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

Univentricular heart disease is the leading cause of death from any birth defect in the first year of life. Typically, patients have to undergo three open heart surgical procedures within the first few years of their lives to eventually directly connect the superior and inferior vena cavae to the left and right pulmonary arteries forming the Total Cavopulmonary Connection or TCPC. The end result is

Knowledge of the response of elastic capsules to imposed fluid flow is necessary for predicting deformation and motion of biological cells and synthetic capsules in microfluidic devices and in the microcirculation. Capsules have been studied in shear, planar extensional, and axisymmetric extensional flows. Here, the flow gradient matrix of a general irrotational linear flow is characterized by two

An analysis is made of the fluid-structure interactions necessary to support self-sustained oscillations of a single-mass mechanical model of the vocal folds subject to a nominally steady subglottal overpressure. The single-mass model of Fant and Flanagan is re-examined and an analytical representation of vortex shedding during 'voiced speech' is proposed that promotes cooperative, periodic excitation