Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2401.17071

Influence of the Reynolds number from $Re_τ= 150$ to $210$ on size-dependent bipolar charging

Simon Jantač·Holger Grosshans
View original source ↗Read source document ↗Export metadata ↓

Abstract

We recently found wall-bounded turbulence to suppress and control bipolar triboelectric charging of particles of identical material. This control is due to fluid modifying the motion of light particles. Thus, the particles' charge distribution depends on their Stokes number distribution. More specifically, fluid forces narrow the bandwidth of the charge distribution, and bipolar charging reduces dramatically. Consequently, not the smallest but mid-sized particles collect the most negative charge. However, the influence of the Reynolds number or particle concentration on bipolar charging of polydisperse particles is unknown. This paper presents the charging simulations of same-material particles the in different wall-bounded flows. In a comprehensive study, we vary the Reynolds number from $Re_τ=$ $150$ to $210$ and the particle number density from $4 \times 10^9 \ \mathrm{m}^{-3}$ to $1 \times 10^{10} \ \mathrm{m}^{-3}$ to further explore the influence of the carrier flow on bipolar charging. We model charge transfer based on the balance of transferable charge species. Such species can represent adsorbed ions transferred during collisions or free electrons captured into a lower energy state on the other surface. The turbulent flow is modeled via Direct Numerical Simulations (DNS) and is coupled to the particulate phase modeled via the Discrete Element Method (DEM). Overall, our multiphysics approach couples the fluid dynamics, electric field, triboelectric charging, and particle momentum into one complex simulation.

Explore related subjects

physics.flu-dyncond-mat.soft

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Simon Jantač, Holger Grosshans. 2024-01-30. Influence of the Reynolds number from $Re_τ= 150$ to $210$ on size-dependent bipolar charging. https://doi.org/10.1088/1742-6596%2F2702%2F1%2F012027

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Reynolds-number regimes of corrugation-induced lift enhancement in two-dimensional dragonfly-like wings

Corrugated wing structures commonly observed in insect wings can enhance aerodynamic performance at low Reynolds numbers ($Re \simeq O(10^3)$). However, their effectiveness strongly depends on the Reynolds number, and the corresponding operating range remains unclear. Direct numerical simulations of an impulsively started corrugated wing are performed over a wide range of Reynolds numbers ($100 \leq Re \leq 4000$) to identify the conditions under which corrugation is beneficial. Three Reynolds-number regimes are identified within the examined parameter sets. No characteristic lift-enhancement mechanism is observed for $100 \leq Re < 1000$. For $1000 \leq Re \leq 4000$, lift enhancement is associated with alternating vortices formed within the V-shaped region of the corrugated wing, which generate low-pressure regions near the wing surface. Above $Re=2000$, the collapse and confinement of a secondary vortex within the V-shaped region emerge as an additional dominant mechanism, further enhancing the lift. An analysis based on a local Reynolds number organizes the onset conditions of these mechanisms and provides a useful local measure for characterizing the onset of vortex detachment from the corrugation. Furthermore, long-time simulations confirm that the observed vortex dynamics persist well beyond the initial transient response following an impulsive start. These results elucidate Reynolds-number-dependent lift-enhancement mechanisms and define aerodynamic conditions under which corrugated wings provide an advantage.

physics.flu-dyn↗
arXiv2026

PhysMiner: An Agentic AI Framework for Automated Flow Component Analysis

Uncovering the physical mechanisms of turbulent flows remains a fundamental challenge in fluid mechanics. In particular, conventional velocity-gradient analysis methods suffer from shear contamination, which hinders accurate identification of the dominant physical mechanisms. This study presents PhysMiner, an automated framework integrating the triple decomposition method of the velocity gradient tensor with large language model-driven reasoning for turbulence-physics discovery. The triple decomposition module automatically decomposes flow fields into rigid rotation, pure shearing, and normal straining components, enabling statistical analysis, contour visualization, vortex-line extraction, and threshold-insensitive vortex identification while eliminating shear contamination. These automated capabilities are validated across five benchmarks, ranging from canonical configurations to complex engineering flows. A discover-physics agent combines flow statistics, spatial structures, and literature-derived knowledge to perform pattern recognition and physical inference, while a review Agent iteratively validates physical consistency to ensure reliable conclusions. A continuously evolving Triple Decomposition Library accumulates statistical knowledge from successfully analyzed flows, enabling cross-case comparison and progressive enhancement of inductive capability. The complete PhysMiner pipeline is validated end-to-end on the periodic hill flow, where the framework autonomously generates turbulence modeling recommendations and derives an improved subgrid-scale model with superior Reynolds-stress predictions. PhysMiner is open to the public and establishes a foundation for long-term collaborative advancement in automated turbulence-physics discovery.

physics.flu-dyn↗
arXiv2026

Lattice Boltzmann Methods for Navier-Stokes Equations in General Orthogonal Coordinates for Efficient Flow Simulations using Nonuniform Clustered Grids

Resolving multiscale fluid flows or boundary layers effectively requires the use of nonuniform meshes with local grid clustering. The standard lattice Boltzmann method (LBM), a kinetic theory-based approach for computational fluid dynamics, however, is restricted to the use of uniform Cartesian grids. We present new and improved formulations of the LBM that accommodate continuously varying spatial grids via coordinate transformations to simulate the Navier-Stokes equations (NSE) in the general orthogonal coordinates (GOC). They are constructed using a Chapman-Enskog analysis to specify the equilibrium moments of the distribution functions and the geometric force terms used in the collision step to be dependent on the local metric factors and their spatial derivatives, along with the density, momentum and their fluxes, and some correction terms related to the normal velocity gradients so as to accurately represent the NSE in the GOC. The resulting GOC-LBM importantly maintains the simplicity of the collide-and-stream approach and is Galilean invariant that is free of the cubic velocity artifacts. Our GOC-LBM is general and modular in that it can be used with any collision model with appropriate modifications to the equilibria and forcing terms. We present its implementation details for a variety of collision models while the central moments-based model using multiple relaxation times was found to be the most robust in practical implementations. We validate the GOC-LBM through numerical simulations for various benchmark flow problems. Moreover, we demonstrate significant computational advantages of our approach for a case study on simulating boundary layer flows efficiently that involves coupling the GOC-LBM for the NSE with a new GOC-LB scheme for solving the magnetic induction equation for magnetohydrodynamics (MHD), and for another case study involving orthogonal curvilinear grids.

physics.flu-dyn↗