Recent studies have suggested that a cyclonic vortex, which has the same signed vorticity as that of background shear, can lead to dissimilar heat transfer enhancement, i.e. more heat transfer than momentum transfer. However, it has not yet been known how the cyclonic vortex achieves dissimilarity, or if other types of vortices would also lead to dissimilarity. In order to tackle these problems, we

In the presence of an electromagnetic field, we studied the stability of a conductive thin liquid film flowing on a non-conductive inclined plate taking the effect of odd viscosity into account. Using the lubrication theory, a new liquid–gas interface evolution equation involving odd viscosity effect is derived. By analyzing the linear and non-linear stability of the evolution equation, we find that

The present work reviews the recent developments in the domain of particle image velocimetry (PIV) with attention to its use for large-scale problems of interest for industrial aerodynamics. The article introduces the fundamental principles of flow seeding for large-scale experiments based on the helium-filled soap bubble (HFSB) technique. The measurement of flow tracers in a three-dimensional domain

The research is devoted to the stability of convective flow in a nonuniformly rotating layer of an electrically conducting fluid in a spiral magnetic field. The stationary and oscillatory modes of magnetic convection are considered depending on the profile of the angular rotation velocity (Rossby number Ro) and on the profile of the external azimuthal magnetic field (magnetic Rossby number Rb). The

Here we consider the case of a train of linear water waves incident on a bottom-mounted surface-piercing compound partial-porous cylinder consisting of two coaxial cylinders of which the upper cylinder is hollow with a thin porous side wall and the lower cylinder, with radius greater than that of the upper one, is rigid. Subsequently, we examine the associated hydrodynamic forces. Using linear water

In this paper we perform large eddy simulations of variable density mixing layers, which originate from initially laminar conditions. The aim of this work is to capture the salient flow physics present in the laboratory flow. This is achieved through varying the nature of the inflow condition, and assessing the vortex structure present in the flow. Two distinct inflow condition types are studied; the

This paper deals with the active control of the compressible flow past a bluff-body by means of external acoustic sources. We successfully suppress the transition leading to the von-Karman vortex street. The derived adjoint-based framework allows the determination of the corresponding acoustic sources for generic bluff-body shapes. In particular, we determine the optimal spatial position for the control

Flow past objects in microfluidics and microscale devices are used to perturb the flow and thereby achieve effective mixing and heat transfer. This paper presents the observations on the flow past bluff (elliptical, rectangular and triangular) cylindrical micropillars (objects) having different cross-sectional area in a micro-channel through 2D simulations. The pertinent range of Re based on object

Numerical simulations of violent bubble dynamics are often associated with numerical instabilities at the end of collapse, when a shock wave is emitted. Based on the Keller–Miksis equation, we show that this is caused by two time scales associated with the phenomenon. Nonsingular equations are thus formed based on asymptotic expansion theory and the time derivatives of the bubble radius are shown to

The dynamic behavior of flow over a circular main cylinder (MC) in presence of single small rotating control cylinder (CC) has been studied numerically at Reynolds number, Re = 100 and 200. The CC location (r cc = 0.6D–1D), rotational direction (clockwise and counterclockwise) and rotational rate (α = 0–2) of CC are taken as the study parameters. The flow field variables are computed using Ansys Fluent

Role of endothelium glycocalyx integraty is important for targeted intravenous nanoparticle drug delivery. It plays a vital role in many physical functions in microvessel including protection of the vessel wall with harmful levels of fluid shear. Hence, understanding the impact of the glycocalyx layer is important to develop of human medicine for the treatment of cardiovascular disorders. By experiment

A novel aerodynamic measure, an arch mounted leeward of a circular cylinder, is proposed to reduce drag and mitigate vortex shedding for a circular cylinder. To confirm the validity of the proposed measure, the aerodynamic forces were measured through a force meter at the end of a cylinder, the wind pressure was measured at seven cross-sections of the cylinder, and elastically mounted cylinders were

We consider rotationally driven three-dimensional nonlinear polymeric fiber jets with the effect of gravity force. We implement an empirical viscosity model for the polymeric fluid of such flows to investigate the properties of the three-dimensional polymeric fiber jets generated by the imposed rotational forces. We apply theoretical and numerical techniques to determine the expressions for the leading

A detailed investigation of the flow in a steady lid-driven cavity of depth to width ratio 1:2 containing a circular cylinder is provided. Three different Reynolds numbers (based on the lid velocity and cavity depth) of 100, 500 and 1000 as well as four different cylinder radii to cavity depth ratios (0.1, 0.2, 0.3 and 0.4) located at three different positions along the horizontal centerline of the

We investigate the capability of machine learning (ML) based reduced order model (ML-ROM) for two-dimensional unsteady flows around a circular cylinder at different Reynolds numbers. The present ML-ROM is constructed by two ML schemes: a convolutional neural network-based autoencoder (CNN-AE) and a long short-term memory (LSTM). The CNN-AE is utilized to map high-dimensional flow fields obtained by

The effect of impeller geometry on bubble breakage in a stirred tank was investigated for a range of impeller Reynolds number (Re) using a high speed imaging method. The bubble dynamic behavior and breakage mechanism were investigated for four different impeller geometries namely, two-flat blades impeller, four-flat blades impeller, four-twisted blades impeller, and two-pinned blades impeller. The

Spiral wound membrane modules operate as filtration modules in the food, beverage, and pharmaceutical industries. As many fluids are non-Newtonian or become non-Newtonian during concentration, it is essential to gain an understanding of the effect of a shear-rate dependent viscosity. This computational work examines the impact of the fluid rheology and the Reynolds number on the hydrodynamics and the

We analyze a suspension of deformable particles in a pressure-driven flow. The suspension is composed of neutrally buoyant initially spherical particles and a Newtonian carrier fluid, and the flow is solved by means of direct numerical simulations, using a fully Eulerian method based on a one-continuum formulation. The solid phase is modeled with an incompressible viscous hyperelastic constitutive

The article explores the governing role of the internal soluto-thermal hydrodynamics and advective transport within sessile colloidal droplets on the self-assembly of nanostructures to form floral patterns. Water–acetone mixture and Bi2O3 nanoflakes based complex fluids are used as the experimental liquids. Micro-liter sessile droplets are allowed to vaporize and the dry-out patterns are examined using

Controlling the destructive behavior of the wake region and consequently drag reduction are great challenges in fluid mechanics and ocean engineering. In this paper, the effect of the non-uniform magnetic field on controlling the flow and consequently drag reduction has been studied in laminar flow of magnetic nanofluid around a circular cylinder. The source of the magnetic field is a single current-carrying

This paper focusses on a theoretical analysis of the entropic generation and heat-transfer characteristics of electromagnetohydrodynamic (EMHD) flow in vertical hydrophobic microchannels. The flow viscosity, electrical conductivity, and thermal conductivity are assumed to be temperature variant. The fluid velocity and energy transfer equations associated with a system of coupled non-linear equations

Particle refinement technique uses spatially varying particle distributions that focus fine resolution on areas of interest to improve accuracy and computational efficiency of the smooth particle hydrodynamics (SPH) method, but its stability at coarse/fine interfaces can be problematic. Aiming at this problem, this paper improved adaptive particle refinement (APR) technology by optimizing the interpolation

This paper proposes two different approaches for deriving the Vlasov-Navier–Stokes (or Vlasov-Stokes) system used in the theory of ‘thin’ aerosol flows from two kinds of microscopic models. One approach is based on homogenization techniques for elliptic equations in domains with holes, whereas the other approach is based on the various mathematical tools used to study the fluid dynamic limits of the

A computational study is conducted to systematically investigate the effect of rotating speed on vortex shedding characteristics and far-field wake patterns of an elliptic foil rotating in uniform cross flows at low Reynolds numbers. It is found that at low rotating speed, vortices shed at the advancing and retreating edges of the foil could form a strong vortex pair in the wake. At high rotating speed

Ultrasound contrast agents (UCA) have been widely used in ultrasonic medical applications. The dynamics of UCA should be simulated accurately to maximize the application effects. The acoustic radiation of UCA oscillations is affected by the liquid compressibility which has to be considered. This paper deduces a simple equation based on Keller-Miksis equation to describe the dynamics of UCA with a polymer

The fluid flow in a circular tube filled with a porous medium is important in packed-bed catalytic reactors. Due to gravity the fluid only partially fills the inclined tube. The Darcy–Brinkman equation is solved by two different highly efficient boundary collocation methods. The flow rate depends on the porous medium parameter which quantifies permeability and the level of fill of the fluid. It is

In this study, we built a series of roughness surfaces in an atmospheric boundary layer (ABL) wind tunnel with the aim of determining the characteristics of flow and surface pressure around a rough surface placed on a deep turbulent boundary layer. The ABL has a significant role in the exchange and transfer of momentum close to the wall. In particular, the roughness sublayer (RS), the lower part of

We investigated non-linear resonance of low- and high-frequency waves (LHFWs) in a cooled hypersonic boundary layer. First, an experimental campaign was conducted in the high-enthalpy shock tunnel at the Japan Aerospace Exploration Agency using a circular-cone model. The results allowed us to identify early-developing low-frequency waves and strong cross-bicoherence among LHFWs, indicating that non-linear

The compressible vortex ring emanating from an ultra-short driver section shock tube is simulated using Euler and Navier–Stokes solvers for a diaphragm pressure ratio of 8.4. The numerical results are compared with smoke flow visualization experiments performed in a shock tube. Here the main focus is to compare the vortex ring evolution during its self-sustained motion as many researchers studied the

The stability of the transient state of convection in an inclined fluid layer on heating one of the boundaries impulsively has been discussed. The closed form time dependent basic solutions for the velocity and the temperature are obtained. The non-linear stability of the transient state is investigated by using the energy method. The stability limit for the Rayleigh number Ra is found at different

Dynamic and thermal characteristics of a turbulent and heated offset jet were numerically investigated using Ansys Fluent. The jet’s heated bottom wall is mounted with a single square-section rib and characterized with constant heat flux. The flow velocity, at the nozzle exit, corresponds to a Re value of 39 000, besides the offset ratio is assumed to be fixed at 5. Nine different rib positions were

The hydrodynamic stability of an imploding cylindrical liquid liner is analytically and numerically investigated. Such dynamic system can be used to compress gas trapped by the liner, as one may seek in a hydrogen fusion reactor. For such system it is vital for the liner to stay intact at least up to the turnaround point, which marks the point of maximum compression of the inner gas. New two-dimensional

Complex ray theory successfully describes temporal and spatial development of a two-dimensional wave packet into steady and semi-infinite distribution of very large disturbances in the wake accompanied by a region of reverse flows. Final formation of the steady state is caused by the existence, on integral path of propagation equations, of a logarithmic singularity, at which the group velocity and

Viscous flow around two unequal cylinders is simulated by solving the non-dimensional Navier–Stokes equations. A total of 13 two-dimensional numerical cases are carried out in this study for the flow fields around two adjacent cylinders at Re = 200. The ratio of d / D is equal to 0.25 ( d and D are the diameters of the secondary and primary cylinders, respectively), the distance between two cylinders

Many chemical and biological systems have applications involving fluid–structure interaction (FSI) of flexible filaments in viscous fluid. The dynamics of single- and multiple-filament interaction are of interest to engineers and biologists working in the area of DNA fragmentation, protein synthesis, polymer segmentation, folding–unfolding analysis of natural and synthetic fibers, etc. To perform numerical

The interaction of a submerged shallow synthetic jet with a parallel free surface has gathered substantial interest, owing to its relevance to the operation of marine vehicles viz. ships that move close to the water surface. However, despite exhaustive research on the perturbation on a free surface, very few studies have experimentally investigated the effect of unconfined water surface height on the

Helical pipes have been widely applied in a vast range of industries owing to the remarkable characteristics. In practice, they still face the challenge of undesirable increased pressure resistance. The investigation on the flow characteristics in helix is essential to explore the pressure loss mechanism. In this paper, the k − ω model and k − ω SST model are utilized to investigate the flow characteristics

In this study, the ground effect over a wing without/with a flap at low Reynolds numbers was investigated experimentally. Three-dimensional flow fields over and behind a flapped wing and single (without flap) wing in/out of ground effect at several clearances and Re numbers (0.75 × 10 5 , 1 × 10 5 and 1.5 × 10 5 ) were investigated using three different experimental methods. From flow visualization

The structures of wing-tip vortices at a low Reynolds number ( ##IMG## [http://ej.iop.org/images/1873-7005/52/4/045503/fdrab9b63ieqn1.gif] {$Re_c = 10^3$} ) are studied by direct numerical simulation. After confirming the basic features of the wing-tip vortices, the distributions of axial vorticity and velocity are investigated in detail. The vorticity distribution consists of a dominant symmetric

The location and orientation effect of control plates (CP) in and around the flow separation region of a circular cylinder has been numerically investigated in the laminar flow regime at Reynolds number 100. The vortex shedding and convective heat transfer characteristics have been analysed for both upstream and downstream locations of the control plates using Ansys Fluent 18.0. The drag and lift coefficient

In this paper, instabilities and breakup phenomena of a viscous liquid column jet in an inviscid stationary surrounding gas are analytically investigated, when the jet flows through a coaxial cylindrical sheath. Under a long wave approximation, axisymmetric non-linear evolution equations of the jet and surrounding gas are derived and numerically solved under a spatially periodic boundary condition

In this paper, the vortex-induced vibration (VIV) of a main cylinder with two symmetrically arranged control rods at Reynolds number of 500 is numerically simulated. The control rods and the main cylinder are connected rigidly and can move synchronously, which is modeled as a spring oscillator with double degree of freedom. Seven gap ratios ( G/D = 0.1 ~2) and sixteen angles ( α = 15° ~165°) are used

Noether’s theorem reads: ‘A symmetry implies a conservation law’. From a single relativistic energy equation of fluid motion, two conservation equations are obtained in the non-relativistic limit: mass conservation and energy conservation of traditional form. We are concerned with the mass conservation equation and investigate what symmetry implies the mass conservation, and conversely what symmetry

Experimental work is reported for premixed flames propagating in tubes. The flames were ignited with a pilot flame and the flame propagation captured with high-speed cameras. Initial measurements were performed characterizing the rig. For downwardly propagating flames to a closed-end, methane and propane were studied. The flames initially propagated steadily, then at approximately a third of the way

The hydrodynamic instability of monochromatic inertia-gravity waves (IGWs) of finite amplitude, propagating at small angles either to the vertical or horizontal, is studied. In both cases, the corresponding angle serves as a small parameter in the problem, and instability is investigated using the Galerkin method. For IGWs that propagate at a small angle to the vertical, it is shown that stable density

This paper develops a simple model of the inertial range of turbulent flow, based on a cascade of vortical filaments. The filaments are taken to be helical, one turn of the helix playing the role of a turbulent eddy. A binary branching structure is proposed, involving the splitting of filaments at each step into pairs of daughter filaments with differing properties, in effect two distinct simultaneous

The Brinkman model is used to study the criterion of appearance of stationary convection in a porous horizontal layer saturated by a binary mixture of ferrofluids and heated from below. The analytical expression of the Rayleigh number is determined by dimensionless numbers for the combined effects of buoyancy and magnetic force on the one hand and magnetic force alone on the other. The effect of Darcy’s

In this paper, a second order model for Korteweg-type fluids is derived within the GENERIC formalism, whose standard application to Korteweg-type fluids is studied in detail in Part I of this series of papers. The higher-order model contains the second-order gradient of the density in the constitutive relation concerning internal energy, and the resulting Korteweg stress covers the original model proposed

This paper reports an experimental investigation of a vertical vortex advected over a rigid wall. The main goal is to study an unstationary, isolated structure, which reproduces a tornado-like flow in an hydraulic environment. The focus is set on the near-wall region, with two types of boundary condition: a smooth wall and a non-erodible sediment bed. Optical methods such as planar and stereoscopic

The influence of divergence schemes in typical turbulence modelling on the aerodynamic behaviours was investigated in this study. Four common divergence schemes have been used to predict the aerodynamic behaviours of a typical train in crosswinds, including the first order upwind differencing (UD), second order limited-linear differencing (LL), linear-upwind differencing (LU) and Linear-upwind stabilized

Gravitational settling of solid particles through density interfaces is studied numerically when at least one of the fluids is non-Newtonian. The Carreau–Yasuda model is used to model the shear-thinning behavior of the non-Newtonian fluid. The coupled level-set and volume-of-fluid method is used to track the interface between the two fluids. It is found that the presence of shear-thinning fluids significantly

This investigation addresses a systematic numerical method based on the finite volume method and a full multigrid technique to study two-dimensional and three-dimensional flow of an incompressible fluid inside a cavity driven by the motion of the upper lid. Quantitative aspects of two and three dimensional flows in lid-driven cavities are analyzed by encompassing descriptive Reynolds numbers Re bounded

A numerical simulation has been made of the combined stroke swimmer (a deformable sphere) and compared with the results of the second-order perturbation theory of Felderhof and Jones (2017). At a small ratio of the amplitude of the deformation of the sphere and the radius of the sphere the numerical and theoretical results agree well. However for a larger value of this ratio the results deviate due

Flow control devices are one of the most commonly studied fields of aerodynamic research in the world. This is because improvements in the aerodynamic performance of any vehicle lead directly to save fuel and money and reduce their operational costs. Another reason is that flow control can reduce the risk of aerial vehicles operating near complex structures which can generate high turbulence intensity

A computational study of three-dimensional instability of steady flows in a helical pipe of arbitrary curvature and torsion is carried out for the first time. The problem is formulated in Germano coordinates in two equivalent but different forms of the momentum equations so that results obtained using both formulations cross verify each other. An additional formulation in the cylindrical coordinates

The current experimental investigation was aimed at understanding the influence of reducing sections on the transient behavior of slug flow. Experiments were carried out using two concentric area cross-section reducers with 160 mm lengths; the first one was shaped as a conical frustum with a 44 mm inlet diameter reducing to a 30 mm outlet diameter and the second one as a frustum with the same inlet

Different concepts for controlling a non-slender delta wing are considered and compared with each other. The concepts are based on geometrical modifications of the leading edges. The strategy aims at producing an asymmetric distribution of lift due to vortices on the left and right wing half and thus, for example, rolling moments to be used in controlling the model. The effectiveness of different approaches

The current study deals the theoretical investigation of a viscous fluid due to metachronal waves of cilia through the curved channel with porous medium effects. Due to the complex nature of flow regime, curvilinear coordinates are used to develop constitutive equations for two-dimensional flow. Firstly, the whole system is transformed from fixed frame to wave frame of reference. Secondly, the scaling

In this paper, we propose a phase field method for the numerical simulations of a moving solid object in two-phase flows. A three-phase Cahn–Hilliard and Navier–Stokes model is employed for this problem. The solid region is represented by a single phase in the three-phase system. The rigidity constraint of the solid phase and the no-slip boundary condition on the solid-fluid interface is imposed by

The celebrated Poincaré (1910) steady solution, the uniform vorticity flow in a precessing spheroid, which is realized in the inviscid interior region outside the boundary layer in the strong spin and weak precession limit, is derived, as a unique solution analytically without any prior assumption on the spatial structure, and its singular behavior for a sphere is resolved. Assuming that the spin and