A wide range of natural and industrial processes, such as a droplet falling in the ocean as well as the injection of fuel in an internal combustion engine, are physically explained by the study of multiphase flows. The understanding of these processes is a fundamental step in order to optimize their use in industrial applications. Computational tools have been increasingly used for that purpose. This

This study focused on Cu-Al2O3/water hybrid nanofluid to address the issue related to mixed convection stagnation-point flow and heat transfer over a permeable stretching/shrinking sheet with the magnetic field and heat source/sink effects. The governing equations of the problem are initially reduced into similarity equations by utilizing similarity transformations, prior to being solved numerically

A series of 8 laboratory experiments was used to investigate the dynamics of a few almost neutrally-buoyant finite-size particles in the entire volume of a rectangular tank open to air and filled with water. Stirring was achieved by a cylinder executing a two-dimensional periodic Lissajoux figure. The rate and direction of stirring by the cylinder was varied. The particle motions were analyzed using

We consider a high-Reynolds-number Boussinesq gravity current (GC) propagating in a channel above a permeable horizontal boundary. The current (of reduced gravity g′) is released from a rectangular lock (of length x0 and height h0), and after an adjustment (slumping) stage is expected to enter into a similarity stage, on which we focus here, using a thin-layer shallow-water model. The classical analytical

The longwave oscillatory Marangoni convection in a horizontal two-layer film heated from above, in the presence of an interfacial heat consumption, is considered. The effect of gravity is taken into account. The action of a time-periodic parameter modulation on the nonlinear Marangoni waves is investigated. The problem is studied numerically in the framework of longwave amplitude equations. The alternating

Large eddy simulation (LES) with dynamic Smagorinsky model (DSM) has been implemented to elicit the turbulence characteristic of the flow inside a cubic lid-driven cavity at Reynolds number of 10000. The coherent organized structures tear, pair and disintegrate leading to the evolution of turbulence. They are reflected in the RMS (root mean square) plots of the turbulent fluctuations in different planes

For univentricular heart patients, the Fontan operation creates a unique non-physiologic circulation where the pulmonary arteries are directly supplied from the systemic venous blood return, leading to chronic non-pulsatile low-shear-rate pulmonary blood flow. Computational fluid dynamic (CFD) simulations are widely used in cardiovascular biofluid studies and a Newtonian fluid assumption is common

The classical Merkin and Needham’s wall-jet problem was studied for copper-titanium dioxide/water hybrid nanofluid with the effects of suction/injection and thermal energy. The governing equations were converted into non-linear ordinary differential equations by using proper similarity transformations. These equations were then solved analytically for the hybrid nanofluid flow and temperature distribution

The 3D frequency-domain analysis of the flow around a ship advancing in regular waves, in deep water, via the Green-function and boundary-integral method requires a practical and reliable way of evaluating the flow due to an arbitrary distribution of singularities (sources and dipoles) over the (flat or curved, quadrilateral or triangular) panels that are commonly used to approximate a ship hull-surface

In the nature, the fish can control the wave propagation on the caudal fin using the sarcomere at the leading edge of the caudal fin. The control methods can be classified into three modes: Active Heave and Active Pitch (AHAP),Passive Heave and Active Pitch (PHAP), Active Heave and Passive Pitch (AHPP). Which mode can produce the largest thrust? Which mode can develop the most efficient swimming performance

In the article we consider the flow of viscous compressible fluid in a channel with oscillating walls. The obtained solutions of linearized Navier–Stokes equations suggest that resonance phenomena are possible under certain conditions, namely, under the particular relation between the frequency of wall vibration, the geometrical characteristics of a channel and speed of sound in the fluid. Resonance

If no filter is applied, steep short waves appear at the waterline of a ship – in the vicinity of the fore shoulder – at Froude numbers smaller than about 0.35. These short waves are shown to correspond to the divergent waves created by the ship bow. A practical method for effectively filtering steep short shoulder and midship waves, which are inconsequential and likely unrealistic, is given. This

In 1957, Crapper found an exact solution for capillary waves in an irrotational flow of infinite depth. Here we provide asymptotic and numerical evidence that a Crapper wave makes the profile of a periodic traveling wave in a constant vorticity flow when the effects of gravity and surface tension are negligible. This is achieved by explicitly constructing successive approximate solutions for small

A two-dimensional viscous flow in a rough curved channel is investigated. The roughness are considered to be sinusoidal corrugations. The asymptotic solution is obtained using boundary perturbation technique for small amplitude of the corrugations. It is found that, for any radius of curvature, the flow rate is invariably decreased by the corrugations. The effect of corrugations on the flow rate increases

Unsteady flow through a curved channel with roughness in the form of sinusoidal corrugations is examined. The flow is generated by a time periodic pressure gradient. The fluid velocity is both time and space periodic, as a result of the oscillatory pressure gradient and the geometry of the curved channel. The effects of the inherent parameters; physical and geometrical, on the velocity field and the

Linear and weakly nonlinear stability analyses of Brinkman–Bénard convection in water with a dilute concentration of single-walled carbon nanotubes (SWCNTs) is studied analytically in the paper. The thermophysical properties of water-SWCNTs nanoliquid and water-SWCNTs nanoliquid-saturated high-porosity medium are calculated using phenomenological relations and the mixture theory. The five-mode Lorenz

The present article experimentally and theoretically probes the evaporation kinetics of sessile saline droplets. Observations reveal that presence of solvated ions leads to modulated evaporation kinetics, which is further a function of surface wettability. On hydrophilic surfaces, increasing salt concentration leads to enhanced evaporation rates, whereas on superhydrophobic surfaces, it first enhances

In this paper we provide a FFT algorithm to compute the effective permeability of doubly porous solids constituted of two populations of pores which are different in size. The paper focuses on the resolution of the fluid flow at the intermediate scale, that of the macropores, that requires the resolution of the coupled Darcy/Stokes problem. The permeability associated with the first population of cavities

The low-Reynolds-number flow past a sphere moving near a right dihedral corner made by a stationary and a tangentially sliding wall is considered. Using the superposition principle, the arbitrary motion of the sphere is decomposed into simple elementary motions. Fully-resolved spectral-element simulations are carried out in the frame of reference translating and rotating with the particle such that

The aim of this work is to perform a numerical simulation of the turbulent flow in an eccentric channel for a Reynolds number ReDh = 7300. The Reynolds number is based on the bulk velocity, UBulk, the hydraulic-diameter, Dh, and the kinematic viscosity, ν. To achieve this goal, a hybrid RANS/LES turbulence model called DES-SST is used. In this formulation, special functions are computed to convert

The behaviour of aluminium spherical particles of density ρp=2700 Kg/m3 dispersed in a turbulent round water jet, at Reynolds number Re≈15000 and exit Stokes number St0=0.013 is investigated via Particle Image Velocimetry up to x∕D=16 from the nozzle exit. Average and fluctuating velocity fields are analysed and compared to the unladen jet condition. Generally, particles are reported not to behave

The fluid mechanics problem of an initially spherical compound drop suspended in another fluid undergoing a nonlinear extensional creeping flow, is the subject of this theoretical report. The compound drop is originally composed from an inner spherical drop positioned at the center of a spherical fluid shell. The problem is governed by six dimensionless parameters: the external capillary number (Ca)

The aim of the present work is to control the dynamic stall of a pitching NACA0012 airfoil and improve its aerodynamic performance by using a synthetic jet in a low Reynolds number compressible flow for use in prospective applications, such as flights on Mars and in the stratosphere. A recently developed variable correction-based immersed boundary method is employed to predict the complex flow fields

We provide a thermodynamic framework for binary mixtures of Korteweg fluids with two velocities and two temperatures. The constitutive functions are allowed to depend on the diffusion velocity and the specific internal energy of both constituents, together with their first gradients, as well as on the mass density of the mixture and the concentration of one of the constituents, the latters together

Periodical dynamic characteristics induced by geometric parameters and operational variables of the self-excited pulsed cavitation jet under the optimum experimental condition is analyzed in the present study. The mechanism of cavitation jet occurrence is interpreted by combining the jet shape, the striking force, and the cavity pressure. With the increase of the inlet pressure, the pulsed frequency

When the vortices shedding from an upstream rod impinge upon the surface of a downstream airfoil, the resultant vortex–body interaction noise can be significant. The use of “natural rod-base blowing” to reduce this interaction noise is investigated numerically using a 3D hybrid computational aeroacoustics approach. The natural blowing is generated through an internal slot that interconnects the stagnation

A systematic study on targeted drug delivery is carried out in an unsteady flow of blood infused with magnetic nanoparticles with an aim to understand the flow pattern and nanoparticle aggregation in a diseased arterial segment having atherosclerosis. The magnetic NPs(nanoparticles) are supervised by a magnetic field, which is significant for the therapeutic treatment of arterial diseases, tumors,

The Green function representing the potential flow generated by a source with unit strength advancing beneath an ice cover along a straight path at a constant speed is studied in the paper. The ice is modelled as elastic plate. The Green function satisfying the linearized covered-surface condition is derived and expressed in the form of a double Fourier integral with respect to wavenumber k and polar

Diffraction-radiation of regular waves by offshore structures and flows around ships advancing in calm water or in regular waves are commonly analyzed via potential-flow methods based on the Green functions that satisfy the corresponding free-surface boundary conditions. This realistic, practical, and widely-used approach requires evaluation of free-surface flows due to arbitrary (notably constant

The acoustic spectrum of a gas-filled resonating cavity can be used to indirectly probe its internal velocity field. This unconventional velocimetry method is particularly interesting for opaque fluid or rapidly rotating flows, which cannot be imaged with standard methods. This requires to (i) identify a large enough number of acoustic modes, (ii) accurately measure their frequencies, and (iii) compare

Two-dimensional uniform vortices that rotate without deforming in an isochoric, inviscid fluid are investigated. They have polygonal symmetry and are usually considered of the same kind of the famous Kirchhoff elliptical one. By following this idea, their shapes and rotation speeds are calculated through a new integral approach. It is heuristically proved, by examining the co-rotating streamlines,

The Fontan procedure for univentricular heart defects creates a unique circulation where all pulmonary blood flow is passively supplied directly from systemic veins. Computational simulations, aimed at optimizing the surgery, have assumed blood to be a Newtonian fluid without evaluating the potential error introduced by this assumption. We compared flow behavior between a non-Newtonian blood analog

Shockwave lithotripsy repeatedly focuses shockwaves on kidney stones to induce their fracture, partially through cavitation erosion. A typical side effect of the procedure is hemorrhage, which is potentially the result of the growth and collapse of bubbles inside blood vessels. To identify the mechanisms by which shock-induced collapse could lead to the onset of injury, we study an idealized problem

We study the formation of the mitral vortex ring during early diastolic filling in a patient-specific left ventricle using direct numerical simulation. The geometry of the left ventricle is reconstructed from Magnetic Resonance Imaging (MRI). The heart wall motion is modeled by a cell-based activation methodology, which yields physiologic kinematics with heart rate equal to 52 beats per minute. We

Recent experiments have shown that rapid kinematic mixing occurs in the pulmonary alveoli. Here the Reynolds number is very small, there is recirculation in the alveolar cavity and the alveolar walls move periodically. We have recently shown that non-diffusing particles move chaotically in a two-dimensional model flow with the above features. In parts of the lung, however, there is asynchrony between