Nonlinear evolution equations, correct up to fourth order in wave steepness, are derived for a pair of obliquely interacting wave packets in the presence of a thin pycnocline. These evolution equations are then employed to perform stability analysis of a pair of obliquely interacting uniform wave trains. Figures plotted here reveal that the growth rate of instability decreases with the increase in

This work studied the capability of a commercial CFD code in modelling two-phase flow from a header through two branches. The geometry considered in this study consists of a rectangular tank with two horizontal outlet branches of the same diameter d=6.35 mm, separated by a distance L centre to centre L∕d=1.5 with their centrelines falling in a plane inclined an angle θ = 30° from the horizontal. A

In immiscible liquid–liquid Newtonian flow through a porous medium, one phase often becomes trapped in corners or narrow regions by capillary forces as blobs (e.g. oil ganglia) deep within the matrix, whilst the second flow exhibits a steady and laminar flow (e.g. of water) that has negligible influence on the trapped liquid–liquid interfaces. However, recent microfluidic experiments have shown the

This manuscript scrutinizes the (2+1)-dimensions chiral nonlinear Schrödinger’s equation with constant coefficients by utilizing two creative mix strategies. The creative mix strategies are namely the functional variable method and first integral method. Solution and singular soliton solutions are successfully recovered through integration techniques. The intermittent particular arrangements have been

The bird strike incident is a hazard that affects the structural integrity of the aircraft. Bird strikes cause a surge on the wing profile affecting the aerodynamic performances and flight safety of the aircraft. Flight authorities enforce the manufacturers to perform numerous tests before the aircraft are available in the aviation market. Numerical studies and bird strike simulations have become an

In order to identify transitional flow, the linear stability of inward flow in a narrow gap between co-rotating disks is studied. Two methods are developed. The local approach assumes periodic nature of the flow in radial and circumferential direction, whereas the computationally more expensive biglobal variant only requires periodicity in circumferential direction. Stability maps are provided for

The paper presents an extension of the diagnostic-plot scaling (Alfredsson et al., 2012) of the turbulence-intensity profiles for the outer region of adverse-pressure-gradient (APG) turbulent boundary layers (TBLs). An extended formula including the shape factor is proposed, which allows the diagnostic-plot scaling to be used in strong APGs at high Reynolds numbers. The validity of the new formulation

The Reynolds decomposition is used to derive a new set of mean-flow equations for linear viscous fluids, with low compressibility (fluids in the liquid state). Additional shear and normal stresses are related to the velocity turbulent fluctuations in order to interpret the considerable energy dissipation in processes which are accompanied by rapid changes in liquid density, at least within the frame

This paper discusses the momentum jump condition across a viscous interface, which shows Newtonian behavior, i.e., is a Boussinesq surface fluid, by reviewing and expanding the works of Edwards et al. (1991) and Slattery et al. (2007). The necessary geometrical/mathematical tools for the derivation of the jump condition, and the jump condition itself are systematically derived for different cases defined

The hydro-elastic response of incident wave with a horizontal floating ice-floe on a sea is studied by using linear potential theory. The lower side of the sea is bounded by an adaptable layer with small base distortion. Here, the ice-floe and adaptable bottom surface are modeled as lean uniform elastic plates. In such circumstances, there are two types of time-harmonic proliferating waves that exist

In this study, the instability behavior of a confined non-Newtonian liquid jet in an annular gas layer is investigated theoretically. The viscosity of the non-Newtonian liquid is described using the power law model, and the corresponding dispersion relation is obtained by conducting a linear stability analysis. Additionally, the effects of heat and mass transfer, gas-to-liquid axial velocity ratio

The dynamic characteristics of droplet obliquely impact on a liquid film are investigated numerically by using the Coupled Level Set and Volume of Fluid method (CLSVOF), with the impact angle ranging from 0°to 60°. The influence factors as film thickness and Weber number on the splashing formation and the crown evolution are also systematically investigated. Results showed that the crown radius on

Understanding granular flows past an obstacle is very important to most possibly avoid damage to human properties and infrastructures. The present paper investigates the influence of an obstacle on dry and fluid-saturated granular flows to gain insights into physics behind them. To this end, we extend the existing depth-integrated theory by considering additional effects from the pore fluid pressure

A model for the wave motion of an internal wave in the presence of current in the case of intermediate long wave approximation is studied. The lower layer is considerably deeper, with a higher density than the upper layer. The flat surface approximation is assumed. The fluids are incompressible and inviscid. The model equations are obtained from the Hamiltonian formulation of the dynamics in the presence

The current study evaluates the effect of taking into account the second order term of the Rayleigh–Plesset equation for the numerical simulation of cavitation with homogeneous mixture models. For that, the corrected expression for the condensation mass transfer rate has been mathematically derived and implemented in the original Zwart and Singhal cavitation models. Two tests cases of steady sheet

In the present contribution, we analyze the non-stationary, incompressible, laminar, natural convection flow in a rectangular enclosure filled with a micropolar-nanofluid (Al2O3/water) in the presence of a magnetic field, using Dynamic Mode Decomposition (DMD) and Proper Orthogonal Decomposition (POD) method. DMD method utilizes numerically or experimentally obtained data (often generated by nonlinear

In this paper, we used the Hirota bilinear method for investigating the third-order evolution equation to determine the soliton-type solutions. We probe five cases including lump, lump–kink called the interaction between a lump and one line soliton, lump-soliton called the interaction between a lump and two-line solitons, kinky breather–soliton and finally the stripe soliton function only with exponential

An elegant four-dimensional Lorentz-invariant first-integral of the energy–momentum equations for viscous flow, comprised of a single tensor equation, is derived assuming a flat space–time and that the energy–momentum tensor is symmetric. It represents a generalisation of corresponding Galilei-invariant theory associated with the classical incompressible Navier–Stokes equations, with the key features

A hydrodynamic model, with incorporation of porosity, is considered to investigate oblique water wave scattering by two fully submerged parallel porous plates with the wave propagating over a porous bed in a homogeneous fluid flow with the upper surface exposed to atmosphere. The porous plates are assumed to follow the theory of thin plates and the wave propagation through the porous structure follows

This study aims to investigate the evolution of transient force and energy features in a thermo-sensitive cavitating flow around a hydrofoil. A cavitation model is extended to investigate the thermal effect, and a shear stress transfer — partially averaged Navier–Stokes turbulence model is adopted to simulate the cavitating turbulent flow. The distribution of changed cavitation number is consistent

In this paper, numerical analysis is conducted using a local camber correction approach called “decambering” to predict pre and post-stall aerodynamic characteristics of multiple lifting surfaces operating in formation. A three wings Chevron formation and five and nine wings V-formation are studied. NACA2412 wing section is used and experimental validation is provided with Cessna 172 aircrafts flying

This paper characterizes the hydrodynamics of laminar flows through circular ducts equipped with plain square woven meshes/screens in their role as static mixers. The CFD model was used to investigate the effect of screen geometry, number of screens, inter-screen spacing, and operating conditions on the velocity and pressure fields. This work therefore presents an analysis of the velocity contours

A spatiotemporal analysis is performed for an incompressible and inviscid compound jet moving in an unbounded inviscid static medium in this article. A detailed parametric study is carried out to explore the transition from absolute to convective instability for different operating conditions. The absolute and convective regions are shown through four plots: (i) inner density ratio (Qi) and Weber number

This paper presents a three-dimensional nonhydrostatic model to solve the Navier–Stokes equations using an unstructured finite volume method. The physical domain could be geometrically arbitrary. To avoid the checkerboard problem caused by non-staggered grids, a momentum interpolation method is used by introducing face-normal velocities at the mid-points of the cell faces. As the Large Eddy Simulation

This article enlightens on the hydrothermal performance of radiative nanofluid flow over a curved stretched surface. The curved surface is coiled inside a circular segment of radius R. The surface has been presumed to be permeable and slippery. Effects of multiple convective conditions i.e. convective conditions at the surface caused by both heat and mass transport are incorporated to explore the outcomes

The flow through partially-open control valves in navigation locks, particularly at the early portion of an operation cycle, is characterized by high velocities, flow recirculation, significant pressure drops, and pressure fluctuations within the culverts. Optimizing the flow control system is a key point in hydraulic projects of high-drop locks. In order to analyze the hydraulic parameters of the

The investigation on the flow of non-Newtonian (Casson) fluid is made between parallel discs, executing in-plane motion in different manners. The fluid motion is induced due to upper radially stretching or shrinking disc at the rate a and lower rotating disc at an angular velocity Ω, with plate separation h. The nondimensional Navier–Stokes (NS) equations are reduced to coupled ordinary differential

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 utilising 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 analysed using

We consider a high-Reynolds-number Boussinesq gravity current 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