 2020-01-25 …

Modelling BBR’s interactions with loss-based congestion control | APNIC Blog
Guest Post: While BBR is supposed to be a rate-based algorithm, when competing with other flows, BBR is window-limited.

#rstats mapgl is now on CRAN with flowmaps support! As previewed at #MobileTartu (Mobility Lab, University of Tartu) and Association of Geographic Information Laboratories in Europe (#AGILE) conferences! (Video by Kyle Walker). Backend is Flowmap.gl

What is the Source?
To the painter Remedios Varo, and possibly to Thomas Cole (founder of the Hudson River school), the Source was an overflowing chalice set in a mysterious landscape.
The Source is magical and inexhaustible (like a fairy-tale soup pot), hidden and yet waiting to be found, ready to be discovered not once but endlessly.

Lake Tear of the Clouds
What is the Source? On Thomas Cole, Remedios Varo, Verplank, Colvin, Lake Tear of the Clouds, and the Hudson, the river that flows both ways.

Iranian Strikes on Ships Test Cease-Fire and Threaten Energy Flows in Gulf (New York Times)
https://www.nytimes.com/2026/07/07/world/middleeast/iran-war-oman-hormuz-tanker.html
http://www.memeorandum.com/260707/p11#a260707p11

🇺🇦 #NowPlaying on #BBC6Music's #LaurenLaverne
Glass Animals:
🎵 Gooey
#GlassAnimals
https://ihfmusic.bandcamp.com/track/glass-animals-gooey-imagined-herbal-flows-remix
https://open.spotify.com/track/1gk3FhAV07q9Jg77UxnVjX

Conditional Normalizing Flow for Gas-Surface Scattering from Thermal to Hypersonic Velocities
Miklas Sch\"utte, Stephen Hocker, Hansj\"org Lipp, Johannes Roth, Stefanos Fasoulas, Marcel Pfeiffer
https://arxiv.org/abs/2606.31928 https://arxiv.org/pdf/2606.31928 https://arxiv.org/html/2606.31928
arXiv:2606.31928v1 Announce Type: new
Abstract: Accurate aerodynamic modeling of satellites in very low Earth orbit (VLEO) requires gas-surface interaction (GSI) models that capture the full velocity spectrum from thermal to orbital speeds. Atmospheric particles initially strike spacecraft surfaces at hypersonic velocities of 6 000 - 10 000 m/s. Due to surface roughness and complex geometries, especially within air-breathing electric propulsion (ABEP) intake systems, multiple collisions occur, progressively reducing the particle velocities. A recent machine learning framework for deriving scattering kernels from molecular dynamics (MD) simulations has shown promise, but remains limited to high-velocity single impacts and possibly violates fundamental equilibrium principles such as detailed balance. This work extends this machine learning based scattering kernel to cover the complete velocity range using conditional normalizing flows trained with physics-informed constraints, enabling accurate modeling of multi-bounce scenarios in realistic VLEO applications. We train a conditional Real-valued Non-Volume Preserving (cRealNVP) model on expanded molecular dynamics simulations covering velocities from thermal to hypersonic speeds, incorporating a detailed balance loss term. The resulting model demonstrates improved accuracy compared to previous approaches even in the original high-velocity regime, while successfully capturing thermal-velocity scattering. Quantitative assessment shows that thermalization is approximated within acceptable tolerances. This framework provides essential capabilities for accurate ABEP intake optimization and VLEO mission planning while offering a general methodology applicable to broader rarefied gas dynamics problems requiring thermodynamic consistency.
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Extreme flows: where physics meets mathematically rigorous bounds
Bartosz Protas
https://arxiv.org/abs/2608.04859 https://arxiv.org/pdf/2608.04859

Quitobaquito Springs in south-west Arizona has been called a biological wonderland with few equals.
The springs are an oasis in the vast Sonoran desert along the US-Mexico border, held sacred by the O’odham people, who call it A’al Vaipia.
Here, water flows out of an aquifer at the bottom of a hill, runs along a short concrete channel and collects in a pond.
The pond is home to Sonoyta pupfish, which are small and silvery, with upturned jaws.
In the channel are found …

‘Total chaos’: the biological wonderland threatened by Trump’s border wall
Environmental groups are sounding the alarm over plans that threaten a desert spring that’s home to rare fish and turtles and sacred to the O’odham people

🇺🇦 #NowPlaying on KEXP's #AfternoonShow
Nubiyan Twist feat. eniola:
🎵 Body Flows
#NubiyanTwist #eniola
https://nubiyantwist.bandcamp.com/track/body-flows-feat-eniola
https://open.spotify.com/track/7v3bzT1NvVEnqEIKpkeOoK

#PhDCongratulations!!! 🥳🥳🥳Neelanchal Joshi of the #IMPRS #SolarSystemSchool successfully defended his thesis “Measuring multiscale solar flows using local correlation t…

Since it was relevant to a discussion I just had on here and is something most people probably haven't thought about much (unless you've taken one of a handful of philosophy classes), I thought I'd try to lay out a key piece of Descartes' Meditations (#philosophy

Australian innovation for the 🇬🇧 UK consumer energy market: E.ON Next combines 🇦🇺 Amber’s smart energy optimisation with half-hourly pricing
https://www.eonnext.com/tariffs/next-optimise/

Weekly Climate Solutions Digest #32!! 💖🌊✨
https://www.forpeopleandpla.net/weekly-climate-solutions-digest-32/?utm_source=bri-mastodon&utm_medium=social&src=mstdn

Weekly Climate Solutions Digest
Welcome This week, the stories share a theme: coordination at scale and giving old systems new work. Across continents, we bank energy, pool flexibility, and clean up the flows of goods and carbon. The arc is steady & practical: take what we have, connect it, and make it serve a cleaner

A discrete Boltzmann model with state-dependent power-law relaxation time for nonequilibrium transport in compressible flows
Demei Li, Zhongyi He, Huilin Lai, Yanbiao Gan, Hailong Liu, Pengfei Lin
https://arxiv.org/abs/2605.18216 https://arxiv.org/pdf/2605.18216 https://arxiv.org/html/2605.18216
arXiv:2605.18216v1 Announce Type: new
Abstract: Thermodynamic nonequilibrium effects play a central role in momentum and energy transport in compressible flows. In conventional BGK kinetic models, the relaxation time $\tau$ is taken as a constant, which neglects the dependence of the relaxation process on local macroscopic states. To overcome this limitation, we develop a discrete Boltzmann model with a density- and temperature-dependent power-law relaxation time, termed DTRT-DBM, in which $\tau=\tau_0(\rho/\rho_0)^a(T/T_0)^b$. This formulation extends the discrete Boltzmann framework to flows with spatially varying nonequilibrium intensity. The model is validated by the Sod shock tube and by analytical solutions for viscous stress and heat flux, demonstrating accurate recovery of both macroscopic wave structures and nonequilibrium quantities across shock waves, rarefaction waves, and contact discontinuities. On this basis, phase diagrams of viscous stress and heat flux are constructed to examine how these quantities depend on the power-law exponents $a$ and $b$. The extrema of these quantities depend exponentially on the model parameters and exhibit regime-dependent behaviour. The roles of $a$ and $b$ are not symmetric: the nonequilibrium response is more sensitive to $a$ when density gradients dominate, but more sensitive to $b$ when temperature gradients dominate. Within the parameter range and flow configurations examined here, higher-order viscous stress increases the growth rate of the total viscous-stress extremum, whereas higher-order heat flux reduces the growth rate of the total heat-flux extremum. These results show that the proposed model can capture different higher-order nonequilibrium responses in compressible flows and provides a framework for the modelling and analysis of multiscale nonequilibrium processes.
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Replaced article(s) found for math.DS. https://arxiv.org/list/math.DS/new
[2/2]:
- Generic-case complexity of Whitehead's algorithm, revisited
Ilya Kapovich
https://arxiv.org/abs/1903.07040
- Exponential mixing for the randomly forced NLS equation
Yuxuan Chen, Shengquan Xiang, Zhifei Zhang, Jia-Cheng Zhao
https://arxiv.org/abs/2506.10318 https://mastoxiv.page/@arXiv_mathAP_bot/114675099940694476
- Machine-Precision Prediction of Low-Dimensional Chaotic Systems from Noise-Free Data
Christof Sch\"otz, Niklas Boers
https://arxiv.org/abs/2507.09652
- Limit theorems for inhomogeneous $\phi$-mixing Markov chains
Yeor Hafouta, Brenden Williams
https://arxiv.org/abs/2510.15323 https://mastoxiv.page/@arXiv_mathPR_bot/115405447591487390
- A kernel method for the learning of Wasserstein geometric flows
Jianyu Hu, Juan-Pablo Ortega, Daiying Yin
https://arxiv.org/abs/2511.06655 https://mastoxiv.page/@arXiv_mathNA_bot/115530572827554967
- Null-Validated Topological Signatures of Financial Market Dynamics
Samuel W. Akingbade
https://arxiv.org/abs/2602.00383 https://mastoxiv.page/@arXiv_qfinST_bot/116006072151481289
- Simple generators of rational function fields
Alexander Demin, Gleb Pogudin
https://arxiv.org/abs/2602.10878 https://mastoxiv.page/@arXiv_csSC_bot/116056681962763734
- Martin Boundary and Invariant Fields of Multiplicative SHE
Hongyi Chen
https://arxiv.org/abs/2602.16126 https://mastoxiv.page/@arXiv_mathPR_bot/116096386900973756
- Counting the number of $1_{m}$-preperiodic $\mathcal{O}_{K}$-points of a discrete dynamical syste...
Brian Kintu
https://arxiv.org/abs/2606.14468 https://mastoxiv.page/@arXiv_mathNT_bot/116753018953819097
- Shadowing and Hyperbolicity for Endomorphisms of Locally Compact Groups
Dekui Peng
https://arxiv.org/abs/2606.27647 https://mastoxiv.page/@arXiv_mathGR_bot/116832321784455128
- Uniform $L^{\infty}$-Boundedness of Global Attractors for Reaction-Diffusion Equations with Neuma...
Antonio L. Pereira
https://arxiv.org/abs/2607.08061 https://mastoxiv.page/@arXiv_mathAP_bot/116894588437564813
- Stability of closed characteristics and invariant sets on star-shaped hypersurfaces
Huagui Duan, Zihao Qi
https://arxiv.org/abs/2607.15546 https://mastoxiv.page/@arXiv_mathSG_bot/116951161229689295
- Vakonomic Fluids
Ritoban Roy-Chowdhury, Mohammad Sina Nabizadeh, Oliver Gross, Anthony Gruber, Albert Chern
https://arxiv.org/abs/2607.18312 https://mastoxiv.page/@arXiv_mathph_bot/116962502170736360
toXiv_bot_toot

At an Arkansas school, a boy was hit by the school’s founder and attacked by classmates in a group session the founder led, prompting a complaint and her arrest.
State Money Still Flows: Despite a jail term for the school’s founder, "The Delta Institute for the Developing Brain" continues to operate and Arkansas still sends it public funds.
Unregulated and Growing: BY DESIGN, private schools get little oversight in Arkansas even as new opportunities to receive state m…

This Private School Had Students Scrub Floors and Attack a Fellow Classmate. The State Still Funds It.
One of the few requirements for Arkansas private schools is that they have an American flag and a flagpole. But millions in state funds go to the largely unmonitored schools while complaints about safety and fraud have gone unanswered, parents say.

Trump's court win reignites fight to sink €1.7T data deal with Europe (Politico)
https://www.politico.eu/article/european-regulators-assessing-whether-scotus-ruling-threatens-transatlantic-data-flows/
http://www.memeorandum.com/260701/p42#a260701p42

Mapping the Turn: An Eulerian Binormal-Axis Diagnostic for Recirculating 3D Flows
John Marshall Cooper, Wen Wu
https://arxiv.org/abs/2605.18439 https://arxiv.org/pdf/2605.18439 https://arxiv.org/html/2605.18439
arXiv:2605.18439v1 Announce Type: new
Abstract: Three-dimensional (3D) recirculating flows are often interpreted qualitatively from selected streamline visualizations. In separated flows, such recirculating motion is central to the drag modulation, but the local orientation of recirculation remains difficult to quantify in a field-based form. This work introduces an Eulerian binormal-axis diagnostic that locally evaluates the orientation of streamline turning at each point in the velocity field, yielding a spatially resolved field of the recirculating direction. Motivated by the Frenet-Serret binormal direction of a curved streamline, the diagnostic uses the velocity vector and its convective acceleration to extract the local streamline-turning axis without requiring explicit streamline integration. The resulting direction is encoded with barycentric RGB weights to visualize streamwise, spanwise, and wall-normal turning axis contributions. The diagnostic is first applied to Hill's spherical vortex, which provides a controlled analytic example of 3D recirculating motion for interpreting the binormal-axis direction and the associated barycentric RGB encoding. It is then applied to the mean field of a pressure-gradient-induced 3D separation bubble. The resulting visualizations show that the diagnostic reveals orientation changes that are not apparent from streamline visualization. The proposed diagnostic therefore converts qualitative streamline impressions into a spatially resolved measure of local streamline-turning orientation, providing a quantitative complement to conventional 3D flow visualization.
toXiv_bot_toot

"UK rivers face rising risk of climate 'whiplash'"
#UK #UnitedKingdom #Climate #ClimateChange

UK rivers face rising risk of climate 'whiplash'
Climate change could push UK rivers to dangerous extremes and bring more frequent rapid swings between wet and dry conditions—a phenomenon known as hydroclimatic whiplash—according to research led by the University of East Anglia (UEA). Researchers analyzed almost 700 river catchments across the UK to project how river flows may change at 2° C and 4° C of global warming. The results reveal stark regional contrasts and growing challenges for communities and water managers trying to plan fo…

🇺🇦 #NowPlaying on BBCRadio3's #NightTracks
Dobrinka Tabakova, Roman Mints, Raimondas Sviackevičius & Donatas Bagurskas:
🎵 Frozen River Flows
#DobrinkaTabakova #RomanMints #RaimondasSviackevičius #DonatasBagurskas

Replaced article(s) found for nlin.CD. https://arxiv.org/list/nlin.CD/new
[1/1]:
- A Mathematical Framework for Linear Response Theory for Nonautonomous Systems
Stefano Galatolo, Valerio Lucarini
https://arxiv.org/abs/2603.19509 https://mastoxiv.page/@arXiv_mathDS_bot/116277396967537630
- Lagrangian Ellipsoid Diagnostics in Rough Two-Dimensional Synthetic Flows: Aspect-Ratio Saturatio...
Michael Chertkov
https://arxiv.org/abs/2605.27606 https://mastoxiv.page/@arXiv_physicsfludyn_bot/116651135705771524
- Universal self-similar evolution of two-dimensional acoustic turbulence in Bose-Einstein condensates
Guillaume Costa, Sergey Nazarenko, Giorgio Krstulovic
https://arxiv.org/abs/2607.06062 https://mastoxiv.page/@arXiv_condmatquantgas_bot/116883253087715770
toXiv_bot_toot

Sidewall effects on the onset of interfacial Holmboe waves in stratified exchange flows at high Schmidt number
Guilherme Siqueira de Aquino, Metten M. de Lange, Adrien Lefauve, Matias Duran-Matute
https://arxiv.org/abs/2607.19565 https://arxiv.org/pdf/2607.19565 https://arxiv.org/html/2607.19565
arXiv:2607.19565v1 Announce Type: new
Abstract: Predicting the onset of interfacial instabilities is central to understanding turbulent mixing in natural and engineered stratified shear flows. Here, we study the onset of travelling Holmboe waves in confined exchange flows along a slope. Earlier stratified inclined duct experiments have mapped this transition, and stability analyses based on measured or prescribed profiles have explained their emergence. However, a predictive criterion linking forcing, geometry, base flow, and wave onset was still lacking. We closed this gap with a long-duct, sharp-interface asymptotic theory for the three-dimensional laminar exchange flow, including the effects of sidewall friction. The resulting analytical solution naturally identifies a confinement-adjusted Froude number, $Fr^*$, which unifies the effects of forcing and confinement into a single measure of the effective laminar exchange flow. Using this solution to parameterise sidewall drag in a practical width-averaged model, we perform linear stability analyses and numerical simulations at high Schmidt number. Together, linear stability analysis, direct numerical simulations, and existing experiments across a range of duct widths show that wave onset is accurately predicted by an approximately constant critical value of $Fr^*$. Deviations arise only in very narrow ducts, where sidewalls influence instability not only by modifying the laminar exchange flow but also by directly damping perturbations and delaying wave onset. These findings provide a predictive criterion for wave onset, reconcile long-standing discrepancies among experimental configurations, and establish lateral confinement as a fundamental control on the transition from laminar exchange to wave-driven mixing in stratified shear flows.
toXiv_bot_toot

🇺🇦 #NowPlaying on KEXP's #AfternoonShow
Nubiyan Twist feat. eniola:
🎵 Body Flows
#NubiyanTwist #eniola
https://open.spotify.com/track/7v3bzT1NvVEnqEIKpkeOoK

Electrolyte flows under magnetic fields: Manning-like counterion condensation in one dimension
Yoav Tsori, Hannes Uecker
https://arxiv.org/abs/2605.18076 https://arxiv.org/pdf/2605.18076 https://arxiv.org/html/2605.18076
arXiv:2605.18076v1 Announce Type: new
Abstract: We present a theoretical framework for unidirectional electromagnetohydrodynamic flow of dilute electrolytes under perpendicular magnetic fields. Starting from the Navier--Stokes equation coupled with the Poisson--Nernst--Planck formulation, we show that the problem admits a sequential decoupling: the Stokes equation is solved first to obtain the velocity profile, which defines a hydrodynamic potential entering the Nernst--Planck description of ions. This Lorentz-force-induced potential competes with electrostatic attraction and significantly alters ionic distributions. We analyze this mechanism in two canonical geometries. In planar Couette shear, it produces a Manning--Oosawa-like condensation transition in one dimension, a phenomenon absent in classical electrostatics. We derive an eigenvalue equation predicting a sharp threshold between counterion enrichment and depletion at the charged wall. In cylindrical Taylor--Couette flow, the same effect shifts the classical Manning criterion by a magnetic parameter, enabling tunable control of condensation. These findings extend Manning--Oosawa phenomenology to driven, non-equilibrium systems and provide a basis for magnetic manipulation of screening in electrolytes, with implications for microfluidics, electrochemical systems, and nonlinear boundary-value theory.
toXiv_bot_toot

Discrete Boltzmann model at Burnett level for compressible multicomponent flows under external forces
Demei Li, Huilin Lai, Chuandong Lin, Suni Chen
https://arxiv.org/abs/2607.20029 https://arxiv.org/pdf/2607.20029 https://arxiv.org/html/2607.20029
arXiv:2607.20029v1 Announce Type: new
Abstract: This work extends the Burnett-level discrete Boltzmann model (DBM) from single-component to multicomponent compressible flows under external forces, building on the fundamental framework of the high-precision discrete kinetic method. A high-isotropy 25-discrete-velocity set is adopted to guarantee numerical stability and spatial symmetry, while a rigorous moment-matching strategy is developed to construct the equilibrium distribution function and external force term. Different from the single-component counterpart, the present model intrinsically incorporates interspecies mass diffusion effects and multi-component thermodynamic nonequilibrium behaviors, which are critical for complex compressible multicomponent systems. The Chapman--Enskog expansion verifies that the proposed model can exactly recover the Burnett-level governing equations for forced multicomponent compressible flows in the continuum limit. Five canonical benchmark cases, including multicomponent mass diffusion, compressible Sod shock tube, thermal Couette flow, Kelvin--Helmholtz instability, and Rayleigh--Taylor instability, are systematically performed. Numerical results demonstrate that the developed Burnett-level multicomponent DBM achieves high accuracy and robustness in capturing both hydrodynamic evolution and multicomponent nonequilibrium characteristics under external forces.
toXiv_bot_toot

Self-focusing of helicity drives finite-time singularities in inviscid flows
Mokhtar Adda-Bedia, Sergio Rica
https://arxiv.org/abs/2605.17569 https://arxiv.org/pdf/2605.17569 https://arxiv.org/html/2605.17569
arXiv:2605.17569v1 Announce Type: new
Abstract: This paper deals with the longstanding quest of the possible existence of finite-time singularities in the equations governing the dynamics of inviscid fluids, namely, Euler equations. Here, two contributions are brought for the case of perfect fluids with finite initial energy. First, a self-similar velocity field inspired by Leray Ansatz is proposed which allows for a separation of variables that transforms the original partial differential Euler equations to a nonlinear system of ordinary differential equations. This system can be solved semi-analytically and allows a continuum set of solutions parametrised by a self-similar exponent, $\nu$. Second, we use the conservation laws of Euler equations to select the possible finite-time singular solutions and the related self-similar exponents. We find that the helicity is the driving mechanism of the blow-up through a self-focusing mechanism. The flow near the singularity separates into two phases. A first phase is within a tubular region that shrinks as a power-law $(t_c-t)^\nu$, with $t_c$ the blow-up time, where the helicity is focused. This region is separated by a sharp interface from an outer region where the vorticity, and thus helicity, is identically zero. We found that the finite-time singularity may be either point-like or line-like depending on the dynamics of the tubular region along its axis of symmetry. Incidentally for a point-like singularity we recover the Leray scaling $\nu=1/2$ paving the way to a generalisation of this approach for the Navier-Stokes equations. Finally, we conjecture that if the helicity vanishes initially, no finite-time singularity would be possible, since in this case the singularity occurs at infinite time from the initial condition.
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Cavitation Acoustic Perturbation Equations: A Computational Framework for Source-Resolved Multiphase Hydroacoustics
Zhi Cheng, Rajeev K. Jaiman
https://arxiv.org/abs/2607.19567 https://arxiv.org/pdf/2607.19567 https://arxiv.org/html/2607.19567
arXiv:2607.19567v1 Announce Type: new
Abstract: This work develops a cavitation-consistent acoustic perturbation framework for predicting sound generation and propagation in cavitating flows. Unlike conventional acoustic perturbation equations for single-phase or weakly compressible flows, the proposed formulation embeds cavitation physics directly into the acoustic equations. The cavitation acoustic perturbation equations (CAPE) incorporate vapor mass transfer, mixture compressibility, and pressure-rate effects within a unified formulation, allowing cavitation-induced noise sources to be resolved in the computational domain. The numerical framework is verified using one-dimensional wave-propagation problems. The solutions become insensitive to further mesh and time-step refinement, the perfectly matched layer suppresses boundary reflections, and the predicted attenuation over a range of source frequencies follows Stokes' sound attenuation law. The framework is then applied to cavitating flow past a circular cylinder and a NACA hydrofoil. The non-cavitating benchmark shows dipole-like radiation associated with unsteady loading, whereas cavitating cases exhibit monopole-like or geometry-modulated radiation caused by volumetric phase change. Source-term analyses identify tonal frequencies associated with vortex shedding, cavity shedding, and collapse-induced excitation. The phase-change terms provide a direct volumetric contribution to the monopole-like source, while localized collapse events appear through amplification of the pressure-rate source. The proposed framework extends acoustic perturbation methods to cavitating multiphase flows and provides an efficient tool for hydroacoustic prediction, source localization, and mechanism analysis in marine and hydraulic applications.
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Replaced article(s) found for physics.flu-dyn. https://arxiv.org/list/physics.flu-dyn/new
[1/1]:
- Mixing Fronts in Smooth Chaotic Flows
Heyman Joris, Le Borgne Tanguy, Lester Daniel
https://arxiv.org/abs/2506.15255 https://mastoxiv.page/@arXiv_physicsfludyn_bot/114709421274451465
- Real-time reinforcement learning for turbulent state-dependent control in a bluff-body wake
Junjie Zhang, Chengwei Xia, Xianyang Jiang, Isabella Fumarola, Georgios Rigas
https://arxiv.org/abs/2509.11002 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115213145016358332
- Toward a unified data-driven turbulence model through multi-objective learning
Zhuoran Liu, Haochen Wang, Zhuolin Zhao, Heng Xiao
https://arxiv.org/abs/2509.17189 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115252943951151336
- Localization of sources in weakly nonlinear fluid systems using linear and quadratic sensitivity ...
Qi Wang, Zejian You
https://arxiv.org/abs/2601.06304 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115887064467176458
- Structures of elastoinertial turbulence in pipe flow
Manish Kumar, Michael D. Graham
https://arxiv.org/abs/2601.15637 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115943599169371363
- Revisiting the Frictional Control of the Antarctic Circumpolar Current From the Energy Diagram
Takuro Matsuta, Yuki Tanaka, Atsushi Kubokawa
https://arxiv.org/abs/2602.23742 https://mastoxiv.page/@arXiv_physicsfludyn_bot/116158781888135470
- Fluid dynamics as intersection problem
Nikita Nekrasov, Paul Wiegmann
https://arxiv.org/abs/2512.25053 https://mastoxiv.page/@arXiv_hepth_bot/115819554836846738
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Spatio-Temporal Signatures of Intermittency in Helically Rotating Turbulence through Topological Data Analysis
Snigdhashree Mallick (International Institute of Information Technology, Bangalore, India), Yashwanth Ramamurthi (International Institute of Information Technology, Bangalore, India), Shiva Kumar Malapaka (International Institute of Information Technology, Bangalore, India), Amit Chattopadhyay (International Institute of Information Technology, Bangalore, India)
https://arxiv.org/abs/2605.17560 https://arxiv.org/pdf/2605.17560 https://arxiv.org/html/2605.17560
arXiv:2605.17560v1 Announce Type: new
Abstract: A central challenge in hydrodynamic turbulence is identifying precisely when, and at which length scales, strong turbulent fluctuations (STFs) emerge and develop into intermittent events, which are often obscured by conventional statistical diagnostics. We address this problem by applying a Topological Data Analysis (TDA) framework to reveal the spatiotemporal signatures of intermittency in low-resolution ($128^3$) helically rotating turbulent flows. Vorticity magnitude and length-scale (eddy size) fields are used as scalar observables for TDA: vorticity characterizes rotational dynamics that generate multiscale flow structures, while length-scale fields encode the scales at which intermittent activity arises. Their evolving topology is quantified using persistence diagrams and Wasserstein-distance metrics. Compared with traditional statistical approaches, this framework is more sensitive to localized and short-lived flow variations, enabling clearer detection of intermittent behavior. Pronounced variations in Wasserstein-distance heatmaps provide direct signatures of STFs across space and time. Together, these results demonstrate that TDA offers an effective complementary tool for detecting STFs that lead to intermittency within turbulent regime.
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High-Order ADER-DG Hydrodynamics with ExaHyPE: Implementation, Validation, and Astrophysical Benchmarking
Andr\'es Mauricio Su\'arez Mantilla, Leonardo Casta\~neda Colorado
https://arxiv.org/abs/2605.17132 https://arxiv.org/pdf/2605.17132 https://arxiv.org/html/2605.17132
arXiv:2605.17132v1 Announce Type: new
Abstract: We describe a high-order ADER-DG solver for the compressible Euler equations within the ExaHyPE framework. The implementation combines a high-order ADER-DG polynomial representation, a local space-time DG predictor, adaptive mesh refinement, and an a posteriori subcell finite-volume limiter. We test the code on a deliberately mixed set of one- and two-dimensional problems: a strong-shock Sod-type problem, the Shu-Osher shock-entropy interaction, the Woodward-Colella blast wave, a contact-driven vortex sheet, and a shock-interface interaction. The one-dimensional cases recover the expected Euler wave patterns and show clear order-dependent gains in smooth and oscillatory regions. The two-dimensional cases probe a different part of the method, namely contact preservation, shear-driven roll-up, baroclinic vorticity deposition, and Richtmyer-Meshkov-type growth. In these tests the high-order update gives the expected resolution away from discontinuities, whereas the subcell limiter keeps the calculation stable near shocks and steep interfaces. The resulting code provides a reproducible ExaHyPE implementation for idealised inviscid, non-relativistic flows in which shocks, contacts, and multidimensional interfaces are the dominant features.
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Replaced article(s) found for physics.flu-dyn. https://arxiv.org/list/physics.flu-dyn/new
[1/1]:
- On the stability of an in-line formation of hydrodynamically interacting flapping plates
Monika Nitsche, Anand U. Oza, Michael Siegel
https://arxiv.org/abs/2410.04626 https://mastoxiv.page/@arXiv_physicsfludyn_bot/113270998236203403
- Side-wall wetting and linear stability of falling films
Hammam Mohamed, J\"orn Sesterhenn
https://arxiv.org/abs/2504.13300 https://mastoxiv.page/@arXiv_physicsfludyn_bot/114374794050144417
- An Omni-Temporal Theory for Hydrodynamic Dispersion and Reaction in Porous Media
Md Abdul Hamid, Kyle C. Smith
https://arxiv.org/abs/2505.06063 https://mastoxiv.page/@arXiv_physicsfludyn_bot/114493702701690116
- Confirming Wave Turbulence Predictions in Rotating Turbulence
Omri Shaltiel, Omri Gat, Eran Sharon
https://arxiv.org/abs/2510.25446 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115462467154250733
- Using Physics Informed Neural Network (PINN) and Neural Network (NN) to Improve a $k-\omega$ Turb...
Lars Davidson
https://arxiv.org/abs/2511.12493 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115570134553603649
- Oscillating Detonation of Liquid Ammonia
Wenhao Wang, Zongmin Hu, Peng Zhang
https://arxiv.org/abs/2511.14167 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115575358542454196
- On the Poisson-Source Basis of Logarithmic Wall-Pressure-Variance Growth
Jonathan M. O. Massey, Joseph C. Klewicki, Beverley J. McKeon
https://arxiv.org/abs/2511.16776 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115603689363840109
- Convolutional causal learning for aerodynamic flows
Ryo Koshikawa, Ryo Araki, Qiong Liu, Kai Fukami
https://arxiv.org/abs/2601.19104 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115971839485449464
- Assessing engineering wake models against operational data: insights from the Lillgrund wind farm...
Siguenza-Alvarado, Harrison, Mohammadi, Vishwakarma, Bossanyi, Landberg, Bastankhah
https://arxiv.org/abs/2601.21035 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115983015393462612
- Neural equilibria for long-term prediction of nonlinear conservation laws
Benitez, Hegazy, Guo, Dokmani\'c, Mahoney, de Hoop
https://arxiv.org/abs/2501.06933 https://mastoxiv.page/@arXiv_csLG_bot/113825452743912532
- Self-similar rupture of thin films of power-law fluid
Michael C Dallaston, Steven A Kedda, Scott W McCue
https://arxiv.org/abs/2509.05383 https://mastoxiv.page/@arXiv_condmatsoft_bot/115173629129170202
- Instability and self-propulsion of flexible autophoretic filaments
Ursy Makanga, Akhil Varma, Panayiota Katsamba
https://arxiv.org/abs/2509.10153 https://mastoxiv.page/@arXiv_condmatsoft_bot/115207443699020835
- Analytical response functions for a compressible thin fluid layer with odd viscosity
Abdallah Daddi-Moussa-Ider, Yuto Hosaka, Shigeyuki Komura
https://arxiv.org/abs/2602.18136 https://mastoxiv.page/@arXiv_condmatsoft_bot/116119064615788127
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Information Transport and Observability in Compressible Aerodynamics
Bo Zhang
https://arxiv.org/abs/2607.20177 https://arxiv.org/pdf/2607.20177 https://arxiv.org/html/2607.20177
arXiv:2607.20177v1 Announce Type: new
Abstract: Pressure measurements provide sparse but direct observations of compressible aerodynamic flows, yet how information about hidden aerodynamic parameters is transported through the flow and encoded in these observations remains poorly understood. Here, we investigate information transport and observability in compressible aerodynamics using a differentiable shock-capturing immersed-boundary solver. By propagating gradients through the full unsteady flow solution, an automatic-differentiation-based observability metric is introduced to quantify the sensitivity of sparse pressure measurements to unknown aerodynamic parameters and identify informative sensing locations for inverse learning. The results reveal that aerodynamic information is transported non-uniformly through the flow field, producing localized regions of high observability. Inverse-learning experiments further demonstrate that observability and learnability are related but distinct concepts: although highly observable probes generally facilitate accurate parameter recovery, the highest-observability probe is not consistently the most effective for parameter inference. Furthermore, both the flow regime and the airfoil geometry substantially influence the distribution of observability and the convergence behavior of inverse learning. These findings establish a quantitative framework for understanding how aerodynamic information is encoded in sparse measurements and demonstrate the potential of automatic differentiation for observability analysis, informative sensor selection, and aerodynamic inverse analysis.
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A formal log(Re)-cost framework for the engineering turbulence problem
Jiaqi Li, Robert F. Kunz, George Huang, Xiang I. A. Yang
https://arxiv.org/abs/2607.20199 https://arxiv.org/pdf/2607.20199 https://arxiv.org/html/2607.20199
arXiv:2607.20199v1 Announce Type: new
Abstract: In fluid engineering, the turbulence problem is the longstanding challenge of obtaining accurate predictions of engineering quantities at affordable computational cost. Viewed through computational complexity, a practical algorithm requires cost growth no worse than $O(N)$, where $N$ denotes problem size. For turbulent flows, the problem size may be approximated by the number of dynamically relevant scales and hence by the Reynolds number $Re$. We propose a multi-fidelity, physics-constrained, data-driven framework designed to meet this criterion under stated assumptions. We augment the Spalart--Allmaras model through field inversion and machine learning using a constrained formulation that preserves the law of the wall. The model is trained at a low Reynolds number, where high-fidelity data are affordable, and deployed at higher Reynolds numbers. For a mean-flow-aligned grid in a wall-bounded flow, fixed spanwise resolution, and steady-solver cost linear in grid-point count, the low-fidelity RANS prediction scales as $O(\log(Re))$. The high-fidelity calculation and learning stage each contribute $O(Re^0)$ relative to the target Reynolds number, giving an overall formal cost of $O(\log(Re))$. In plane channel flow, a model trained at $Re_\tau=1000$ corrects the wake-layer error of the baseline model and retains the improvement at $Re_\tau=5200$. In the periodic hill, a model trained at $Re_b=5600$ is tested at $Re_b=10595$, $19000$, and $37000$. The constrained formulation preserves separation and recovery behavior as Reynolds number increases, yields the lowest root-mean-square error across all tests, and exhibits nearly Reynolds-number-independent error, indicating robust extrapolation.
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Replaced article(s) found for physics.flu-dyn. https://arxiv.org/list/physics.flu-dyn/new
[1/1]:
- Exact results for dissipation and steady creeping flow in three-dimensional chiral active fluids
Laura Meissner-Oszer, Bogdan Cichocki, Jeffrey C. Everts
https://arxiv.org/abs/2510.19658 https://mastoxiv.page/@arXiv_physicsfludyn_bot/115422802755500601
- Pressure beneath a periodic travelling water-wave in constant-vorticity flow over a flat bed
Adrian Constantin, Nicolas Gindrier, Otmar Scherzer
https://arxiv.org/abs/2602.21077 https://mastoxiv.page/@arXiv_physicsfludyn_bot/116130402894456942
- A minimal wake-vortex model explains formation flight of flapping birds
Olivia Pomerenk, Kenneth S. Breuer
https://arxiv.org/abs/2602.22043 https://mastoxiv.page/@arXiv_physicsfludyn_bot/116136202119473646
- Lagrangian Ellipsoid Diagnostics in Rough Two-Dimensional Synthetic Flows: Aspect-Ratio Saturatio...
Michael Chertkov
https://arxiv.org/abs/2605.27606 https://mastoxiv.page/@arXiv_physicsfludyn_bot/116651135705771524
- On the Theory of Bulk Viscosity of Cold Plasmas and Thermodynamics of Alkali-Noble Gas Cocktails
Albert M. Varonov, Todor M. Mishonov
https://arxiv.org/abs/2511.14790 https://mastoxiv.page/@arXiv_physicsplasmph_bot/115581169803088580
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