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  • A review of the state-of-the-art nanofluid spray and jet impingement cooling
    Phys. fluids (IF 3.514) Pub Date : 2020-12-22
    Praveen Kumar Tyagi; Rajan Kumar; Pranab Kumar Mondal

    Nanofluid spray/jet impingement cooling is widespread and finds applications in many scientific and industrial paradigms. Because of these ubiquities of nanofluid spray/jet impingement cooling, this branch of fluid dynamics has attracted great attention from the scientific community. The performance of nanofluid spray/jet impingement cooling very often depends on the nanoparticle concentration, shape

    更新日期:2020-12-30
  • Thelaw of the wall: A new perspective
    Phys. fluids (IF 3.514) Pub Date : 2020-12-17
    Sk Zeeshan Ali; Subhasish Dey

    The law of the wall, regarded as one of the very few pieces of turbulence hypothesis, predicts the mean-velocity profile (MVP) in a wall-bound flow. For about nine decades, the underlying physics of the law is deemed to be governed by an ad hoc mixing-length hypothesis. Here, we seek the origin of the law, for the first time, with the aid of a new hypothesis, which we call the mixing-instability hypothesis

    更新日期:2020-12-30
  • Laser-driven Marangoni flow and vortex formation in a liquid droplet
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Krishnkumar Gupta; Kiran M. Kolwankar; Bhalchandra Gore; Jayashree A. Dharmadhikari; Aditya K. Dharmadhikari

    We present a systematic study of the laser-driven Marangoni flow and curvature induced vortex formation in a copper sulfate pentahydrate solution, visualized by dispersed carbon nanotube (CNT) bundles. The experiments are carried out using different objectives of numerical aperture (NA) in the range of 0.1–0.6 to investigate the effect of focusing on the flow dynamics. The flow velocities measured

    更新日期:2020-12-30
  • Pulsatile twin parallel jets through a flexible orifice with application to edge-to-edge mitral valve repair
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Maziar Sargordi; Anna Chtchetinina; Giuseppe Di Labbio; Hoi Dick Ng; Lyes Kadem

    Edge-to-edge repair is a procedure introduced to overcome mitral valve regurgitation. However, it leads to an unusual flow in the left ventricle characterized by twin parallel pulsed jets. This type of flow has not been extensively investigated in the literature. We set up a basic experiment to better characterize this type of flow from a fundamental point of view. Planar time-resolved particle image

    更新日期:2020-12-30
  • Extension at the downstream end of turbulent band in channel flow
    Phys. fluids (IF 3.514) Pub Date : 2020-12-04
    Jinsheng Liu; Yue Xiao; Linsen Zhang; Mogeng Li; Jianjun Tao; Shengjin Xu

    In this Letter, the velocity structures and the extension behavior of localized turbulent bands in channel flows are measured by particle image velocimetry in a plane parallel to the walls and are analyzed by comparing with direct numerical simulations at low Reynolds numbers. It is illustrated that the convection velocity of the band head (band’s downstream end) is not determined by the formation

    更新日期:2020-12-30
  • Compression ramp shock wave/boundary layer interaction control with high-frequency streamwise pulsed spark discharge array
    Phys. fluids (IF 3.514) Pub Date : 2020-12-09
    Mengxiao Tang; Yun Wu; Shanguang Guo; Hua Liang; Yanhao Luo

    A streamwise array of pulsed spark discharge operating at a high frequency of 10 kHz is used to control the shock wave/boundary layer interaction (SWBLI) induced by a 24° compression ramp (CR) in a Mach 2.0 flow. High-speed schlieren imaging at 50 000 frames/s is deployed for flow visualization. The schlieren snapshots, as well as statistics of the schlieren sequence, show that the intensity weakening

    更新日期:2020-12-30
  • Effects of space sizes on the dispersion of cough-generated droplets from a walking person
    Phys. fluids (IF 3.514) Pub Date : 2020-12-15
    Zhaobin Li; Hongping Wang; Xinlei Zhang; Ting Wu; Xiaolei Yang

    The dispersion of viral droplets plays a key role in the transmission of COVID-19. In this work, we analyze the dispersion of cough-generated droplets in the wake of a walking person for different space sizes. The air flow is simulated by solving the Reynolds-averaged Navier–Stokes equations, and the droplets are modeled as passive Lagrangian particles. Simulation results show that the cloud of droplets

    更新日期:2020-12-30
  • Evolution of the second mode in a hypersonic boundary layer
    Phys. fluids (IF 3.514) Pub Date : 2020-12-17
    Chuanhong Zhang

    The temporal and spatial evolution of the second-mode instabilities at the final stage of transition in a hypersonic boundary layer is investigated. Experiments are conducted on a flared cone in a Mach 6 wind tunnel using time-resolved Rayleigh-scattering flow visualization, fast-response pressure sensors. The second mode lifts up away from the wall and evolves into a hairpin-shaped vortex at the final

    更新日期:2020-12-30
  • Measurement of small droplet aerosol concentrations in public spaces using handheld particle counters
    Phys. fluids (IF 3.514) Pub Date : 2020-12-22
    G. Aernout Somsen; Cees J. M. van Rijn; Stefan Kooij; Reinout A. Bem; Daniel Bonn

    We measure aerosol persistence to assess the risk of transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in public spaces. Direct measurement of aerosol concentrations, however, has proven to be technically difficult; we propose the use of handheld particle counters as a novel and easily applicable method to measure aerosol concentrations. This allows us to perform measurements

    更新日期:2020-12-30
  • Computational analysis of hydrodynamic interactions in a high-density fish school
    Phys. fluids (IF 3.514) Pub Date : 2020-12-04
    Yu Pan; Haibo Dong

    Numerical simulations are employed to study hydrodynamic interactions between two-dimensional fish-like bodies under a traveling wavy lateral motion in high-density diamond-shaped fish schools. This study focuses on two different streamwise spacings, a dense school with 0.4 body length (BL) spacing and a sparse school with 2.0 BL spacing, respectively. An immersed-boundary-method-based incompressible

    更新日期:2020-12-30
  • Stochastic fluid dynamics simulations of the velocity distribution in protoplasmic streaming
    Phys. fluids (IF 3.514) Pub Date : 2020-12-07
    Vladislav Egorov; Olga Maksimova; Irina Andreeva; Hiroshi Koibuchi; Satoshi Hongo; Shinichiro Nagahiro; Toshiyuki Ikai; Madoka Nakayama; Shuta Noro; Tetsuya Uchimoto; Jean-Paul Rieu

    Protoplasmic streaming in plant cells is directly visible in the cases of Chara corallina and Nitella flexilis, and this streaming is understood to play a role in the transport of biological materials. For this reason, related studies have focused on molecular transportation from a fluid mechanics viewpoint. However, the experimentally observed distribution of the velocity along the flow direction

    更新日期:2020-12-30
  • Scaling the vorticity dynamics in the leading-edge vortices of revolving wings with two directional length scales
    Phys. fluids (IF 3.514) Pub Date : 2020-12-22
    Nathaniel H. Werner; Junshi Wang; Haibo Dong; Azar Eslam Panah; Bo Cheng

    In revolving or flapping wings, radial planetary vorticity tilting (PVTr) is a mechanism that contributes to the removal of radial (spanwise) vorticity within the leading-edge vortex (LEV), while vorticity advection increases its strength. Dimensional analysis predicts that the PVTr and advection should scale with the wing aspect-ratio (AR) in identical fashion, assuming a uniform characteristic length

    更新日期:2020-12-30
  • Effects of time-varying flexibility on the propulsion performance of a flapping foil
    Phys. fluids (IF 3.514) Pub Date : 2020-12-24
    Guangyu Shi; Qing Xiao; Qiang Zhu

    In this paper, we numerically investigate the effects of time-varying bending stiffness on the propulsion performance of a flapping foil using a fully coupled fluid-structure interaction model. The flow field is simulated using a Navier–Stokes solver while the structural dynamics is resolved by a nonlinear beam model. The force generation, the passive deformation, and the flow field of the flexible

    更新日期:2020-12-30
  • Two-dimensional convection–diffusion in multipolar flows with applications in microfluidics and groundwater flow
    Phys. fluids (IF 3.514) Pub Date : 2020-12-01
    Etienne Boulais; Thomas Gervais

    Advection–diffusion in two-dimensional plane flows plays a key role in numerous transport problems in physics, including groundwater flow, micro-scale sensing, heat dissipation, and, in general, microfluidics. However, transport profiles are usually only known in a purely convective approximation or for the simplest geometries, such as for quasi one-dimensional planar microchannels. This situation

    更新日期:2020-12-30
  • Electrohydrodynamic analysis of bubble burst in large Leidenfrost droplets
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Onur Ozkan; Vaibhav Bahadur

    A thin vapor gap forms underneath a liquid drop on a sufficiently hot surface, which prevents solid–liquid contact (the Leidenfrost effect). This vapor gap can be partly eliminated by applying an electrical potential difference across the vapor gap to electrostatically suppress the Leidenfrost state. An interesting hydrodynamics-related phenomenon that can occur in Leidenfrost droplets is the formation

    更新日期:2020-12-30
  • Hydrodynamics rheological impact of an oscillatory electroosmotic flow on a mass transfer process in a microcapillary with a reversible wall reaction
    Phys. fluids (IF 3.514) Pub Date : 2020-12-08
    G. Mederos; J. Arcos; O. Bautista; F. Méndez

    In this work, we carry out a theoretical analysis of the mass transport rate through a long microcapillary, with a reactive wall, connecting two reservoirs with different concentrations of some electro-neutral solute, caused by an oscillatory electroosmotic flow of a Jeffreys fluid. The mass transport enhancement relative to that caused only by molecular diffusion is found to be a function of the following

    更新日期:2020-12-30
  • Pore-scale investigation of immiscible gas-assisted gravity drainage
    Phys. fluids (IF 3.514) Pub Date : 2020-12-11
    Debin Kong; Peiqing Lian; Weiyao Zhu; Yiqiang Li

    Gas-assisted gravity drainage (GAGD) is an effective method of oil recovery that is influenced by the properties of the fluids and formations involved. In this paper, a direct numerical simulation method is employed to investigate immiscible GAGD in an oil-wet porous medium. The interface between oil and gas is tracked via the phase-field method. A series of numerical simulations are performed over

    更新日期:2020-12-30
  • Electroosmotic thrusters in soft nanochannels for space propulsion
    Phys. fluids (IF 3.514) Pub Date : 2020-12-17
    Jiaxuan Zheng; Yongjun Jian

    Space propulsion of electroosmotic thrusters (EOTs) with a soft charged nanochannel is investigated considering the Navier slip boundary and constant surface charge density on the walls of slit channels. The soft nanochannel is characterized by a wall-grafted ion-penetrable charged polyelectrolyte layer (PEL). The Poisson–Boltzmann equation is solved to give the electric potential distribution based

    更新日期:2020-12-30
  • Electric field modulated deformation dynamics of a compound drop in the presence of confined shear flow
    Phys. fluids (IF 3.514) Pub Date : 2020-12-21
    Somnath Santra; Anirban Jana; Suman Chakraborty

    Dynamics of compound drops is central in several emerging applications including emulsion-fueled direct injection, targeted drug delivery, and the development of mechano-sensitive artificial cells. These applications are commonly hallmarked by high shear rates in confined fluidic environments. In the present work, we depict the role of the transverse electric field in controlling the resulting morpho-dynamics

    更新日期:2020-12-30
  • Flows between parallel plates: Analytical solutions of regularized 13-moment equations for inverse-power-law models
    Phys. fluids (IF 3.514) Pub Date : 2020-12-22
    Zhicheng Hu; Siyao Yang; Zhenning Cai

    We study the structure of stationary channel flows predicted by the regularized 13-moment equations. Compared with the work of Taheri et al. [“Couette and Poiseuille microflows: Analytical solutions for regularized 13-moment equations,” Phys. Fluids 21, 017102 (2009)], we focus on gases whose molecules satisfy the general inverse power law. The analytical solutions are obtained for the semi-linear

    更新日期:2020-12-30
  • Analytical investigation of the nonlinear dynamics of empty spherical multi-bubbles in hydrodynamic cavitation
    Phys. fluids (IF 3.514) Pub Date : 2020-12-23
    Yupeng Qin; Zhen Wang; Li Zou

    The nonlinear dynamics of empty multi-bubbles with the same distance and initial conditions are studied analytically through a modified Rayleigh–Plesset equation. The collapse time and analytical solution are derived under various initial conditions. In particular, when considering a positive initial vibration velocity, the exact analytical expression for the maximal radius is obtained by solving a

    更新日期:2020-12-30
  • Hybrid continuum-molecular modeling of fluid slip flow
    Phys. fluids (IF 3.514) Pub Date : 2020-12-29
    Mohamed Shaat

    Experiments on fluid systems in micro-/nano-scale solid conveyors have shown a violation of the no-slip assumption that has been adopted by the classical fluid mechanics. To correct this mechanics for the fluid slip, various approaches have been proposed to determine the slip boundary conditions. However, these approaches have revealed contradictory results for a variety of systems, and a debate on

    更新日期:2020-12-30
  • Dynamics of formation of poly(vinyl alcohol) filaments with an energetically efficient micro-mixing mechanism
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Alberto Ramos-Escobar; Rafael Uceda-Gallegos; Luis Modesto-López; Alfonso Gañán-Calvo

    We present a pneumatic approach for massive production of poly(vinyl alcohol) (PVA) filaments based on a mixing mechanism at the micrometer scale using so-called Flow Blurring (FB) atomizers. This micro-mixing is triggered by a turbulent, bubbly motion generated by implosion of a gas current into a liquid feeding tube. The energy of the gas, the liquid viscosity, and the geometry of the atomizer play

    更新日期:2020-12-30
  • Sessile drop response to a single wave electrokinetic excitation
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Juan S. Marin Quintero; Prashant R. Waghmare

    The response time for maximum drop deformation and its comparison with different time scales is established and verified with experiments. The applied fluctuation is achieved by applying a single wave perturbation of electrowetting with desired amplitude and frequency. To pinpoint the importance of the initial actuation conditions, the variance in the maximum drop deformation for a single wave perturbation

    更新日期:2020-12-30
  • Instability and energy budget analysis of viscous coaxial jets under a radial thermal field
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Ran Qiao; Kai Mu; Xisheng Luo; Ting Si

    Temporal linear instability of viscous coaxial jets under a radial thermal field is carried out by considering axisymmetric and non-axisymmetric disturbances. The interfacial tensions of different fluids are taken to be temperature dependent. The para-sinuous, para-varicose, and helical unstable modes are identified in the Rayleigh regime. The energy budget is also employed to explore the relative

    更新日期:2020-12-30
  • Numerical study of bubbly flow in a swirl atomizer
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Erkki Laurila; Daulet Izbassarov; Mika Järvinen; Ville Vuorinen

    In this work, we extend our previous research on swirl nozzles by introducing bubbles at the nozzle inlet. A large-scale hollow cone pressure-swirl atomizer is studied using scale-resolving simulations. The present flow conditions target a Reynolds number range of 600 ≤ Re ≤ 910 and gas-to-total volumetric flow rate ratios between 0.07 ≤ β ≤ 0.33 with β = 0 as an experimental and computational reference

    更新日期:2020-12-30
  • Modeling surfactant-laden droplet dynamics by lattice Boltzmann method
    Phys. fluids (IF 3.514) Pub Date : 2020-12-04
    Yajing Zong; Chunhua Zhang; Hong Liang; Lu Wang; Jiangrong Xu

    Based on the phase-field theory, we present an improved lattice Boltzmann (LB) method for simulating droplet dynamics with soluble surfactants. This method takes advantage of three sets of particle distribution functions for solving the coupled system of two Cahn–Hilliard-like equations and incompressible Navier–Stokes equations. The phase-field model is formulated from the perspective of the Ginzburg–Landau

    更新日期:2020-12-30
  • Simulation of shock induced vapor condensation flows in the Lennard-Jones fluid by microscopic and continuum models
    Phys. fluids (IF 3.514) Pub Date : 2020-12-08
    A. Frezzotti; P. Barbante

    The vapor condensation onto a thin liquid film, induced by the reflection of a weak shock wave, is studied by molecular dynamics atomistic simulations of a simple Lennard-Jones fluid. Molecular dynamics results provide reference flowfields for two models. The first one adopts a hybrid continuum-kinetic description in which the liquid phase is described by hydrodynamic equations, whereas the vapor is

    更新日期:2020-12-30
  • On the instability of the melting film over a moving hot plate
    Phys. fluids (IF 3.514) Pub Date : 2020-12-09
    G. M. Sisoev; G. Çekiç

    The flow of a viscous film emerging over a plate moving through a linear elastic solid in the case when the plate temperature exceeds the melting temperature of the solid is studied. An approximate model for the melting film flow and the solid temperature is stated in the case of known dependencies of the kinematic viscosity and thermal conductivity of the melt on temperature. In the case of constant

    更新日期:2020-12-30
  • Asymmetric splash and breakup of drops impacting on cylindrical superhydrophobic surfaces
    Phys. fluids (IF 3.514) Pub Date : 2020-12-09
    Haixiang Zhang; Xiwen Zhang; Xian Yi; Feng He; Fenglei Niu; Pengfei Hao

    Drop splash and breakup on cylindrical surfaces play an important role in a wide variety of industrial applications. In this work, water drops with a wide range of impact velocities (1.4 m/s–4.5 m/s) and cylindrical stainless steels with different diameters (1 mm–20 mm) are employed to investigate the asymmetric splash and breakup characteristics of drops impacting on cylindrical superhydrophobic surfaces

    更新日期:2020-12-30
  • Splashing of liquid droplet on a vibrating substrate
    Phys. fluids (IF 3.514) Pub Date : 2020-12-09
    T. I. Khabakhpasheva; A. A. Korobkin

    The unsteady axisymmetric problem of a liquid drop impacting onto a rigid vibrating substrate is studied. Initially, the drop is spherical and touches the flat substrate at a single point. Then, the substrate starts to move toward the drop and vibrate with a small amplitude and high frequency. The early stage of the impact is studied by using the potential flow theory and the Wagner approach in dimensionless

    更新日期:2020-12-30
  • Impact on mechanical robustness of water droplet due to hydrophilic nanoparticles
    Phys. fluids (IF 3.514) Pub Date : 2020-12-10
    Jiandong Zhou; Xin Wang; Jinzhan Su; Dengwei Jing; A. A. Mohamad

    The mechanical robustness of droplets is a crucial factor for many applications. In the present work, we reported that adding a small and certain number of hydrophilic nanoparticles can significantly enhance the mechanical robustness of water droplets. Among the various hydrophilic nanoparticles investigated, SiO2 was found to be the most effective one. Experiments and molecular dynamics simulations

    更新日期:2020-12-30
  • Effect of Reynolds number on drag reduction in turbulent boundary layer flow over liquid–gas interface
    Phys. fluids (IF 3.514) Pub Date : 2020-12-11
    Hongyuan Li; SongSong Ji; Xiangkui Tan; Zexiang Li; Yaolei Xiang; Pengyu Lv; Huiling Duan

    The liquid–gas interface (LGI) on submerged microstructured surfaces has the potential to achieve a large slip effect, which is significant to the underwater applications such as drag reduction. The mechanism of drag reduction in the laminar flow over the LGI has been well recognized, while it is yet not clear for the turbulent boundary layer (TBL) flow over the LGI. In the present work, an experimental

    更新日期:2020-12-30
  • Oblique droplet impact on superhydrophobic surfaces: Jets and bubbles
    Phys. fluids (IF 3.514) Pub Date : 2020-12-11
    Jianwei Guo; Song Zou; Shiji Lin; Binyu Zhao; Xu Deng; Longquan Chen

    Previous studies revealed that the perpendicular impact of low-viscosity droplets on sufficiently lyophobic surfaces would stimulate a liquid jet during droplet recoiling, and in some cases, it is accompanied with the entrapment of an air bubble. However, whether such free-surface flow phenomena occur in oblique droplet impact and how surface inclinations influence the dynamics remain open questions

    更新日期:2020-12-30
  • A high order spectral difference-based phase field lattice Boltzmann method for incompressible two-phase flows
    Phys. fluids (IF 3.514) Pub Date : 2020-12-11
    Chao Ma; Jie Wu; Tongwei Zhang

    In this paper, a high order spectral difference-based phase field lattice Boltzmann method (SD-PFLBM) is proposed for simulating incompressible two-phase flows. The spectral difference method (SDM) is used to discretize the convection term and the gradient term of the discrete Boltzmann equation for obtaining the flow field. Moreover, the SDM is also adopted to discretize the convection term and the

    更新日期:2020-12-30
  • Bubble entrapment during head-on binary collision with large deformation of unequal-sized tetradecane droplets
    Phys. fluids (IF 3.514) Pub Date : 2020-12-15
    Nitin Goyal; Javed Shaikh; Atul Sharma

    Head-on collision dynamics of unequal-sized binary tetradecane droplets in air is numerically studied for numerous diameter ratios Dr = 1.5–2.5 and larger values of Weber number We = 50–220. Our study is within two collision regimes, permanent coalescence and separation after temporary coalescence, where entrapment of an air bubble is revealed at larger We and intermediate values of Dr. We found two

    更新日期:2020-12-30
  • Partial coalescence of a drop on a larger-viscosity pool
    Phys. fluids (IF 3.514) Pub Date : 2020-12-15
    Abdullah A. Alhareth; Sigurdur T. Thoroddsen

    When a low-viscosity drop coalesces with a pool surface of the same liquid, it often portrays partial coalescence, where it pinches off a daughter droplet from its top. Such partial coalescence can also occur for a drop spreading on a strongly hydrophilic solid surface. Herein, we investigate the partial coalescence of a low-viscosity drop with a pool surface, when the viscosity of the miscible pool

    更新日期:2020-12-30
  • Influence of thermal gradients on the invasion patterns during drying of porous media: A lattice Boltzmann method
    Phys. fluids (IF 3.514) Pub Date : 2020-12-16
    Debashis Panda; Shubhani Paliwal; Dasika Prabhat Sourya; Abdolreza Kharaghani; Evangelos Tsotsas; Vikranth Kumar Surasani

    Drying of porous media sounds simple yet complicated to study the multiphase flow counterparts in porous media with intricate pore geometries. In the past, we have discussed the Lattice Boltzmann Model (LBM) as a powerful multiphase solver for the drying of porous media. In this study, we extend our previous work on the Shan Chen representation of the multiphase LBM to drying of porous media with imposed

    更新日期:2020-12-30
  • Numerical investigation of surface curvature effect on the self-propelled capability of coalesced drops
    Phys. fluids (IF 3.514) Pub Date : 2020-12-18
    Ahmed Islam; Mark Sussman; Yongsheng Lian

    We numerically investigate the curvature effect on the self-propelled capability of coalesced drops. The numerical method is based on a well validated multiphase flow solver that solves the three-dimensional Navier–Stokes equations. The liquid–air interface is captured using the moment of fluid method, and a direction splitting method is applied to advect the interface. Afterward, an approximate projection

    更新日期:2020-12-30
  • Bouncing of cloud-sized microdroplets on superhydrophobic surfaces
    Phys. fluids (IF 3.514) Pub Date : 2020-12-21
    Hany Gomaa; Moussa Tembely; Nabil Esmail; Ali Dolatabadi

    The control of microdroplet impact on superhydrophobic surfaces (SHSs) is becoming imperative owing to its effect on several industrial applications, such as corrosion protection, self-cleaning, ice resisting, and de-icing. While most of the experimental studies on the impact dynamics of droplets are based on macrodroplets, it is unclear how the obtained results can be applied to microdroplet impact

    更新日期:2020-12-30
  • Experimental study on the trajectory of projectile water entry with asymmetric nose shape
    Phys. fluids (IF 3.514) Pub Date : 2020-12-21
    Yao Shi; Yang Hua; Guang Pan

    In this study, we investigated the water entry trajectory characteristics of a projectile with an asymmetric nose shape at different initial impact velocities and impact angles experimentally. With high speed photography, the water entry cavities and projectile motions were captured to obtain the trajectory curve and the attitude angle of the projectile. Compared to the projectile with a flat nose

    更新日期:2020-12-30
  • Rogue waves associated with resonant slow sloshing waves spontaneously excited in wind-driven water wave turbulence
    Phys. fluids (IF 3.514) Pub Date : 2020-12-22
    Ji-Lin Jou; Wei-Shuo Lo; Lin I

    Rogue wave events (RWEs), rare uncertainly emerging localized events with extreme amplitudes, widely exist in various nonlinear wave media. Past laboratory studies on RWEs of water surface waves have mainly focused on mechanically excited waves but to a lesser extent on waves solely excited by wind, which also have a large number of degrees of freedom. In this work, we experimentally demonstrate the

    更新日期:2020-12-30
  • A three-fluid model for the dissipation of interfacial capillary-gravity waves
    Phys. fluids (IF 3.514) Pub Date : 2020-12-23
    Girish Kumar Rajan

    We investigate the dissipation of linear, two-dimensional, interfacial waves in a setting comprising three fluids (an upper fluid of semi-infinite depth, a middle fluid-layer of finite thickness, and a lower fluid of semi-infinite depth) separated by two distinct interfaces, which we consider to be elastic. We derive analytic expressions for the dissipation rate of capillary-gravity waves in such a

    更新日期:2020-12-30
  • A lattice Boltzmann modeling of viscoelastic drops’ deformation and breakup in simple shear flows
    Phys. fluids (IF 3.514) Pub Date : 2020-12-01
    Danielle S. Tan; Boo Cheong Khoo; Nhan Phan-Thien

    The deformation and breakup of viscoelastic drops in simple shear flows of Newtonian liquids are studied numerically. Our three-dimensional numerical scheme, extended from our previous two-dimensional algorithm, employs a diffusive-interface lattice Boltzmann method together with a lattice advection–diffusion scheme, the former to model the macroscopic hydrodynamic equations for multiphase fluids and

    更新日期:2020-12-30
  • Fractional characterization of fluid and synergistic effects of free convective flow in circular pipe through Hankel transform
    Phys. fluids (IF 3.514) Pub Date : 2020-12-02
    Kashif Ali Abro

    Although heat transfer by transient free convection has been investigated with different cross sections such as elliptical cones, rectangular or square ducts, and triangular plates, none of the analytical study of a circular cylinder in free space via fractional calculus approaches with sinusoidal conditions is explored. This manuscript presents fractional modeling of a circular cylinder to observe

    更新日期:2020-12-30
  • Acoustic streaming in second-order fluids
    Phys. fluids (IF 3.514) Pub Date : 2020-12-04
    Pradipta Kr. Das; Arthur David Snider; Venkat R. Bhethanabotla

    In this article, inner acoustic streaming for second-order fluids has been studied analytically by employing asymptotic expansions for a thin Stokes layer and low acoustic Mach number. In addition, a multiple-timescale approach has been adopted to separate the primary oscillatory flow and the steady acoustic streaming. The study considers two sample cases: (i) motionless boundary and (ii) vibrating

    更新日期:2020-12-30
  • Pressure-driven flows of a thixotropic viscoplastic material: Performance of a novel fluidity-based constitutive model
    Phys. fluids (IF 3.514) Pub Date : 2020-12-04
    J. P. Cunha; P. R. de Souza Mendes; I. R. Siqueira

    This paper examines pressure-driven tube flows of inelastic yield-stress materials with thixotropic effects. In contrast to previous works based on structural kinetic models, we employ a fluidity-based constitutive model that uses the material fluidity as a measure of the material structuring level. The model relies on rheological material properties that can be determined from standard experimental

    更新日期:2020-12-30
  • Unsteady flow of Carreau fluids around an impulsively moving cylinder
    Phys. fluids (IF 3.514) Pub Date : 2020-12-28
    Yeji Yun; Solkeun Jee; Junseong Lee

    Unsteady flow of Carreau fluids around an impulsively moving circular cylinder is numerically investigated in this study. Both shear-thinning and shear-thickening fluids are used with the range of the power-index number 0.4 ≤ n ≤ 2. Unsteady laminar flow with the influence of shear-dependent viscosity and impulsive motions of the cylinder are analyzed with various Carreau numbers 10 ≤ Cu ≤ 40 and Reynolds

    更新日期:2020-12-30
  • A microstructure model for viscoelastic–thixotropic fluids
    Phys. fluids (IF 3.514) Pub Date : 2020-12-29
    K. Le-Cao; N. Phan-Thien; N. Mai-Duy; S. K. Ooi; A. C. Lee; B. C. Khoo

    A microstructure model to describe the viscoelasticity and thixotropy properties of complex fluids is proposed. The model is based on the Lodge–Yamamoto network theory and is an extension of the Phan-Thien–Tanner model, with a kinetic process in which specific forms of creation and destruction rates are assumed. The final equation is simple with a small number of empirical parameters required and can

    更新日期:2020-12-30
  • The perspective of fluid flow behavior of respiratory droplets and aerosols through the facemasks in context of SARS-CoV-2
    Phys. fluids (IF 3.514) Pub Date : 2020-11-24
    Sanjay Kumar

    In the unfortunate event of the current ongoing pandemic COVID-19, where vaccination development is still in the trial phase, several preventive control measures such as social distancing, hand-hygiene, and personal protective equipment have been recommended by health professionals and organizations. Among them, the safe wearing of facemasks has played a vital role in reducing the likelihood and severity

    更新日期:2020-12-01
  • Machine learning open-loop control of a mixing layer
    Phys. fluids (IF 3.514) Pub Date : 2020-11-04
    Bernd R. Noack

    We develop an open-loop control system using machine learning to destabilize and stabilize the mixing layer. The open-loop control law comprising harmonic functions is explored using the linear genetic programming in a purely data-driven and model-free manner. The best destabilization control law exhibits a square wave with two alternating duty cycles. The forced flow presents a 2.5 times increase

    更新日期:2020-12-01
  • Cold atmospheric plasma for SARS-CoV-2 inactivation
    Phys. fluids (IF 3.514) Pub Date : 2020-11-10
    Gustavo GarciaJr.; Vaithilingaraja Arumugaswami; Richard E. Wirz

    Syndrome coronavirus 2 (SARS-CoV-2) infectious virions are viable on various surfaces (e.g., plastic, metals, and cardboard) for several hours. This presents a transmission cycle for human infection that can be broken by developing new inactivation approaches. We employed an efficient cold atmospheric plasma (CAP) with argon feed gas to inactivate SARS-CoV-2 on various surfaces including plastic, metal

    更新日期:2020-12-01
  • Flow visualization of an N95 respirator with and without an exhalation valve using schlieren imaging and light scattering
    Phys. fluids (IF 3.514) Pub Date : 2020-11-10
    Matthew Staymates

    This work demonstrates the qualitative fluid flow characteristics of a standard N95 respirator with and without an exhalation valve. Schlieren imaging was used to compare an adult male breathing through an N95 respirator with and without a valve. The schlieren imaging technique showed the flow of warm air passing through these respirators but did not provide information about droplet penetration. For

    更新日期:2020-12-01
  • Structures of liquid jets in supersonic crossflows in a rectangular channel with an expansion section
    Phys. fluids (IF 3.514) Pub Date : 2020-11-13
    Jiafeng Zhao; Yiheng Tong; Yongjie Ren; Yangzhu Zhu; Zhi Chen; Wei Lin; Wansheng Nie

    The structures of liquid jets in supersonic crossflows (LJISC) are characterized by using high-speed photography and shadowgraph techniques. These flow structures substantially interfere with the atomization and mixing of the jet. Experimental studies on flow and spray fields are performed under various Mach numbers, injection positions, and injection angles. The results establish that (1) the evolution

    更新日期:2020-12-01
  • Correction and improvement of a widely used droplet–droplet collision outcome model
    Phys. fluids (IF 3.514) Pub Date : 2020-11-17
    Shaoyi Suo; Ming Jia

    The widely used droplet–droplet collision outcome model distinguishing stretching separation (SS) and fast coalescence (FC) (named SS/FC model) proposed by Jiang et al. [J. Fluid Mech. 234, 171 (1992)] is corrected and improved in this study. By re-deriving the momentum conservation, the correct mathematical expression of the tangential velocity along the sliding direction is obtained. Moreover, to

    更新日期:2020-12-01
  • How coronavirus survives for days on surfaces
    Phys. fluids (IF 3.514) Pub Date : 2020-11-24
    Rajneesh Bhardwaj; Amit Agrawal

    Our previous study [R. Bhardwaj and A. Agrawal, “Likelihood of survival of coronavirus in a respiratory droplet deposited on a solid surface,” Phys. Fluids 32, 061704 (2020)] showed that the drying time of typical respiratory droplets is on the order of seconds, while the survival time of the coronavirus on different surfaces was reported to be on the order of hours in recent experiments. We attribute

    更新日期:2020-12-01
  • Liquid-curtain-based strategy to restrain plume during flushing
    Phys. fluids (IF 3.514) Pub Date : 2020-11-23
    Su-Chen Wu; Meng-Yue Guo; Ji-Xiang Wang; Shuhuai Yao; Jun Chen; Yun-yun Li

    How to prevent the flushing-induced plume without changing people’s daily habits? Enlightened by thoughts of redesigning the restroom, this article provides a redesigned toilet using liquid-curtain-based strategy and verifies its advantages from the computational fluid dynamics. Two favorable effects are spotted: (1) the liquid curtain can suppress the upward virus particles (only 1% viruses can be

    更新日期:2020-12-01
  • Pulsed-jet propulsion of a squid-inspired swimmer at high Reynolds number
    Phys. fluids (IF 3.514) Pub Date : 2020-11-03
    Yang Luo; Qing Xiao; Qiang Zhu; Guang Pan

    An inflation–deflation propulsion system inspired by the jet propulsion mechanism of squids and other cephalopods is proposed. The two-dimensional squid-like swimmer has a flexible mantle body with a pressure chamber and a nozzle that serves as the inlet and outlet of water. The fluid–structure interaction simulation results indicate that larger mean thrust production and higher efficiency can be achieved

    更新日期:2020-12-01
  • Specialization of tuna: A numerical study on the function of caudal keels
    Phys. fluids (IF 3.514) Pub Date : 2020-11-06
    Jun-Duo Zhang; Hyung Jin Sung; Wei-Xi Huang

    Tunas are known for their extraordinary swimming performance, which is accomplished through various specializations. The caudal keels, a pair of lateral keel-like structures along the caudal peduncle, are a remarkable specialization in tunas and have convergently arisen in other fast-swimming marine animals. In the present study, the hydrodynamic function of caudal keels in tuna was numerically investigated

    更新日期:2020-12-01
  • An experimental study of respiratory aerosol transport in phantom lung bronchioles
    Phys. fluids (IF 3.514) Pub Date : 2020-11-06
    Arnab Kumar Mallik; Soumalya Mukherjee; Mahesh V. Panchagnula

    The transport and deposition of micrometer-sized particles in the lung is the primary mechanism for the spread of aerosol borne diseases such as corona virus disease-19 (COVID-19). Considering the current situation, modeling the transport and deposition of drops in human lung bronchioles is of utmost importance to determine their consequences on human health. The current study reports experimental

    更新日期:2020-12-01
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