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