Drag Phenomena Research Articles

On the high accuracy to test dragging of inertial frames with the LARES 2 space experiment

In this paper we treat some aspects of the LARES 2 space experiment to test the general relativistic phenomenon of dragging of inertial frames, or frame-dragging, in particular we discuss some aspects of its relative accuracy which can approach one part in a thousand. We then, once again respond to the criticisms of the author of a recent paper about the accuracy in the measurement of frame-dragging with LARES 2. The claims of such a paper are not reproducible in any independent analyses. Indeed, it claims that the accuracy in the test of frame-dragging, which can be reached by the LARES 2 space experiment, is several orders of magnitude larger than previously estimated in a number of papers. Here we show that such a paper is based on a number of significant misunderstandings and conceptual mistakes. Furthermore, it is puzzling to observe that previous papers by the same author contained completely opposite statements about the accuracy which can be reached using two satellites with supplementary inclinations, such as in the LARES 2 space experiment, and in general with laser-ranged satellites.

Two-stage annealing-induced secondary grain growth for enhanced efficiency in CdTe solar cells on flexible polyimide foils

Flexible CdTe solar cells integrated onto polyimide foils are a promising renewable power generation technology. Optimizing crystal structure and reducing grain boundary recombination by CdCl2 annealing are the key approaches to increase carrier concentration and improve device performance. However, the inherent thermal constraints of polyimide substrates limit the feasibility of achieving full annealing. In response, we introduce a novel two-stage annealing process: a primary recrystallization at 350 °C followed by a secondary recrystallization at 380 °C. Employing a rigorous investigation of surface and interface energy minimization, strain energy minimization, and the growth kinetics of Cl drag phenomena, this method induces significant secondary grain growth, surpassing the film thickness itself. The culmination of these efforts yields an extraordinary power conversion efficiency (PCE) of 12.2 %, marking a historic achievement for sputtered CdTe solar cells on polyimide substrates. This study not only unveils a pioneering approach to grain boundary engineering but also offers insights into optimizing the CdCl2 annealing process for CdTe absorbers, ultimately facilitating the realization of high-efficiency, flexible CdTe solar cells.

Drag Resistivity of Hole-Hole Static Interactions with the Effect of Non- Homogeneous Dielectric Medium

BACKGROUND: We have study the Coulomb drag phenomena for hole-hole static potentials theoretically and measured numerically using the random phase approximation (RPA) method OBJECTIVE: The drag resistivity is evaluated at low temperature, large interlayer separation limit and weakly screening regime, with the geometry of two atomically thin materials, such as, BLG/GaAs based multilayer system, is a promising systems in nanomaterials and technology METHOD: Static local field corrections (LFC) are considered to take into account the Exchange-correlations (XC) and mutual interaction effects with varying concentrations of active and passive layer RESULT: It is found that the drag resistivity is found enhanced on using the LFC effects and increases on increasing the effective mass. In Fermi-Liquid regime, drag resistivity is directly proportional to T^2, n^(-3), d^(-4) and ϵ^2 with respect to temperature (T), density (n), interlayer separation (d~nm) and dielectric constant (ϵ_2), respectively. CONCLUSION: Dependency of drag resistivity is measured and compared to 2D e-e and e-h coupled-layer systems with and without the effect of non-homogeneous dielectric medium.

Drag resistivity in double-layer gapped graphene structures

We study the frictional drag phenomenon in a double-layer system made of two parallel gapped graphene layers by calculating the Coulomb drag resistivity. The random-phase approximation is employed to determine the polarizability functions of layers and the frequency-dependent dielectric function of the structure. Our computations illustrate that the Coulomb drag resistivity in double-layer gapped graphene systems show some interesting different features, compared to that in other double-layer ones. Coulomb drag resistivity in the system steadily increases as temperature increases but quickly decreases with the increase in interlayer distance. With small interlayer separations, the drag resistivity behaves as a smoothly increasing function of the bandgap. Nevertheless, with sufficiently large separations, the Coulomb drag resistivity increases with small bandgaps but decreases with larger ones. We observe that a finite bandgap has remarkable contributions to the frictional drag phenomenon, therefore it is necessary to take into account this factor in calculations to make better agreements with experimental works.

Dragging of inertial frames in the composed Kerr-Newman-orbiting-ring system

The dragging of inertial frames by an orbiting object, a well known phenomenon in general relativity, implies that the horizon angular velocity ΩHBH-ring of a central black hole in a composed black-hole-orbiting-ring system is no longer related to its angular-momentum JH by the familiar vacuum functional relation ΩH(JH)=JH/Mα (here {M,α} are respectively the mass and normalized area of the central spinning black hole). Using a continuity argument, according to which the black-hole angular velocity changes smoothly during an adiabatic assimilation process of an orbiting ring, it has recently been revealed that the composed Kerr-ring system is characterized by the universal (that is, spin-independent) relation ΔΩH≡ΩHBH-ring(JH,JR,R→RH+)−ΩHKerr(JH)=JR/4M3, where {R,JR} are respectively the radius of the ring and its orbital angular momentum and RH is the horizon radius of the central Kerr black hole. This intriguing observation naturally raises the following physically interesting question: Does the physical quantity ΔΩH in a composed black-hole-orbiting-ring system is always characterized by the near-horizon functional relation ΔΩH=JR/4M3 which is independent of the spin (angular momentum) JH of the central black hole? In order to address this important question, in the present compact paper we explore the physical phenomenon of dragging of inertial frames by an orbiting ring in the composed Kerr-Newman-black-hole-orbiting-ring system. In particular, using analytical techniques, we reveal the fact that in this composed two-body (black-hole-ring) system the quantity ΔΩH has an explicit non-trivial functional dependence on the angular momentum JH of the central spinning black hole.

Magnetized Cross tetra hybrid nanofluid passed a stenosed artery with nonuniform heat source (sink) and thermal radiation: Novel tetra hybrid Tiwari and Das nanofluid model

Researchers around the planet are attempted to explore the influence of various non-Newtonian fluids with the mono and dihybrid nanoparticles in the status of blood flowing arteries to investigate the heat transference aspect for the cure of various diseases. Current examination is created to investigate the effect of extended novel tetra hybrid Tiwari and Das nanofluid model on blood flow arteries with consideration of Cross non-Newtonian fluid model. Heat transference assessment has been taken with the insertion of impacts like heat source/sink, viscous dissipation, Joules heating as well as nonlinear thermal radiation. PDE are designed to investigate the momentum of blood flowing and temperature analysis. The governing PDE are converted into ODE with the application of similarity conversions and furthermore managed these ODE numerically with the utilization of MATLAB builtin bvp4c scheme. The obtained outcomes are studied numerically as well as graphically in the case of diverse dimensionless variables ranges between 0.5≤M≤2, 0.1≤We≤4, 0.1≤n≤1.5, 0.1≤γ≤2, 0.5≤Rd≤2, 19≤Pr≤22, 0.1≤θw≤1.5, 0.1≤Ec≤2.1, 0.5≤U≤2, 0.5≤W≤2 versus velocity, temperature, wall frictional factor and heat transition rate. From obtained outcomes it is reflected that the surface drag phenomenon weakens by the boost of a Weissenberg number and an increment variation in magneto force provides a resistance against the fluid flow. Temperature within the arteries intensifies by the advantage of a thermal radiation and viscous dissipation.

Effects of Strain-Softening and Strain-Rate Dependence on the Anchor Dragging Simulation of Clay through Large Deformation Finite Element Analysis

Large-deformation finite element (LDFE) analysis with the coupled Eulerian–Lagrangian (CEL) technique for large-deformation soil functions without twisting or distorting the mesh. However, the model does not consider the strain-softening and strain-rate dependence of clay-based soils. The undrained shear strength of clay is sensitive to the strain rate. In addition, the strain-softening effect of soil strength reduction accompanied by large-scale shear deformation should be considered. In this study, anchor dragging simulations were performed for large-deformation analysis considering strain-softening and strain-rate dependence. Furthermore, a shear strength equation expressing the strain-softening and strain-rate dependence of the Tresca constitutive model was developed based on VUMAT, an ABAQUS/Explicit subroutine. The equation was designed so that it could be linked to the LDFE/CEL model. The model was verified by performing comparative analysis with the Mohr–Coulomb (M–C) perfect-plasticity model. The newly constructed Tresca base strain-softening and strain-rate-dependence VUMAT algorithm in the LDFE/CEL model analysis confirmed the effects of strain-softening and strain-rate dependence. The proposed model enabled a highly realistic simulation of the actual phenomenon than the M–C model. Finally, a parametric study on strain-softening and strain-rate dependence was conducted, and the behavior of clay due to the anchor drag phenomenon was revealed.

Drag-induced dynamical formation of dark solitons in Bose mixture on a ring

Andreev-Bashkin drag plays a very important role in multiple areas like superfluid mixtures, superconductors and dense nuclear matter. Here, we point out that the drag phenomenon can be also important in physics of solitons, ubiquitous objects arising in a wide array of fields ranging from tsunami waves and fiber-optic communication to biological systems. So far, fruitful studies were conducted in ultracold atomic systems where nontrivial soliton dynamics occurred due to inter-component density-density interaction. In this work we show that current-current coupling between components (Andreev-Bashkin drag) can lead to a substantially different kind of effects, unsupported by density-density interactions, such as a drag-induced dark soliton generation. This also points out that soliton dynamics can be used as a tool to experimentally study the dissipationless drag effect.

Development and benchmarking of numerical model in OpenFOAM® for the prediction of channel segregation during columnar alloy solidification

• Benchmark sn-5 wt%Pb alloy solidification problem is simulated using OpenFOAM solver. • Mesh sensitivity analysis is performed to resolve the flow in channels segregates. • Effect of microsegregation and mushy zone models on channels formation is studied. • Scheil's model predicts more negative and positive segregation than Lever rule. • Inertial drag in mushy zone significantly affects the channel segregates formation. In the past, most of the numerical studies on the prediction of macrosegregation and mesosegregation (e.g. channel type segregation) were performed using in-house codes and commercial software, both of which have limitations such as huge license costs, non-availability for general public research etc. In this study, a dedicated CFD solver is developed in an open-source platform – OpenFOAM® for the prediction and characterization of channel segregates in castings. The solver accounts for the fluid flow, heat transfer, species transport, multiscale segregation, solidification and mushy zone drag phenomena that occur during alloy solidification. The developed solver is extensively validated with the reported benchmarked experimental and numerical results for the sn-Pb alloy solidification. Direct numerical simulations (DNS) are performed to resolve the flow field in and around the channels (which are of mesoscopic length scale) for the first time. It is observed that mesh size ≤ 2 d 2 (secondary dendritic arm spacing) is required to resolve the flow in channels and accurately predict their morphology and locations. Further, the effect of different microsegregation and mushy zone drag models on the segregation and morphology of channel segregates is thoroughly investigated. The predicted extent of negative and positive segregation is found to be more (negative segregation ∼ 7.7 wt%Pb and positive segregation ∼ 18.7 wt%Pb) in Scheil’s microsegregation model compared to Lever rule. Furthermore, the inertial drag in the mushy zone significantly affects the convective transport of solute and thereby the morphology and the number of channel segregates.

What’s Live Got to Do with It?

With Covid-19 closure of performance spaces, drag performers were in a unique position due to the historic relationship between queer performance and recorded media, and the history of LGBTQ2+ community building through social media. Rather than — or perhaps in addition to—constituting a moment of rupture, the sudden phenomenon of digital drag presents a vital moment for revealing the relationship among liveness, media, and citational reproduction in drag’s history.

Interband magnon drag in ferrimagnetic insulators

We propose a new drag phenomenon, an interband magnon drag, and report on interaction effects and multiband effects in magnon transport of ferrimagnetic insulators. We study a spin-Seebeck coefficient $S_{\textrm{m}}$, a magnon conductivity $\sigma_{\textrm{m}}$, and a magnon thermal conductivity $\kappa_{\textrm{m}}$ of interacting magnons for a minimal model of ferrimagnetic insulators using a $1/S$ expansion of the Holstein-Primakoff method, the linear-response theory, and a method of Green's functions. We show that the interband magnon drag enhances $\sigma_{\textrm{m}}$ and reduces $\kappa_{\textrm{m}}$, whereas its total effects on $S_{\textrm{m}}$ are small. This drag results from the interband momentum transfer induced by the magnon-magnon interactions. We also show that the higher-energy band magnons contribute to $S_{\textrm{m}}$, $\sigma_{\textrm{m}}$, and $\kappa_{\textrm{m}}$ even for temperatures smaller than the energy difference between the two bands.

Diffusive Fizeau Drag in Spatiotemporal Thermal Metamaterials.

Fizeau drag means that the speed of light can be regulated by the flow of water, owing to the momentum interaction between photons and moving media. However, the dragging of heat is intrinsically elusive, due to the absence of momentum in thermal diffusion. Here, we design a spatiotemporal thermal metamaterial based on heat transfer in porous media to demonstrate the diffusive analog to Fizeau drag. The space-related inhomogeneity and time-related advection enable the diffusive Fizeau drag effect. Thanks to the spatiotemporal coupling, different propagating speeds of temperature fields can be observed in two opposite directions, thus facilitating nonreciprocal thermal profiles. The phenomenon of diffusive Fizeau drag stands robustly even when the direction of advection is perpendicular to the propagation of temperature fields. These results could pave an unexpected way toward realizing the nonreciprocal and directional transport of mass and energy.

Rotation of the polarization of light as a tool for investigating the collisional transfer of angular momentum from rotating molecules to macroscopic gas flows

We present a detailed theoretical and experimental study of the rotation of the plane of polarization of light traveling through a gas of fast-spinning molecules. This effect is similar to the polarization drag phenomenon predicted by Fermi a century ago and it is a mechanical analog of the Faraday effect. In our experiments, molecules were spun up by an optical centrifuge and brought to the super-rotor state that retains its rotation for a relatively long time. Polarizability properties of fast-rotating molecules were analyzed considering the rotational Doppler effect and Coriolis forces. We used molecular dynamics simulations to account for intermolecular collisions. We found, both experimentally and theoretically, a nontrivial nonmonotonic time dependence of the polarization rotation angle. This time dependence reflects transfer of the angular momentum from rotating molecules to the macroscopic gas flow, which may lead to the birth of gas vortices. Moreover, we show that the long-term behavior of the polarization rotation is sensitive to the details of the intermolecular potential. Thus, the polarization drag effect appears as a novel diagnostic tool for the characterization of intermolecular interaction potentials and studies of collisional processes in gases.

The elphbolt ab initio solver for the coupled electron-phonon Boltzmann transport equations

elphbolt is a modern Fortran (2018 standard) code for efficiently solving the coupled electron–phonon Boltzmann transport equations from first principles. Using results from density functional and density functional perturbation theory as inputs, it can calculate the effect of the non-equilibrium phonons on the electronic transport (phonon drag) and non-equilibrium electrons on the phononic transport (electron drag) in a fully self-consistent manner and obeying the constraints mandated by thermodynamics. It can calculate the lattice, charge, and thermoelectric transport coefficients for the temperature gradient and electric fields, and the effect of the mutual electron–phonon drag on these transport properties. The code fully exploits the symmetries of the crystal and the transport-active window to allow the sampling of extremely fine electron and phonon wave vector meshes required for accurately capturing the drag phenomena. The coarray feature of modern Fortran, which offers native and convenient support for parallelization, is utilized. The code is compact, readable, well-documented, and extensible by design.

Acoustic mechanism and characteristics of corrosion bubble rupture

Bubble rupture is one of the main acoustic emission (AE) sources for corrosion detection and the study of its acoustic characteristics is of great significance for corrosion identification. However, the stress state affects the form of bubble rupture, causing different acoustic characteristics. In this paper, the acoustic signal characteristics of two forms of bubble rupture and drag phenomena are investigated and the process of bubble rupture both near to and away from the metal surface is studied, mainly through theoretical calculation, numerical simulation and experimentation. A theoretical model of bubble rupture is established according to the volume of fluid (VOF) method. The finite element method is used to solve the plate displacement at the interface. Stress pulse theory is applied to calculate the AE signal amplitude of the bubble rupture. AE source characteristic parameters of the bubble rupture are then proposed. The experimental results demonstrate that the two forms of characteristics of the AE signals from corrosion bubble rupture are consistent with theoretical calculation and simulation results.

Experimental study of hard marine growth effect on the hydrodynamical behaviour of a submarine cable

Submarine cables such as electrical umbilical power cables for floating wind turbines are subject to biofouling which can have an important effect on their dynamical behaviour under wave and current conditions by drastically increasing their size and mass. The impact of biofouling on the dynamic behaviour of an underwater power cable characterized by the hydrodynamic coefficients, such as drag and inertia coefficients, must therefore be quantified. Hence, experiments have been carried out in a flume tank to compare the dynamics of a cylinder colonized by several kinds of roughnesses. The studied roughnesses concern realistic marine growth shapes and patterns with larger and sharper edges than those classically studied, in order to be more representative of hard fouling, such as Mytilus Edulis encountered on the western and north coasts of France. Seven configurations are tested with relative roughness coefficient ranging from roughness to cylinder diameter ratio up to 0.136. A specificity of this work is the highly realistic representation of the marine growth colonization through 3D printing covers, defined by statistical analysis of in situ observations and measurements. Tests are carried out using current only, then in line horizontal oscillating motions only and finally the combination of both, with the intention of reproducing specific wave and current conditions suitable for offshore applications. Using current conditions, the calculated coefficients are quite similar between configurations. However, the addition of oscillating motions to simulate wave induced motions has a significant impact on calculated results. The presence of roughness leads to a particular increase of drag and inertia phenomena. The Morison method used to characterize hydrodynamic coefficients in wave conditions is discussed in this paper.

Kinetic Processes in Fermi–Luttinger Liquids

In this work we discuss extensions of the pioneering analysis by Dzyaloshinskii and Larkin of correlation functions for one-dimensional Fermi systems, focusing on the effects of quasiparticle relaxation enabled by a nonlinear dispersion. Throughout the work we employ both, the weakly interacting Fermi gas picture and nonlinear Luttinger liquid theory to describe attenuation of excitations and explore the fermion-boson duality between both approaches. Special attention is devoted to the role of spin-exchange processes, effects of interaction screening, and integrability. Thermalization rates for electron- and hole-like quasiparticles, as well as the decay rate of collective plasmon excitations and the momentum space mobility of spin excitations are calculated for various temperature regimes. The phenomenon of spin-charge drag is considered and the corresponding momentum transfer rate is determined. We further discuss how momentum relaxation due to several competing mechanisms, viz. triple electron collisions, electron-phonon scattering, and long-range inhomogeneities affect transport properties, and highlight energy transfer facilitated by plasmons from the perspective of the inhomogeneous Luttinger liquid model. Finally, we derive the full matrix of thermoelectric coefficients at the quantum critical point of the first conductance plateau transition, and address magnetoconductance in ballistic semiconductor nanowires with strong Rashba spin-orbit coupling.

Aerodynamic Design of Wingtip Devices Using Far-field Drag Decomposition

Computational Fluid Dynamics (CFD) has become widely used for civil aircraft. However, the commonly used wall integration method for drag prediction based on Reynolds- averaged Navier-Stokes (RANS) equations still has some shortcomings. Far-field drag decomposition (FDD) method was developed as an alternative to improve the drag prediction accuracy and to provide a powerful analysis tool. FDD is capable of decomposing the drag into viscous, shock, induced, and spurious drag components, which provides invaluable insight into the relationship between drag and flow phenomena. Despite all the strengths, FDD is seldom used for aerodynamic shape design and optimization. In this paper, FDD was used to design wingtip devices for a business aircraft. Five spiroid and one blended winglet were compared with baseline wing and tip-extension configuration. Results indicate that all drag components were quantified successfully and the trade-off between induced drag and other drag components was better explained. The spiroid winglet with new foil gives the lowest total drag and wave drag.

KINETIC PROCESSES IN FERMI-LUTTINGER LIQUIDS

In this work we discuss extensions of the pioneering analysis by Dzyaloshinskii and Larkin of correlation functions for one-dimensional Fermi systems, focusing on the effects of quasiparticle relaxation enabled by a nonlinear dispersion. Throughout the work we employ both, the weakly interacting Fermi gas picture and nonlinear Luttinger liquid theory to describe attenuation of excitations and explore the fermion-boson duality between both approaches. Special attention is devoted to the role of spin-exchange processes, effects of interaction screening, and integrability. Thermalization rates for electron- and hole-like quasiparticles, as well as the decay rate of collective plasmon excitations and the momentum space mobility of spin excitations are calculated for various temperature regimes. The phenomenon of spin-charge drag is considered and the corresponding momentum transfer rate is determined. We further discuss how momentum relaxation due to several competing mechanisms, viz. triple electron collisions, electron-phonon scattering, and long-range inhomogeneities affect transport properties, and highlight energy transfer facilitated by plasmons from the perspective of the inhomogeneous Luttinger liquid model. Finally, we derive the full matrix of thermoelectric coefficients at the quantum critical point of the first conductance plateau transition, and address magnetoconductance in ballistic semiconductor nanowires with strong Rashba spin-orbit coupling.

On relativistic gasdynamics: invariance under a class of reciprocal-type transformations and integrable Heisenberg spin connections

A classical system of conservation laws descriptive of relativistic gasdynamics is examined. In the two-dimensional stationary case, the system is shown to be invariant under a novel multi-parameter class of reciprocal transformations. The class of invariant transformations originally obtained by Bateman in non-relativistic gasdynamics in connection with lift and drag phenomena is retrieved as a reduction in the classical limit. In the general 3+1-dimensional case, it is demonstrated that Synge’s geometric characterization of the pressure being constant along streamlines encapsulates a three-dimensional extension of an integrable Heisenberg spin equation.