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Purpose: Scientists have been conducting trials to find ways to reduce fuel consumption and enhance heat transfer rates to make heating systems more efficient and cheaper. Adding solid nanoparticles to conventional liquids may greatly improve their thermal conductivity, according to the available evidence. This study aims to examine the influence of external magnetic flux on the flow of a mixed convective Maxwell hybrid non-Newtonian nanofluid over a linearly extending porous flat plate. The investigation considers the effects of thermal radiation, Dufour and Soret. Design/methodology/approach: The mathematical model is formulated based on the fundamental assumptions of mass, energy and momentum conservation. The implicit models are epitomized by a set of interconnected nonlinear partial differential equations, which include a suitable and comparable adjustment. The numerical solution to these equations is assessed for approximate convergence by the Runge−Kutta−Fehlberg method based on the shooting technique embedded with the MATLAB software. Findings: The findings are presented through graphical representations, offering a visual exploration of the effects of various dynamic parameters on the flow field. These parameters encompass a wide range of factors, including radiation, thermal and Brownian diffusion parameters, Eckert, Lewis and Soret numbers, magnetic parameters, Maxwell fluid parameters, Darcy numbers, thermal and solutal buoyancy factors, Dufour and Prandtl numbers. Notably, the authors observed that nanoparticles with a spherical shape exerted a significant influence on the stream function, highlighting the importance of nanoparticle geometry in fluid dynamics. Furthermore, the analysis revealed that temperature profiles of nanomaterials were notably affected by their shape factor, while concentration profiles exhibited an opposite trend, providing valuable insights into the behavior of nanofluids in porous media. Originality/value: A distinctive aspect of the research lies in its novel exploration of the impact of external magnetic flux on the flow of a mixed convective Maxwell hybrid non-Newtonian nanofluid over a linearly extending porous flat plate. By considering variables such as solar radiation, external magnetic flux, thermal and Brownian diffusion parameters and nanoparticle shape factor, the authors ventured into uncharted territory within the realm of fluid dynamics. These variables, despite their significant relevance, have not been extensively studied in previous research, thus underscoring the originality and value of the authors' contribution to the field. [ABSTRACT FROM AUTHOR]

Coiscéim, an Irish-language publishing house founded by Pádraig Ó Snodaigh over forty years ago, has produced more than 1,500 titles. To honor Ó Snodaigh's contributions to literature, four Coiscéim poets describe their recent collections. The collections explore themes of fragility, loss, displacement, love, and the human experience. They delve into emotions such as sadness, joy, anger, and hope, while also examining the nature of human relationships and the self. The collections use various organizing principles, including contemplation, accountancy, and folklore, to address existential concerns, survival, and the impact of external factors on individuals. [Extracted from the article]

A high-order flux reconstruction solver has been developed and validated to perform implicit large-eddy simulations of industrially representative turbomachinery flows. The T106c low-pressure turbine and VKI LS89 high-pressure turbine cases are studied. The solver uses the Rusanov Riemann solver to compute the inviscid fluxes on the wall boundaries, and HLLC or Roe to evaluate inviscid fluxes for internal faces. The impact of Riemann solvers is demonstrated in terms of accuracy and non-linear stability for turbomachinery flows. It is found that HLLC is more robust than Roe, but both Riemann solvers produce very similar results if stable solutions can be obtained. For non-linear stabilization, a local modal filter, which combines a smooth indicator and a modal filter, is used to stabilize the solution. This approach requires a tuning parameter for the smoothness criterion. Detailed analysis has been provided to guide the selection of a suitable value for different spatial orders of accuracy. This local modal filter is also compared with the recent positivity-preserving entropy filter in terms of accuracy and stability for the LS89 turbine case. The entropy filter could stabilize the computation but is more dissipative than the local modal filter. Regarding the spanwise spacing of the grid, the case of the LS89 turbine shows that a z + of approximately 45 − 60 is suitable for obtaining a satisfactory prediction of the heat transfer coefficient of the mean flow. This would allow for a coarse grid spacing in the spanwise direction and a cost-effective ILES aerothermal simulation for turbomachinery flows. [Display omitted] • Effect of Riemann solvers is studied for turbomachinery ILES simulations with FR. • Modal filtering with a smoothness indicator is used to stabilize the FR computation. • The positivity preserving entropy filter is assessed for turbomachinery ILES. • Coarser spanwise grid can be used to predict satisfactory mean flow quantities. [ABSTRACT FROM AUTHOR]

A clinical trial is currently underway to evaluate the effects of a device called Sustained Acoustic Medicine (SAM) on circulation. The trial is in the interventional phase and is designed as a randomized study. The primary outcome measures include blood flow and temperature measurements. The SAM device emits continuous ultrasound at a specific frequency and intensity. The trial is set to be completed by September 30, 2024. The study is being conducted in the United States and is led by George K Lewis from ZetrOZ Systems LLC. The recruitment for the study is not yet open, but the eligibility criteria include being a healthy volunteer between the ages of 18 and 50. The text also mentions different study arms involving the SAM device and diclofenac patches. The SAM device is also referred to by other names such as Wearable Ultrasound Device and Long Duration Ultrasound. [Extracted from the article]

A recent study conducted by researchers at the University of Iowa explores the development of renal tubules in the postnatal period and its importance for adult kidney function. The study suggests that changes in fluid shear stress and stretch on immature renal tubules play a role in their differentiation and proliferation. The researchers also found that kidney organoids under flow have better development of tubular structures and the expression of cilia and solute transporters. Understanding how tubular flow and ion fluxes regulate renal tubule development may lead to improved treatments for congenital renal tubulopathies. [Extracted from the article]

EMD Millipore Corporation has been issued a patent for compact spiral-wound filter elements, modules, and systems. The patent describes improved spiral-wound filter elements that provide the performance attributes of cassette filters. These filter elements achieve permeate fluxes similar to cassette filters without the need for compression holder assemblies. The invention also includes a tangential flow filtration (TFF) system that incorporates the spiral-wound filter elements. The patent provides a method for filtering a liquid feed using the filter elements and describes a process for producing a high turbulence-promoting feed screen. The spiral-wound filter elements offer an alternative to cassette filters, providing compactness and ease of use. [Extracted from the article]

The article offers step-by-step instructions for creating a sprigged jars.

Purpose: Accurate prediction of temperature and heat is crucial for the design of various nano/micro devices in engineering. Recently, investigation has been carried out for calculating the heat flux of gas flow using the concept of sliding friction because of the slip velocity at the surface. The purpose of this study is to exetend the concept of sliding friction for various types of nano/micro flows. Design/methodology/approach: A new type of Smoluchowski temperature jump considering the viscous heat generation (sliding friction) has recently been proposed (Le and Vu, 2016b) as an alternative jump condition for the prediction of the surface gas temperature at solid interfaces for high-speed non-equilibrium gas flows. This paper investigated the proposed jump condition for the nano/microflows which has not been done earlier using four cases: 90° bend microchannel pressure-driven flow, nanochannel backward facing step with a pressure-driven flow, nanoscale flat plate and NACA 0012 micro-airfoil. The results are compared with the available direct simulation Monte Carlo results. Also, this paper has demonstrated low-speed preconditioned density-based algorithm for the rarefied gas flows. The algorithm captured even very low Mach numbers of 2.12 × 10−5. Findings: Based on this study, this paper concludes that the effect of inclusion of sliding friction in improving the thermodynamic prediction is case-dependent. It is shown that its performance depends not only on the slip velocity at the surface but also on the mean free path of the gas molecule and the shear stress at the surface. A pressure jump condition was used along with the new temperature jump condition and it has been found to often improve the prediction of surface flow properties significantly. Originality/value: This paper extends the concept of using sliding friction at the wall for micro/nano flows. The pressure jump condition was used which has been generally ignored by researchers and has been found to often improve the prediction of surface flow properties. Different flow properties have been studied at the wall apart from only temperature and heat flux, which was not done earlier. [ABSTRACT FROM AUTHOR]

We propose novel high-order immersed boundary methods for simulating inviscid flows on hierarchical Cartesian grids using the flux reconstruction (FR) method. A high-order distribution of physical quantities derived from the FR method is utilized to interpolate flow variables to maintain the same order near the wall as the interior domain. In particular, the wall's curvature effect is investigated in depth. We validate the accuracy through basic 2-D and 3-D simulations of inviscid flows. Consequently, the same accuracy as the order of the FR method (up to the fourth order) is achieved, including in the near-wall region. • Novel high-order immersed boundary methods for simulating inviscid flows. • Usage of hierarchical Cartesian grids and flux reconstruction method. • Consideration of the wall's curvature effect. • Achievement of the same accuracy as the order of the FR method including in the near-wall region. [ABSTRACT FROM AUTHOR]

This work presents a hybrid method combining the low order boundary element method and the vortex particle method, in the sense that inviscid wake panels are shed from the trailing edge and then converted to vortex particles for viscous simulation of the slipstream flow. The way to combine these two solution techniques are described in detail as well as the methodology to convert wake panels to vortex particles. Two elliptical hydrofoils in the steady flow and an oscillating rectangular hydrofoil are investigated with the hybrid method. It is demonstrated that, to obtain a physical vorticity distribution, the inter-particle spacing cannot be chose arbitrarily, but should be correlated to the boundary layer thickness. The hybrid method shows a good capability to conserve the axial vorticity. The obtained tangential velocity profile across the tip vortex also exhibits an acceptable correlation with experimental measurement. Also presented are the obtained hydrodynamic forces, their convergence with regards to panel size and time step, and the comparison with results of RANS solver and boundary element method. [ABSTRACT FROM AUTHOR]

A numerical model for simulating electro-vortical flows in OpenFOAM is developed. Electric potential and current are solved in coupled solid-liquid conductors by a parent-child mesh technique. The magnetic field is computed using a combination of Biot–Savart’s law and induction equation. Further, a PCG solver with special regularisation for the electric potential is derived and implemented. Finally, a performance analysis is presented and the solver is validated against several test cases. [ABSTRACT FROM AUTHOR]

We present an advection velocity correction (AVC) scheme for interface tracking using the level-set method in this paper. The key idea is to apply a correction to the interface advection velocity at points adjacent to the zero level-set, so as to enforce the preservation of the signed distance function property at these points. As such, the AVC scheme eliminates the need for explicit sub-cell fix approaches as reinitialization at points adjacent to the zero level-set is not needed. This approach of correcting the advection velocity field near the interface and computing the signed distance function; SDF to a high order of accuracy near the interface, rather than applying an explicit sub-cell fix during the reinitialization step represents the key novel aspect of the AVC scheme. We present results from using the AVC scheme along with advection and reinitialization schemes using upwind finite differencing on uniform meshes in this paper. These results are determined for four canonical test problems: slotted disk rotation, deforming sphere, interacting circles and vortex in a box. We compare these results with corresponding results determined using a recently proposed explicit sub-cell fix based reinitialization scheme (CR2). These comparisons show that the AVC scheme yields significantly improved conservation of enclosed volume/area within the interface. Note, the present AVC scheme achieves this by only modifying velocity field values at mesh points. Therefore, the AVC algorithm can in principle be used within the framework of nearly any numerical scheme used to compute interface evolution using the level-set method, even on non-uniform and unstructured meshes, in order to achieve improvements in solution quality. [ABSTRACT FROM AUTHOR]

In this paper we describe a high-resolution transport formulation of the regional level-set approach for an improved prediction of the evolution of complex interface networks. The novelty of this method is twofold: (i) construction of local level sets and reconstruction of a global level set, (ii) local transport of the interface network by employing high-order spatial discretization schemes for improved representation of complex topologies. Various numerical test cases of multi-region flow problems, including triple-point advection, single vortex flow, mean curvature flow, normal driven flow, dry foam dynamics and shock–bubble interaction show that the method is accurate and suitable for a wide range of complex interface-network evolutions. Its overall computational cost is comparable to the Semi-Lagrangian regional level-set method while the prediction accuracy is significantly improved. The approach thus offers a viable alternative to previous interface-network level-set method. [ABSTRACT FROM AUTHOR]

In this paper, the control of 2DOF VIV (two-degree-of-freedom vortex-induced vibration) by Lorentz force has been investigated numerically based on the derivation of stream function-vorticity equations together with the initial and boundary conditions in exponential-polar coordinates attached on a moving cylinder, hydrodynamics forces and the cylinder motion equation. From the derivations of force components, the lift/drag induced by the inertial force only depend on the motion along the corresponding direction, while the lift/drag induced by flow field is affected by the cylinder motion along the two directions. Based on the calculation results, the displacement variation of 2DOF VIV along the transverse direction is similar with that of 1DOF VIV (one-degree-of-freedom vortex-induced vibration). However, the secondary vortex is strengthened with the effect of the pressure side and weakened with the effect of the suction side. With the application of symmetrical Lorentz force, the effects of the pressure/suction side and vortex shedding are weakened, which lead to the suppression of 2DOF VIV. Moreover, the cylinder vibration is fully suppressed and the drag is negative due to the net thrust generated if Lorentz force is large enough, which means the final position of cylinder is at the upstream of the initial position. Furthermore, the fluid-structure interactions from the quiescent cylinder to the steady vibration and then vibration control by Lorentz force are investigated. The shear layers and secondary vortexes grow with the increase of cylinder amplitude and decay with the decrease of cylinder amplitude due to the suppression of cylinder vibration controlled by Lorentz force in the whole process. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to propose a partitioned approach by coupling the smoothed profile method (SPM) and the Euler tension beam model in simulating a vortex-induced vibration of both rigid and flexible cylinders at various reduced velocities.Design/methodology/approach For the fluid part, SPM in the framework of the spectral element method is adopted to simulate the flow. The advantage of SPM lies in modelling multiple complex shapes as it uses a fixed computational mesh without conformation to the geometry of the particles. For the structure part, an elastic-mounted rigid cylinder is considered in two-dimensional (2D) simulations, while a flexible cylinder with a Euler tension beam model is used in three-dimensional simulations.Findings Firstly, in the flow past a freely vibrating cylinder, the maximum vibration responses of the cylinder are about 0.73D and 0.1D in the y and x directions, respectively, which occur at the point Ur = 5.75 and are much higher than Ur = 5 in 2D simulations. It is found that the numerical results from the SPM solver are very consistent with those from the NEKTAR-Arbitrary Lagrangian Eulerian method (NEKTAR-ALE) solver or the NEKTAR-Fourier solver. Furthermore, the flow past the tandem cylinders is also investigated, where the upstream cylinder is static while the downstream one is free to vibrate. Specifically, the beating behaviour is captured from the vibration response of the freely vibrating cylinder under the reduced velocity of Ur = 6 with a gap distance of L = 3.5D.Originality/value The originality of the paper lies in coupling the SEM with the Euler beam model in simulating the vortex induced vibration (VIV) of flexible cylinders. [ABSTRACT FROM AUTHOR]

The energy extraction of two flapping foils with tandem configurations has been studied based on velocity potential theory. The interactions of the hind foil and the vortices of the fore foil with typical oscillatory motions are investigated. The global phase shift, which combines the longitudinal distance and the phase shift of the motions of the two foils, is introduced as the indicating parameter of the interaction modes. The effects of longitudinal distance and phase shift of the motions on the energy extraction efficiency have been analysed. The most favourable global phase shift and the corresponding vortex pattern have been investigated. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to improve the performance of sensorless vector control of induction motor drives by developing a new sliding mode observer for rotor speed and fluxes estimation from measured stator currents and voltages and estimated stator currents.Design/methodology/approach In the present paper, the discontinuity in the sliding mode observer is smoothed inside a thin boundary layer using fuzzy logic techniques instead of sign function to reduce efficiently the chattering phenomenon that affects the rotor speed.Findings The feasibility of the proposed fuzzy sliding mode observer has been verified by experimentation. The experimental results are obtained with a 1 kW induction motor using a dSPACE system with DS1104 controller board showing clearly the effectiveness of the proposed approach in terms of dynamic performance compared to the classical sliding mode observer.Practical implications The experimental results of the whole control structure highlights that this kind of sensorless induction motor drive can be used for variable speed drive in industrial applications such as oil drilling, electric vehicles, high speed trains (HSTs) and conveyers. Such drives may work properly at zero and low speed in both directions of rotation.Originality/value Both the proposed speed observer and the classical sliding mode observer have been developed and implemented experimentally with other adaptive observers for detailed comparison under different operating conditions, such as parameter variation, no-load/load disturbances and speed variations in different speed operation regions. [ABSTRACT FROM AUTHOR]

Numerical modeling of cavitating bubbly flows is challenging due to the wide range of characteristic lengths of the physics at play: from micrometers (e.g., bubble nuclei radius) to meters (e.g., propeller diameter or sheet cavity length). To address this, we present here a multiscale approach which integrates a Discrete Singularities Model (DSM) for dispersed microbubbles and a two-phase Navier Stokes solver for the bubbly medium, which includes a level set approach to describe large cavities or gaseous pockets. Inter-scale schemes are used to smoothly bridge the two transitioning subgrid DSM bubbles into larger discretized cavities. This approach is demonstrated on several problems including cavitation inception and vapor core formation in a vortex flow, sheet-to-cloud cavitation over a hydrofoil, cavitation behind a blunt body, and cavitation on a propeller. These examples highlight the capabilities of the developed multiscale model in simulating various form of cavitation. [ABSTRACT FROM AUTHOR]

In this note, the importance of spectral properties of viscous flux discretization in solving compressible Navier–Stokes equations for turbulent flow simulations is discussed. We studied six different methods, divided into two different classes, with poor and better representation of spectral properties at high wavenumbers. Both theoretical and numerical results have revealed that the method with better properties at high wavenumbers, denoted as α -damping type discretization, produced superior solutions compared to the other class of methods. The proposed compact α -damping method converged towards the direct numerical simulation (DNS) solution at lower grid resolution compared with the other class of methods and is, therefore, a better candidate for high fidelity large-eddy simulations (LES) and DNS studies. • Importance of spectral properties of viscous discretization. • α -damping methods gave physically consistent results. • Non α -damping schemes found unsuitable for marginally resolved simulations. • Viscous flux discretization plays a prominent role in turbulent flow simulations. [ABSTRACT FROM AUTHOR]

A vortex method with penalization is proposed in order to simulate three-dimensional incompressible bluff body flows. This approach combines the robustness of vortex methods and the flexibility of penalization methods to impose boundary conditions on the obstacle. Far field boundary conditions are handled in a FFT-based Poisson solver. A validation of the proposed numerical method is carried out in the context of flow past a sphere and further simulations are performed in the more challenging case of flow past a hemisphere. [ABSTRACT FROM AUTHOR]

We construct an efficient finite volume scheme to solve the three-dimensional vorticity–velocity form of the equations governing incompressible flows. The vorticity transport equations are recast in a form that allows for the development of an accurate upwind scheme. The resulting scheme employs a staggered arrangement of vorticity and velocity and utilizes generalized Riemann problems to determine the numerical flux at the cell faces. The resulting scheme is found to account for convection and stretching of vorticity in a stable manner without the need to perform any additional correction steps to control the divergence of vorticity. Several test cases including isolated and interacting vortices as well as turbulent flow are investigated to assess the effectiveness of the numerical method. [ABSTRACT FROM AUTHOR]

A new method of spatial filtering in high-order finite volume methods is presented and assessed. The base of this method is to filter face-averaged variables (fluxes) and then the recovery of cell-averaged ones. Two kinds of filtering method are proposed. The first kind is highly dissipative and appropriate for the numerical regions that need high dissipation, e.g. sponge zones. The second kind, on the other hand, is a precise method and hence is suitable for applying the high-order finite difference filters to the finite volume methods. Applying high-order finite difference filters directly to the high-order finite volume methods without using the proposed method causes stability problems in the large eddy simulation of high Reynolds number flows. The test cases, namely, propagation of the one-dimensional wave packet, advection of a two-dimensional vortical wave and the large eddy simulation of turbulent round jet at Re = 10 4 and 10 5 are used to examine the accuracy and performance of the proposed methods. The last test case shows the effectiveness of the proposed methods in the large eddy simulation of flows by high-order FVMs. The performance of filtering methods on a curvilinear wavy grid is also investigated. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to present two low diffusive convective-pressure flux split finite volume algorithms for solving incompressible flows in artificial compressibility framework. Design/methodology/approach – The present method follows the framework similar to advection upwind splitting method of Liou and Steffen for compressible flows which is used by Vierendeels et al. to solve incompressible flow equations. Instead of discretizing the total inviscid flux using upwind scheme, the inviscid flux is first split into convective and pressure parts, and then discretized the two parts differently. The convective part is discretized using upwind method and the pressure part using central differencing. Since the Vierendeels type scheme may not be able to capture the divergence free velocity field due to the presence of artificial dissipation term, a strategy to progressively withdraw the dissipation with time step is proposed here that can ascertain the divergence free velocity condition to the level of residual error. This approach helps in reducing the amount of numerical dissipation due to upwind discretization, which is evident from the numerical test examples. Findings – Upwind treatment of only the convective part of the inviscid flux terms, instead of the whole inviscid flux term, leads to more accurate solutions even at relatively coarse grids, which is substantiated by numerical test examples. Research limitations/implications – The method is presently applicable to Cartesian grid. Originality/value – Although similar formulation is reported by Vierendeels et al., no detailed study of the accuracy is presented. Discretization and solution reconstructions used in the present approach differ from the approach reported by Vierendeels et al. A modification to Vierendeels type scheme is proposed that can help in achieving divergence free velocity condition. Finally the efficacy of the present approach to produce very accurate solutions even on coarse grids is successfully demonstrated using a few benchmark problems. [ABSTRACT FROM AUTHOR]

• A high-order solver using flux reconstruction method and lattice Boltzmann flux solver (FR-LBFS) is proposed for nearly incompressible flows. • No particular techniques are required for the pressure-velocity coupling in FR-LBFS. • Inviscid and viscous fluxes are computed uniformly in FR-LBFS. • FR-LBFS is compact for parallel with lower dissipation. In this paper, a novel high-order solver using the flux reconstruction (FR) method and the lattice Boltzmann flux solver (LBFS) is proposed for accurately and efficiently simulating nearly incompressible flows. The existing LBFSs are all based on the finite volume (FV) scheme. The present work extends the application of the LBFS for the first time by combining the high-order FR scheme. Compared with the traditional high-order incompressible Navier-stokes (N-S) solvers, no particular techniques are needed for the current FR-LBFS to overcome the difficulty of the pressure-velocity coupling since the present method is a weakly compressible model. Moreover, unlike the traditional N-S solvers where the inviscid and viscous terms are treated separately, the inviscid and viscous fluxes in the current scheme are coupled and computed uniformly in FR-LBFS. In the present method, the common inviscid and viscous fluxes at the cell interface of the FR scheme are evaluated simultaneously by the local reconstruction of lattice Boltzmann equation (LBE) solution from macroscopic flow variables at solution points. Thus the discretization of the second-order partial derivative term is avoided. Compared with the high-order off-lattice Boltzmann methods (OLBM), the FR-LBFS is more stable, efficient and low-storage. No special techniques are needed to remove the stiffness of the governing equations which existing in the discrete velocity Boltzmann equation (DVBE). Compared with the high-order FV-LBFS, the FR-LBFS is compact for parallel computing by avoiding wide stencils on meshes. In addition, the present scheme has lower dissipation and can be more flexible to increase accuracy order. Numerical validations of the proposed method are implemented by simulating (a) Taylor-Green vortex problem, (b) steady plane Poiseuille flow, (c) lid-driven cavity flow, (d) laminar boundary layer and (e) flow past a square cylinder. [ABSTRACT FROM AUTHOR]

The all-speed Roe schemes still encounter the problem that the original Roe scheme does at high speeds because they are just improved in terms of low speeds. To overcome this problem, we propose a new scheme called RoeMAS (Roe Modified for All Speeds) in this paper. It changes the original Roe scheme’s coefficients D P and D ρU to the order of O(c −1 ) and O(c 0 ) to improve the level of accuracy at low speeds. To be robust against the shock anomaly and the expansion shock at high speeds, it controls the coefficients of the density perturbation in the numerical mass flux instead of controlling those of the pressure perturbation like the RoeM-type schemes. Moreover, it changes the non-linear wave speeds in rarefactions’ simulations to avoid using an entropy fix which is not satisfied in engineering area. Various numerical tests show that RoeMAS satisfies the following attractive properties independent of any tuning coefficient: (1) robustness against the shock anomaly and high discontinuity’s resolution (2) free from the expansion shock’s appearance (3) low dissipation and high resolution at low speeds. These properties suggest that RoeMAS is promising to be widely used to simulate flows of all speeds accurately and efficiently. [ABSTRACT FROM AUTHOR]

Temporally and spatially resolved simulations of turbulent flow need realistic inlet velocity fluctuations. The vortex method, described and implemented in this work, adds vortices to the inlet mean flow profile. The vortices are randomly distributed over the inlet and they move across the extent of the inlet with a finite life-time. The initial vortex sizes, strengths, as well as their developing motion and life-times, are determined by the inlet mean velocity and turbulence distributions. In contrast to previous studies of the vortex method, the inlet mean velocity and turbulence distributions are in the present work theoretically determined, and thus form an explicit part of the boundary condition. This makes the method independent of precursor RANS simulations. Special care has been taken to distribute the vortices evenly across the inlet. The tangential velocity of the vortices is randomly initialized and the spatial and temporal correlation is preserved. An edge bouncing mechanism is implemented at solid boundaries. The boundary condition is applied to a DNS simulation of pipe flow at a Reynolds number of 5300, based on pipe diameter, aiming at reaching fully developed conditions at a short distance from the inlet. The results are compared with those using cyclic boundary conditions, and with two DNS results found in the literature. It is shown that a good agreement is reached for the mean velocity profiles five pipe diameters downstream from the inlet. Also the resolved velocity fluctuations at that location are reasonable. It is concluded that the present implementation of the vortex method boundary condition, based on theoretical mean velocity and turbulence profiles, gives an inlet flow that is sufficiently realistic to reach a well-resolved fully developed turbulent pipe flow at five pipe diameters downstream the inlet. [ABSTRACT FROM AUTHOR]

The article focuses on selecting the right spray nozzles for chemical plants. Topics discussed include reducing the amount of material sprayed, providing a more consistent product, and cutting energy cost; types of nozzles and their applications such as single-fluid nozzle, two-fluid nozzle, and rotary atomizer; and importance of liquid flux distribution (LFD) or patternation.

This study extensively investigates the physics of microscale shock–vortex interaction of argon gas by solving conservation laws with non-Newtonian constitutive relations. In order to solve the conservation laws and associated implicit type second-order constitutive equations of viscous stress and heat flux numerically, a mixed discontinuous Galerkin (DG) formulation is developed. Three major characteristics are found in the microscale shock–vortex interaction in thermal nonequilibrium: the absence of quadrupolar acoustic wave structure, which is the major feature in macroscale near-equilibrium; the increase in the dissipation rate during the strong interaction; and the decrease in enstrophy during the weak interaction. Moreover, we show that the strong shock–vortex interaction in high shock or vortex Mach numbers can cause an increase in enstrophy. We also find the viscous effect to be dominant in the net vorticity generation. Among shock and vortex parameters, the shock Mach number, vortex Mach number and vortex size turn out to play a critical role in the deformation of the vortex and the strength of interaction, which in turn govern the evolution of vorticity due to the viscous effects, the change in the dissipation rate and the increase or decrease in enstrophy during the interaction. [ABSTRACT FROM AUTHOR]

With the rapid development of the Computational Fluid Dynamics (CFD), schemes with higher levels of accuracy, robustness, and efficiency are in increasing demands. To achieve this goal, we propose a new scheme called E-AUSMPW in this paper. This scheme adopts the Zha–Bilgen splitting procedure by theoretical analysis and computes the convection flux like AUSMPW+. Moreover, it uses different methods to simulate the pressure flux’s terms respectively. Series of numerical experiments show that E-AUSMPW is with a high level of robustness against shock anomalies. In addition, it is much more robust against the ‘overheating phenomenon’ than others. Besides these merits above, it is also with high accuracy and high efficiency orders in hypersonic heating predictions. Thus, E-AUSMPW is promising to be widely used to accurately and efficiently simulate both simple and complex flows. [ABSTRACT FROM AUTHOR]

We study the 2+1 dimensional Abelian Higgs model defined on a spatial torus at critical self-coupling. We propose a method to compute the quantum contribution to the mass of the Abrikosov-Nielsen-Olesen vortex and to multivortex energies. The one-loop quantum correction to multivortex energies is computed analytically at the critical value of the torus area (Bradlow limit). For other values of the area one can set up an expansion around this critical area (Bradlow parameter expansion). The method is explained and the next-to-leading term explicitly evaluated. To this order, the resulting energies depend on the torus periods, but not on the vortex positions. [ABSTRACT FROM AUTHOR]

We consider a point particle in one dimension initially confined to a finite spatial region whose state is frequently monitored by projection operators onto that region. In the limit of infinitely frequent monitoring, the state never escapes from the region--this is the Zeno effect. In the corresponding classical problem, by contrast, the state diffuses out of the region with the frequent monitoring simply removing probability. The aim of this paper is to show how the Zeno effect disappears in the classical limit in this and similar examples. We give a general argument showing that the Zeno effect is suppressed in the presence of a decoherence mechanism which suppresses interference between histories. We show how this works explicitly in two examples involving projections onto a one-dimensional subspace and identify the key time scales for the process. We extend this understanding to our main problem of interest, the case of a particle in a spatial region, by coupling it to a decohering environment. Smoothed projectors are required to give the problem proper definition and this implies the existence of a momentum cutoff and minimum length scale. We show that the escape rate from the region approaches the classically expected result, and hence the Zeno effect is suppressed, as long as the environmentally induced fluctuations in momentum are sufficiently large. We establish the time scale on which an arbitrary initial state develops sufficiently large fluctuations to satisfy this condition. We link our results to earlier work on the ħ → 0 limit of the Zeno effect. We illustrate our results by plotting the probability flux lines for the density matrix (which are equivalent to Bohm trajectories in the pure-state case). These illustrate both the Zeno and anti-Zeno effects very clearly, and their suppression. Our results are closely related to our earlier paper [Phys. Rev. A 88, 022128 (2013)], demonstrating the suppression of quantum-mechanical reflection by decoherence. [ABSTRACT FROM AUTHOR]

We present an investigation of generation, dynamics, and stability of dark solitons in anisotropic Fermi gases for a range of particle numbers and trap aspect ratios within the framework of the order-parameter equation. We calculate the periods of dark solitons oscillating in a trap and find good agreement with the results based on the Bogoliubov-de Gennes equations. By studying the stability of initially off-center dark solitons under various tight transverse confinements in the unitarity limit, we not only give the criterion of dynamical stability, but also find that the soliton and a hybrid of solitons and vortex rings can be characterized by different oscillation periods. The stability criterion is not fulfilled by the parameters of the recent experiment of Yefsah et al. [Nature (London) 499. 426 (2013)]. Therefore, instead of a very slow oscillation as observed experimentally, we find that the created dark soliton undergoes a transverse snake instability with a collapse into vortex rings, which propagate in solitonlike manner with a nearly 2 times larger period. [ABSTRACT FROM AUTHOR]

Hypersonic boundary layer on porous surfaces is numerically investigated using the open-source flow solver OpenFOAM. Computations of hypersonic boundary layer have not been widely conducted especially using open-source flow solvers. The solver rhoEnergyFoam Modesti and Pirozzoli (2017), which has been developed in the OpenFOAM framework, is successfully validated for hypersonic boundary layer flow in the current study. Direct numerical simulations (DNS) of boundary layer at Mach 6 are pursued here with a disturbance related to the Mack second mode. The evolution of the Mack second mode is compared with the current analysis of linear stability theory (LST) and previous DNS data. The stabilization of the Mack second mode on porous surfaces is well resolved in the current computations. In addition to the stabilization of the Mack second mode with porous surfaces, aerothermodynamic features, including drag and surface heat transfer, are investigated. Without porous surfaces, the heat flux variation is even larger than the mean heat flux due to the flow instability. Porous surfaces significantly reduce the heat flux variation to the level of the mean heat flux. Mean drag and heat transfer are marginally affected by porous surfaces. Stress analysis is accompanied to investigate whether the pore structure experiences severe stress under such a high-speed condition. The current investigation on porous surfaces indicates that the surface porosity is an effective method to suppress instabilities and subsequently the heat flux variation on the wall without hampering mean aerothermodynamic characteristics. • Direct numerical simulation of the hypersonic boundary layer with the Mack second mode. • Validation of an open-source flow solver in resolving a hypersonic boundary layer. • Detailed analysis on the stabilization of the Mack second mode with porous surfaces. • Investigation on the variation of aerothermodynamic characteristics due to porous surfaces. [ABSTRACT FROM AUTHOR]

Highlights: [•] The dynamics of stall vortex is critical to the disturbance-driven aerodynamics. [•] Stall bubble evolution corresponds to the resonance frequency of about 0.3. [•] Criteria based on stall slope and interval are proposed as the regime boundaries. [•] System’s nonlinearity is assessed by using piecewise linear models. [ABSTRACT FROM AUTHOR]

Highlights: [•] We mitigate the impact of oscillating free-stream on a low-Reynolds number airfoil. [•] Six disturbance regimes are defined based on vortex dynamics. [•] Feedback control performance and mechanisms depend on the disturbance regime. [•] Lift is stabilized by modifying separation bubble evolution and wall pressure. [ABSTRACT FROM AUTHOR]

The article evaluates several industry equipment including the tank floor scanner FloormapVS2i by Silverwing UK Ltd., the tube inspection instrument Ectane by Eddyfi, and the flux leakage tester Rotoflux by Magnetic Analysis Corp.

Composite characteristics of the parallel and serial connections of memristors are investigated. The memristor is one of the fundamental electrical elements, which has recently been successfully built. However, its electrical characteristics are not yet fully understood. When multiple memristors are connected to each other, the composite behavior of the devices becomes complicated and is difficult to predict, due to the polarity dependent nonlinear variation in the memristance of individual memristors. In this work, we investigate the relationships among flux, charge, and memristance of diverse composite memristors, using both linear and nonlinear memristor models, and analyze the characteristics of complex memristor circuits. [ABSTRACT FROM PUBLISHER]

• A cellular automata model for mixed flow systems, composed of higher and lower velocity vehicles with lane changes, is established. • The peak flux of the mixed flow system (vehicles with a distribution of maximal velocity) is lower than that of the default system (constant maximal velocity). • The density that results in the peak flux in mixed flow systems is higher than that of the default system. • In both flow systems, games of the class "defection-dominant prisoner's dilemma" appear close to the density that corresponds to maximal flux. • In the lower density regime, games of the class "defection-dominant trivial" are observed. A new cellular automata traffic model based on Revised S-NFS model is established to consider a mixed flow system in which the maximal velocity of the agents is distributed, as is the case in a real traffic flow fields composed of compact vehicles, trucks, and buses. These vehicles are assigned on of two different strategies: cooperator (C), who remains in his original lane, and defector (D), who undertakes lane-changing to maximize his own payoff, i.e., average velocity. In a systematic series of multi-agent simulations, we quantitatively compare flow characteristics in the default system (where maximal velocity is constant across all agents), mixed traffic flow systems (which permit a distribution of maximal velocities), and correlated–mixed traffic flows, in which an agent with a higher maximal velocity tends to have a D strategy whereas one with a lower maximal velocity tends to have a C strategy. We discuss what kind of game class is underlying in each traffic flow system. Furthermore, we quantitatively study the social efficiency deficit, an index of dilemma extent, for each of the flow systems. [ABSTRACT FROM AUTHOR]

In this work we present ZEFR, a GPU accelerated flow solver based around the high-order accurate flux reconstruction (FR) approach. Written in a combination of C++ and CUDA, ZEFR is designed to perform scale resolving simulations within the vicinity of complex geometrical configurations. A unique feature of ZEFR is its support for overset grids; a feature which greatly expands the addressable problem space compared with existing high-order codes. The C++ implementation of FR in a manner which is suitable for modern hardware platforms is described in detail. Additionally, an overview of the input deck used by ZEFR is included. Validation results are presented for a range of steady and unsteady flow problems including Couette flow, the Taylor–Green vortex, and flow around an SD7003 airfoil. Single node performance on a NVIDIA V100 GPU is analyzed where it is shown that all of the kernels in ZEFR attain a high proportion of peak memory bandwidth. Moreover, multi-node performance is also assessed with strong scalability being demonstrated from 60 to 3840 NVIDIA V100 GPUs. Program title: ZEFR v1.0 Program files doi: http://dx.doi.org/10.17632/wzy83bscxd.1 Licensing provisions: BSD 3-clause Programming language: C++ and CUDA External routines/libraries: Eigen, HDF5, METIS, MPI, and TIOGA. Nature of problem: Compressible Euler and Navier–Stokes equations. Solution method: High-order direct flux reconstruction approach suitable for curved, mixed, unstructured grids. Unusual features: Code incorporates support for overset grids. [ABSTRACT FROM AUTHOR]

The article evaluates the Rosemount 8600 Utility Vortex Flow Meter from Emerson Automation Solutions.

Clustering of like-sign vortices in a planar bounded domain is known to occur at negative temperature, a phenomenon that Onsager demonstrated to be a consequence of bounded phase space. In a confined superfluid, quantized vortices can support such an ordered phase, provided they evolve as an almost isolated subsystem containing sufficient energy. A detailed theoretical understanding of the statistical mechanics of such states thus requires a microcanonical approach. Here we develop an analytical theory of the vortex clustering transition in a neutral system of quantum vortices confined to a two-dimensional disk geometry, within the microcanonical ensemble. The choice of ensemble is essential for identifying the correct thermodynamic limit of the system, enabling a rigorous description of clustering in the language of critical phenomena. As the system energy increases above a critical value, the system develops global order via the emergence of a macroscopic dipole structure from the homogeneous phase of vortices, spontaneously breaking the Z2 symmetry associated with invariance under vortex circulation exchange, and the rotational SO(2) symmetry due to the disk geometry. The dipole structure emerges characterized by the continuous growth of the macroscopic dipole moment which serves as a global order parameter, resembling a continuous phase transition. The critical temperature of the transition, and the critical exponent associated with the dipole moment, are obtained exactly within mean-field theory. The clustering transition is shown to be distinct from the final state reached at high energy, known as supercondensation. The dipole moment develops via two macroscopic vortex clusters and the cluster locations are found analytically, both near the clustering transition and in the supercondensation limit. The microcanonical theory shows excellent agreement with Monte Carlo simulations, and signatures of the transition are apparent even for a modest system of 100 vortices, accessible in current Bose-Einstein condensate experiments. [ABSTRACT FROM AUTHOR]