Speckle images have found multiple applications in image-based measurement techniques, where the objective of measurement is the estimation of speckle displacements between two often consecutive images. Depending on the characteristics of a measurement system and its measurands, the signal-to-noise ratio (SNR) of recorded images may become low and even marginal. One solution to improve the accuracy

To identify laminar/turbulent transition paths in plane Couette flow, a variational formulation incorporating a restricted nonlinear (RNL) system that retains a single streamwise Fourier mode, is used. Considering the flow geometry originally used by Monokrousos et al. (2011) and Duguet et al. (2013) and the same Reynolds numbers (Re), we show that initial perturbations obtained by RNL optimizations

The Lattice Boltzmann Method (LBM) was implemented to simulate the two-dimensional (2-D) Rayleigh–Taylor instability (RTI) during the mixing of the immiscible fluids. Two important parameters of the density and the viscosity as represented respectively by the Atwood and the Reynolds numbers were considered. In the calculation the density of two immiscible fluids was calculated by using the equation

A kinetic-theory based approach known as the lattice Boltzmann method (LBM) with multiple-relaxation-time (MRT) collision is employed to assess the non-Newtonian fluid models for standard two-dimensional benchmarks flow configurations. A two-dimensional nine-velocity square lattice (D2Q9) is used as a basic space-microscopic-velocity coupled LBM structure. The MRT-LBM formulation for the non-Newtonian

A lid-driven cavity flow of kaolinite suspension is investigated using a numerical approach. The suspension with a kaolinite concentration in the range of 15–28.5wt% is modeled using Bingham–Papanastasiou approach. The cavity is of a rectangular shape and has different aspect (height-to-width) ratios, that is, 0.5 (shallow cavity), 1 (square cavity), and 2 (deep cavity). The width-based Reynolds number

The present paper investigates numerically the hydrodynamic instabilities occurring in a cylindrical container filled with a conducting viscous fluid and submitted to an axial magnetic field. The axisymmetric swirling flow produced by rotation of the bottom disk, in which a vortex breakdown bubble occurred on the axis of symmetry. This flow structure represents one of the most important instabilities

Turbulence modeling plays a crucial role in simulating unsteady characteristics of cavitation flows. Owing to the different theoretical backgrounds of partially averaged Navier–Stokes (PANS) and filter-based models (FBMs), the differences in their unsteady cavitation flow predictions are worth comparing. In this study, PANS and FBM were used to predict the cloud cavitation regime around a three-dimensional

Rayleigh–Taylor instability (RTI) is a common phenomenon in daily life and in industrial application. Despite the long history of investigating the RTI with periodic boundary condition, there are only few studies for the RTI with no-slip side wall boundary condition. In fact, the RTI with the side wall boundary condition is more realistic physics. In this work, we investigate the side wall boundary

The near-field flow characteristics and jet fluid dispersion properties of non-oscillating and transversely oscillating jets issued from a fluidic oscillator were studied experimentally. A V-shaped fluidic oscillator was designed to induce transverse jet oscillations by merging two bifurcated alternatively issuing side jets. The characteristic flow patterns, evolution processes, velocities, vorticities

The wake dynamics behind a sinusoidally pitching custom designed symmetrical airfoil is analyzed computationally. The effect of pitching frequency and pitching amplitude is investigated independently at a constant Reynolds number. The wake patterns are found to exhibit a transition from von Karman to reverse von Karman vortex street and from symmetric reverse von Karman vortex street to asymmetric

This work focuses on the study of the phenomenon of vortex-induced vibrations in overhead lines under the effect of weak winds. Full three-dimensional simulation is not feasible because of the high length to width aspect ratios of the overhead lines. Thus a quasi-3D method based on strip theory is adopted in this work. This method decouples the system of interactions between the overhead line and the

George Santayana’s aphorism “Those who cannot remember the past are condemned to repeat it” has never been more apposite than as applied to this paper. The paper rebutted here reproduces, without any form of acknowledgement, the method of reproducing characteristics of the atmospheric boundary layer (ABL) in a wind tunnel published in 1957 (Owen and Zienkiewicz, 1957). This method, together with the

Submerged gas jet is commonly encountered in underwater cutting, underwater jet-propulsion, liquid metal mixing and other applications. In this paper the transient dynamics for the high-speed submerged gas jet in a flowing water environment was investigated. The experiments were carried out in an open water tunnel which could achieve high degassing rate. The jetting flow rate was varied from subsonic

The problem of an axisymmetric translational motion of an incompressible microstretch fluid past an immiscible stationary microstretch droplet in the presence of a uniform magnetic field is investigated. The inertial terms in the equations of motion are neglected, therefore the microstretch scalar function is uncoupled from the stream function and microrotation component. Analytical solutions are obtained

Thermal characteristics of time-periodic electroosmotic flow are analyzed in a micro-annulus under the influence of various alternating electric fields. Representative hydrodynamic and thermal quantities, i.e. volumetric flow rate and Nusselt number, demonstrate oscillatory behaviors approaching a quasi-steady state if few periods of time elapse. An important parameter named dimensionless frequency

The present paper is an extension of the work done by Fang and Tao (2012) in the presence of a magnetic field. The external magnetic field is applied normal to a stretchable disk surface and heat is transferred from the disk surface to the ambient fluid which gives a new family of unsteady viscous flow over a stretchable rotating disk with deceleration. The Navier–Stokes equations and the energy equation

Viscous/inviscid interaction methods employing velocity decomposition have been explored for reducing computational costs in external flow problems. For this, viscous simulations are made in reduced computational domains encompassing the rotational flow region. The coupling of potential and viscous solutions is made on a boundary of negligible vorticity, assessed by means of sampling lines normal to

Vortex-induced vibration (VIV) of an elastically supported disk is investigated computationally using large-eddy-simulation (LES). The disk motion is constrained to move in the transverse plane vertical to the free stream. Two sets of simulations are conducted at Re=165 and 210 over the reduced velocity range 3≤UR≤7.5 respectively. The disk shows a highly periodic large-amplitude vortex-induced vibration

The motion of the solid particles in the enclosed cavity is important, to investigate the interaction between the motion of the solid particles and the fluid flow, the motion of a neutrally buoyant elliptical particle in a lid-driven square cavity is studied with the lattice Boltzmann method. To understand, predict and control the motion of the elliptical particle, the effects of the aspect ratio,

This work endeavours to study the problem of axisymmetric oblique stagnation point flow above a rotating disc. An external flow impinges obliquely on a disc when the disc is rotating with constant angular velocity. Suitable similarity variables are introduced, for the first time, to transform the governing Navier–Stokes equations into a highly nonlinear system of ordinary differential equations, governed

The applications of freely falling bodies in steady water or air have been widely observed in nature, from the dispersing of a tree seed to the re-entry of a space shuttle. Disparate objects exhibit particular falling styles which have been studied for a long time. However, the mechanism behind this extensive phenomenon has not been clearly understood. In this paper, we investigate experimentally the

In this paper, we study the stability of a barotropic polar vortex cap on a rotating sphere. We present the linear stability analysis of the polar vortex cap, approximating the piecewise-continuous vorticity distribution by zonal bands of uniform vorticity. We investigate the dependence of the flow stability on the location of the vortex cap, modes of perturbation and rotation speed. The linear stability

A deformity of magnetic field discloses that different particle of ferrofluid exhibits different pattern to accumulate more closely with strong magnetic properties; this is because of the existence of a homogeneous ferromagnetic liquid. In this context, the Newtonian fluid (ordinary liquid) is magnetized by dispersing into porous media. A mathematical model for ferromagnetic fluid is developed by means

The swimming of a deformable uniform sphere is studied in second order perturbation theory in the amplitude of the stroke. The effect of the first order reaction force on the first order center of mass velocity is calculated in linear response theory by use of Newton’s equation of motion. The response is characterized by a dipolar admittance, which is shown to be proportional to the translational admittance

The laminar–turbulence transition phenomenon widely exists on the surface of many energy equipment, which is deserved to be studied because of the complex mechanics and some induced undesirable consequences. The goal of present work is to investigate the transitional flows around the forward and reversed hydrofoils at different incidences using the SST γ-Re˜θt transition model, with special emphasis

In this paper, the geometric models of microfluidics NON-AND and AND-OR droplet logic gate devices are designed, and the operations of NON-AND and AND-OR logic are implemented in the designed models. Based on the color-gradient model (R-K model) of lattice Boltzmann method (LBM), the two-phase flow pattern in microchannel is simulated. Based on the “equivalent length method”, the Laplace resistance

This paper experimentally examined a feedback-loop mechanism generating tonal noise when a two-dimensional (2-D) protuberance as high as the boundary-layer thickness was placed in zero- and weak adverse-pressure-gradient laminar boundary layers. Onset of tonal noise required rapid disturbance growth due to strong instability in a small separation bubble formed just upstream of the protuberance, in

A plate is immersed in a conducting flow with parallel velocity and magnetic field. The fluid is assumed inviscid and weakly diffusive. A perturbation is created in the plate, which in its turn modifies the background flow by generating a boundary layer. When the perturbation is variable in time, the layer is shown to possess a complex inner structure. The perturbed quantities decrease exponentially

In a recently published work (Sheng, 2020), Sheng identified inconsistencies in the concepts and principles leading to the Navier–Stokes equations and proposed a new asymmetric “friction tensor” to resolve these inconsistencies. We show that this friction tensor can be interpreted as the non-isotropic part of a vorticity-influenced viscous stress tensor following the analysis in Berdahl and Strang

The Green-function and boundary-element method, widely used in ship and offshore hydrodynamics, requires accurate and efficient numerical evaluation of flows created by (typically polynomial) distributions of singularities (sources and dipoles) over (flat or curved) panels of various shapes (notably quadrilateral or triangular) that approximate the surface of a ship or offshore structure. This crucial

In the actual working condition, the cavitation phenomenon is inevitably accompanied by the collapse of a large number of bubbles, and will affect the performance of hydraulic machinery. Therefore, it is of great significance to study the process of multi-bubble collapse. The double bubble system is the most simplified one in multi-bubble system, and it is also the basis of studying multi-bubble. However

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 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

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

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

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

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

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 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

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

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 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

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

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

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

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

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

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