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Understanding solute transport in pipe flows is essential for ensuring consistent water quality throughout the entire drinking water supply network. This study used four planar laser-induced fluorescence (PLIF) units for the first time to quantify the cross-sectional concentration distribution resulting from a single pulse of tracer injected at an upstream location under both steady and accelerating flow conditions. Compared with conventional fluorometers, PLIF provides a better measure of the cross-sectional mean concentrations because it allows the cross-sectional distribution of the tracer to be quantified. Under steady turbulent flow conditions, the tracer was cross-sectionally well-mixed, and the concentration uniformity increased with increasing Reynolds number. In laminar flows, as a result of minimal radial mixing, the tracer exhibited a spatial distribution created by the longitudinal differential advection, transforming from a central core to an annulus, which expanded toward the pipe boundary. Under accelerating flows, the temporal concentration profiles displayed two peaks and the tracer close to the source was not cross-sectionally well-mixed. With increasing discharge, the tracer became cross-sectionally well-mixed while retaining the two peak profiles. These results have implications for water quality modeling in unsteady conditions, especially in domestic plumbing, when boundary and biofilm interactions control important processes. [ABSTRACT FROM AUTHOR]

In this paper, a comparative study on MHD forced convective flow for heat transfer efficiency of different nanofluids with water (H2O) as base fluid has been carried out. Here, in this study flow through vertical rectangular has been considered in presence of strong magnetic field. In this laminar flow we consider duct walls as electrically non-conducting where the transverse magnetic field acting normally on the duct walls. Joule heat and the viscous dissipation effects are included in the energy equation and furthermore the walls of the duct are kept at constant temperature. An explicit finite difference method has been adopted with fine grid in the control volume for solving the governing equations of this MHD nanofluid flow. Computational processes are carried out using MATLAB code. In this present work we have plotted the flow fields velocity, induced magnetic field, and temperature for various values of MHD flow parameters graphically by varing thermal Grashof number (Gr), Hartmann number (Ha), Reynold number (Re), Eckert number (Ec), Prandtl number (Pr), magnetic Reynold number (Rm), and nanoparticle volume fraction (ϕ) respectively.

In this paper, a comparative study on MHD forced convective flow for heat transfer efficiency of different nanofluids with water (H2O) as base fluid has been carried out. Here, in this study flow through vertical rectangular has been considered in presence of strong magnetic field. In this laminar flow we consider duct walls as electrically non-conducting where the transverse magnetic field acting normally on the duct walls. Joule heat and the viscous dissipation effects are included in the energy equation and furthermore the walls of the duct are kept at constant temperature. An explicit finite difference method has been adopted with fine grid in the control volume for solving the governing equations of this MHD nanofluid flow. Computational processes are carried out using MATLAB code. In this present work we have plotted the flow fields velocity, induced magnetic field, and temperature for various values of MHD flow parameters graphically by varing thermal Grashof number (Re), Hartmann number (Ec), Reynold number (Pr), Eckert number (Rm), Prandtl number (Pr), magnetic Reynold number (Rm), and nanoparticle volume fraction (φ) respectively. [ABSTRACT FROM AUTHOR]

The analysis and microcontroller implementation of a Newtonian fluid-filled porous medium heated from the bottom and subjected to sinusoidal or non-sinusoidal periodic gravity is investigated in this paper. The Newtonian fluid-filled porous medium with a bottom source of heat and subjected to periodic gravity modulation is described by the equation of conservation of energy and hydrodynamic equations modified following the Boussinesq–Darcy approximation. Galerkin-truncated approximation is applied in reducing the resulting set of partial differential equations into a Lorenz-like system of ordinary differential equations of order 1. The Lorenz-like system obtained in this case is found to have three equilibrium points whose stability depends on the system parameters. Without gravity modulation and by varying the scaled Rayleigh number, it is demonstrated that the obtained Lorenz-like system displays steady convection, periodic convection, chaotic convection, reverse period doubling to chaotic convection and coexistence between steady and chaotic convections. In the presence of sinusoidal or non-sinusoidal periodic gravity modulation and by varying the scaled Rayleigh number, the obtained Lorenz-like system exhibits periodic convections, bistable periodic convections and period doubling to chaotic convections. Finally, the existence of periodic convections, bistable periodic convections and chaotic convections is confirmed by microcontroller results obtained from the microcontroller implementation of the obtained Lorenz-like system. [ABSTRACT FROM AUTHOR]

The effect of rotation rate parameter, cylinder diameter, and the variation of Reynolds number on the circular cylinder was the main object of this 2D numerical study. Rotating and stationary circular cylinder in steady and unsteady incompressible flow has been analysed. For each value of Reynolds number, we have varied the rotation rate parameter clockwise and anti-clockwise to visualize their effect on the drag, lift, and coefficients. All cases have carried out steady laminar, unsteady laminar, and turbulent regimes. A realizable K-epsilon model has been used to solve the Navier Stokes equations for the turbulent regime. Results were in good agreement with the recent findings.

Discussed in this investigation is the three-dimensional gravity-driven flow of a thin fluid layer down an incline and over topography. A new three-dimensional integral-boundary-layer (IBL) model is proposed to describe the flow. Numerical simulations are presented and comparisons with lubrication and two-dimensional IBL models are discussed for both steady and unsteady flows. Subcritical and supercritical cases are considered, along with symmetrical and asymmetrical bottom topographies. Also, good agreement was found with experiments. [ABSTRACT FROM AUTHOR]

In this paper, we survey the volume growth estimates for shrinking, steady, and expanding gradient Ricci solitons. Together with the known results, we also prove some new volume growth estimates for expanding gradient Ricci solitons. [ABSTRACT FROM AUTHOR]

The main purpose of the current article is to scrutinize the flow of hybrid nanoliquid (ferrous oxide water and carbon nanotubes) (CNTs + Fe 3 O 4 /H 2 O) in two parallel plates under variable magnetic fields with wall suction/injection. The flow is assumed to be laminar and steady. Under a changeable magnetic field, the flow of a hybrid nanofluid containing nanoparticles Fe 3 O 4 and carbon nanotubes are investigated for mass and heat transmission enhancements. The governing equations of the proposed hybrid nanoliquid model are formulated through highly nonlinear partial differential equations (PDEs) including momentum equation, energy equation, and the magnetic field equation. The proposed model was further reduced to nonlinear ordinary differential equations (ODEs) through similarity transformation. A rigorous numerical scheme in MATLAB known as the parametric continuation method (PCM) has been used for the solution of the reduced form of the proposed method. The numerical outcomes obtained from the solution of the model such as velocity profile, temperature profile, and variable magnetic field are displayed quantitatively by various graphs and tables. In addition, the impact of various emerging parameters of the hybrid nanofluid flow is analyzed regarding flow properties such as variable magnetic field, velocity profile, temperature profile, and nanomaterials volume fraction. The influence of skin friction and Nusselt number are also observed for the flow properties. These types of hybrid nanofluids (CNTs + Fe 3 O 4 /H 2 O) are frequently used in various medical applications. For the validity of the numerical scheme, the proposed model has been solved by another numerical scheme (BVP4C) in MATLAB. [ABSTRACT FROM AUTHOR]

A channel confined flow around a bluff object is significantly different from its unconfined counterpart. A confined flow is presumably more stabilized due to the presence of the confinement. This causes a delay in the onset of flow separation and vortex shedding in comparison to the unconfined flow. While the above facts have been reported for the confined flow around a circular object in a channel, the same for a square object is infrequent. The present study focuses on the steady flow past a stationary square cylinder placed in a channel at low Reynolds numbers 1 ≤ Re ≤ 30 . The behavior of the flow is observed through numerical simulation for various channel confinements ( 0.01 ≤ B ≤ 0.9 , blockage ratio). The steady state laminar two-dimensional incompressible flow equations are solved using a finite volume based technique. An effort is made to find the separation critical Reynolds number at all blockages. It is observed that the separation critical Reynolds number increases with an increase in the blockage ratio. Unsteady flow characteristics at various blockages are also studied at Re = 100. In the unsteady regime, the frequency of vortex shedding increases with an increase in the blockage. [ABSTRACT FROM AUTHOR]

This paper investigates a polygonal finite element (PFE) to solve a two-dimensional (2D) incompressible steady fluid problem in a cavity square. It is a well-known standard benchmark (i.e., lid-driven cavity flow)-to evaluate the numerical methods in solving fluid problems controlled by the Navier– Stokes (N–S) equation system. The approximation solutions provided in this research are based on our developed equal-order mixed PFE, called Pe1Pe1. It is an exciting development based on constructing the mixed scheme method of two equal-order discretisation spaces for both fluid pressure and velocity fields of flows and our proposed stabilisation technique. In this research, to handle the nonlinear problem of N-S, the Picard iteration scheme is applied. Our proposed method’s performance and convergence are validated by several simulations coded by commercial software, i.e., MATLAB. For this research, the benchmark is executed with various Reynolds numbers up to the maximum Re = 1000. All results then numerously compared to available sources in the literature. [ABSTRACT FROM AUTHOR]

Abstract Relative permeability (k r) and the capillary pressure (P c) are the central key elements defining the multiphase fluids flow behavior in the porous media. However, the dynamic capillarity should consider the dynamic relative permeability and the dynamic capillary pressure while performing waterflooding process in extremely low permeable formations. In order to improve the oil production, the advanced horizontal well drilling along with multiple hydraulic fracturing is generally instigated to penetrate the unconventional resources. The aim of this study is to consider the dynamic capillarity in a commercial reservoir simulation, while utilizing the data gained from the dynamic and steady experiments of the relative permeability and the capillary pressure impacts during waterflooding process in the core plugs of unconventional tight oil reservoirs. The commercial reservoir simulation conducted sensitivity analyses using Computer Modeling Group simulator. The outcomes show that the well production of the reservoir is overestimated while implementing steady data for forecasting due to which the oil saturation decreases more equally and further rapidly. Additionally, the forecast of the well production estimated to breakthrough sooner. However, neglecting the dynamic capillarity causes a huge breakthrough of water influx. Therefore, the core objective of this study is to probe the consequences of taking into consideration the dynamic capillarity in ultra-low permeable formations while giving an alternative perspective to forecast the production of the hydraulically fractured unconventional tight oil reservoirs.

This paper studies the uniqueness of steady 1-D shock solutions in a finite flat nozzle via vanishing viscosity arguments. It is proved that, for both barotropic gases and non-isentropic gases, the steady viscous shock solutions converge under the L1 norm. Hence only one shock solution of the inviscid Euler system could be the limit as the viscosity coefficient goes to 0, which shows the uniqueness of the steady 1-D shock solution in a finite flat nozzle. Moreover, the position of the shock front for the limit shock solution is also obtained. [ABSTRACT FROM AUTHOR]

In this paper we study the nature of Ricci solitons in D-homo-thetically deformed Kenmotsu manifolds. We prove that η -Einstein Kenmotsu metric as a Ricci soliton remains η -Einstein under D-homothetic deformation and the scalar curvature remains constant.

The main purpose of the current article is to scrutinize the flow of hybrid nanoliquid (ferrous oxide water and carbon nanotubes) (CNTs + Fe3O4/H2O) in two parallel plates under variable magnetic fields with wall suction/injection. The flow is assumed to be laminar and steady. Under a changeable magnetic field, the flow of a hybrid nanofluid containing nanoparticles Fe3O4 and carbon nanotubes are investigated for mass and heat transmission enhancements. The governing equations of the proposed hybrid nanoliquid model are formulated through highly nonlinear partial differential equations (PDEs) including momentum equation, energy equation, and the magnetic field equation. The proposed model was further reduced to nonlinear ordinary differential equations (ODEs) through similarity transformation. A rigorous numerical scheme in MATLAB known as the parametric continuation method (PCM) has been used for the solution of the reduced form of the proposed method. The numerical outcomes obtained from the solution of the model such as velocity profile, temperature profile, and variable magnetic field are displayed quantitatively by various graphs and tables. In addition, the impact of various emerging parameters of the hybrid nanofluid flow is analyzed regarding flow properties such as variable magnetic field, velocity profile, temperature profile, and nanomaterials volume fraction. The influence of skin friction and Nusselt number are also observed for the flow properties. These types of hybrid nanofluids (CNTs + Fe3O4/H2O) are frequently used in various medical applications. For the validity of the numerical scheme, the proposed model has been solved by another numerical scheme (BVP4C) in MATLAB.

Relative permeability (kr) and the capillary pressure (Pc) are the central key elements defining the multiphase fluids flow behavior in the porous media. However, the dynamic capillarity should consider the dynamic relative permeability and the dynamic capillary pressure while performing waterflooding process in extremely low permeable formations. In order to improve the oil production, the advanced horizontal well drilling along with multiple hydraulic fracturing is generally instigated to penetrate the unconventional resources. The aim of this study is to consider the dynamic capillarity in a commercial reservoir simulation, while utilizing the data gained from the dynamic and steady experiments of the relative permeability and the capillary pressure impacts during waterflooding process in the core plugs of unconventional tight oil reservoirs. The commercial reservoir simulation conducted sensitivity analyses using Computer Modeling Group simulator. The outcomes show that the well production of the reservoir is overestimated while implementing steady data for forecasting due to which the oil saturation decreases more equally and further rapidly. Additionally, the forecast of the well production estimated to breakthrough sooner. However, neglecting the dynamic capillarity causes a huge breakthrough of water influx. Therefore, the core objective of this study is to probe the consequences of taking into consideration the dynamic capillarity in ultra-low permeable formations while giving an alternative perspective to forecast the production of the hydraulically fractured unconventional tight oil reservoirs. [ABSTRACT FROM AUTHOR]

A packed-bed thermal energy storage (PBTES) device, which is simultaneously restricted by thermal storage capacity and outlet temperatures of both cold and hot heat transfer fluids, is characterized by an unstable operation condition, and its calculation is complicated. To solve this problem, a steady thermodynamics model of PBTES with fixed temperatures on both ends was built. By using this model, the exergy destruction, thermocline thickness, thermal storage capacity, thermal storage time, and other key parameters can be calculated in a simple way. In addition, the model explained the internal reason for the change of thermocline thickness during thermal storage and release processes. Furthermore, the stable operation of the PBTES device was analyzed, and it was found that higher inlet temperature of hot air, and lower temperature difference between cold and hot air can produce less exergy destruction and achieve a larger cycle number of stable operation. The work can be employed as the basis of the design and engineering application of PBTES. [ABSTRACT FROM AUTHOR]

• First, in the framework of the Dirichlet-Robin interface condition, it is shown that the normalized distance between the stability bound and the optimal coefficient is equal to the inverse of the numerical Biot number. • Then, we demonstrate that this optimal coefficient is directly connected to two fundamental thermal quantities: the penetration depth and the thermal effusivity. • A thorough examination of the amplification factor (and its derivative) of the coupled thermal problem highlights a small-varying zone. This establishes a reasonable range of values for the coupling coefficient for high thermal fluid-structure interactions. • An example shows that such a coefficient is able to stabilize high thermal fluid-structure interactions (unstable with the optimal coefficient) but also the reasonable value of this coefficient avoids significantly impairing the accuracy of a CHT solution. The goal of this paper is to propose a single interface treatment, based on the Dirichlet-Robin interface condition to deal with all steady CHT scenarios. These scenarios depend on the so-called numerical Biot number that controls the stability process and the optimal coefficient that ensures, in theory, unconditional stability. It is shown that this coefficient is closely related to fundamental thermal quantities. For very large thermal fluid-solid interactions, the Dirichlet-Robin condition may result in profound stability issues. A thorough examination of the stability behavior has highlighted a narrow and slow-varying stable zone located around the optimal coefficient. This allows us to determine coupling coefficients valid in any case and the reasonable value of these coefficients avoids significantly impairing the accuracy of CHT solutions. A flat plate, partially protected by a thermal barrier coating, is presented as a test case. [ABSTRACT FROM AUTHOR]

Shear stress of physiological flows in the human body plays a critical role in maintaining the structure and functions of single cells and multicellular organs. Recently, the wide-spreading microfluidic technologies have made significant contributions to the in-vitro recapitulation of complex biochemical and mechanical cues. Microfluidic approaches are of inherent advantages in modeling of flow shear stress (FSS) because they can i) precisely modulate the type, magnitude and exposure time of FSS, ii) control the biochemical microenvironment for cell culture, and iii) be integrated with advanced microscopy techniques to enable real-time and high-resolution imaging of cell response to FSS. Here we review the microfluidic FSS models developed in the past years. We firstly introduce the various physiological flows existing in human bodies, then discuss how microfluidics modeled FSS in vitro, and finally elaborate on applications of these models in cell biology, disease modeling and drug development. • The basics and significance of various physiological flows in the human body were overviewed. • Microfluidic approaches mimicking physiological/pathological flow shear stress were discussed. • Applications of the microfluidic shear stress models in cell biology, disease modeling and drug development were discussed in detail. [ABSTRACT FROM AUTHOR]

This paper presents an optimization of a high pressure turbine by constructing non-axisymmetric endwalls to the stator row and the rotor hub. The optimization was quantified by using optimization algorithms based on the multi-objective function. The objective was to increase total-to-total efficiency with the constraint on the mass flow rate equal to the design point value. In order to ensure that global optimum could be achieved, the function of parameters was first approximated through the artificial neural network, and then optimum was achieved by implementing the genetic algorithm. It was adopted through the design and optimization environment of Fine™/Design3D. Three individual treatments of the endwalls were presented. Firstly, the hub and the shroud of the stator were optimized together. Secondly, the hub of the rotor was optimized. Thirdly, the rotor hub was optimized in the presence of the optimized stator. The result of the investigation showed that the optimized shape of the endwalls can significantly help to increase the efficiency up to 0.18% with the help of a reduction of the transverse pressure gradient. The coefficient of secondary kinetic energy, entropy coefficient, spanwise mass averaged entropy were reduced. In order to investigate the periodic effects, the design of the optimized turbine under steady simulations was confirmed through unsteady simulations. The last part of the investigation made sure that the performance improvement remained consistent over the full operating line at off-design conditions by the implementation of non-axisymmetric endwalls. [ABSTRACT FROM AUTHOR]

Bernoulli's equation is a certain case of a fluid flow problem. Some restrictions must be met in order to correctly apply this particular equation. The fluid flow must be considered inviscid, incompressible, steady and irrotational. However, if the fluid flow is rotational, Bernoulli's equation can still be applicable as long as the points of interest are on the same streamline of the fluid flow. Here, we will focus on demonstrate that, in the case of a rotational fluid flow, the points of interest must be on the same streamline and because of that, it can be proceeding with the usage of Bernoulli's equation. The principle is only applicable for isentropic fluid flows: when the effects of irreversible processes (e.g. turbulence, friction) and non-adiabatic processes (e.g. heat radiation, mass diffusion) are small and can be neglected. [ABSTRACT FROM AUTHOR]

The objective of the current paper is to study the flow around Seiun Maru Highly Skewed (HSP) marine propeller by assessment of blade forces and moments under non-cavitating case. The calculations are performed in open water (steady case) and non-uniform ship wake (Unsteady case). The governing equations based on Reynolds Averaged Navier-Stokes Equation (RANSE) are solved using Finite Volume Method. Ansys Fluent 14.0 is used to implement the simulation. For the steady case, Moving Reference Frame (MRF) is selected while sliding mesh technique is adopted for the unsteady case. Calculated open water performances in terms of thrust and torque coefficients fit very well with experimental data for a wide range of advance ratio. In the unsteady calculations, axial velocities, deduced from the nominal wake, are introduced in the Ansys fluent code. To locate suitably the non-uniform wake in the propeller front plane, three positions of inlet wake have been taken into account to determine their effects on the accuracy of the results. Obtained results show that computed performances are improved compared to panel method when the inlet is close to the propeller. [ABSTRACT FROM AUTHOR]

Abstract Global primary energy consumption will continue to increase with a high rate to 2050, which will be a big challenge for countries to meet both global and regional energy demand. Pumped storage stations (PSS) integrated to a hybrid power system (HPS) with solar and wind power for China are under construction to tussle with this challenge. Historically, modeling of a PSS integrated HPS has been ignored the interaction effect between the shaft vibration and the governing strategies, which will increase the dynamic risk of PSS disconnected immediately to HPS. Here we unify the models of the hydro-turbine governing system and hydro-turbine generator units with a novel expression of hydraulic forces. We quantize all the parameter's interaction contributions of PSS integration to HPS and validate this model with the existing models. Finally, we show the feasibility of PSS's model in integrating of a HPS under steady and fault scenarios. [ABSTRACT FROM AUTHOR]

In this paper we study Ricci solitons in generalized D-conformally deformed Kenmotsu manifold and we analyzed the nature of Ricci solitons when associated vector field is orthagonal to Reeb vector field. [ABSTRACT FROM AUTHOR]

Quantitative detection of HSA in biological fluids is essential for pre-clinical diagnosis. Herein a TICT based HSA sensor NJUP1 was introduced for detection in healthy and hypertension blood samples. It interacted with domain IIA of HSA to generate a turn-on response. The detection mechanism was convinced by HSA destruction, site competition, molecular docking and isothermal titration calorimetry. NJUP1 suggested advantages such as rapid (response time 5 s), steady (more than 24 h), sensitive (LOD 18.1 nM, up to 200-fold enhancement), selective (∼6 fold over 10 times BSA in mass), wide detection range (covering blood samples requirements) and low toxicity, among which several were top class. Most importantly, it possessed only ∼300 molecular weight and one connecting double bond. It could be applied in urine system and blood samples. Thus, NJUP1 provided a potential approach for further applications. [ABSTRACT FROM AUTHOR]

In this paper the steady lateral growth of three-dimensional turbulent inclined turbidity current is investigated. To simulate the current, an experimental setup is developed to analyze the turbidity current for different regimes in the particle laden density currents environment. The Buckingham’s π theorem together with a dimensional analysis is implemented to derive the appropriate non-dimensional variables. The experimental results were normalized and plotted in the form of non-dimensional graphs from which a theoretical model is developed and analyzed. Based on the results obtained for the steady lateral growth, three different regimes, namely, inertia-viscous one as the first regime, buoyancy-viscous and gravity-viscous as the second and third regimes are distinguished within the current. In these regimes, the force balance is between the driving and resisting forces. Namely, in the first regime, the force balance is between the inertia and viscous forces, in the second regime, the buoyancy and viscous forces, and in the third regime, gravity and viscous forces are balanced. The experimental results indicate that the lateral growth rate in the first regime is smaller than that in the second and third regimes due to the magnitude and type of the forces involved in those regimes. According to the graphical results, the three different lateral growth rates appear when the normalized current length is smaller than about 3, between about 3 and 10, and larger than about 10. In those regions, the slopes of the data are different with respect to one another. [ABSTRACT FROM AUTHOR]

Energy efficiency retrofit of buildings represents a key effort in reducing EU energy demand by 20% by 2020. However, predictions tend to overestimate savings by large percentages. The shortfall in savings can be attributed to incorrect predictive techniques, comfort takeback along with other behavioural and workmanship variables. Common predictive techniques related to heat loss tend to be based on the U-value of the building envelope. This paper presents the design of a more straightforward and compact version of the traditional Hot-Box apparatus (measures U-value) which instead determines the thermal resistance of samples of building envelope. U-value includes the need to measure/predict the effective surface resistances. In situ surface resistances, which include radiation and convection, are difficult to predict and vary depending on climatic conditions, exposure levels, surface emissivities among many other influences. The design of the test facility eliminates the need to incorporate these surface behaviour variables. This paper details the replicable apparatus and test methodology. The results of testing a hollow block wall of typical construction using the rig is then presented. The determined R-value is found to be within 1% of calculated values and the thermal time constant also matches closely with the most accurate predictive estimates. [ABSTRACT FROM AUTHOR]

Coupling analysis plays more and more important roles in recent years for the accurately modelling of nuclear reactors. But with the different discretization methods adopted in different physical phenomena, it is difficult to couple different kinds of codes. In this paper, steady and transient-state neutronics solvers have been developed based on the finite volume method which is widely used for the simulation of fluid flow and heat and mass transfer. With the adoption of this discretization method, mesh mapping technique and data exchange become much easier for the coupling codes compared with traditional methods. The developed neutronics solvers are verified by several benchmark problems. Numerical results indicate that the developed neutronics solvers are reliable to be applied for the steady-state and transient-state neutronics analysis of nuclear reactors. [ABSTRACT FROM AUTHOR]

Coupling analysis plays more and more important roles in recent years for the accurately modelling of nuclear reactors. But with the different discretization methods adopted in different physical phenomena, it is difficult to couple different kinds of codes. In this paper, steady and transient-state neutronics solvers have been developed based on the finite volume method which is widely used for the simulation of fluid flow and heat and mass transfer. With the adoption of this discretization method, mesh mapping technique and data exchange become much easier for the coupling codes compared with traditional methods. The developed neutronics solvers are verified by several benchmark problems. Numerical results indicate that the developed neutronics solvers are reliable to be applied for the steady-state and transient-state neutronics analysis of nuclear reactors. [ABSTRACT FROM AUTHOR]

In this paper, RANS CFD simulations of steady and unsteady upwind sail aerodynamics are verified and validated against wind tunnel experiments previously performed at Politecnico di Milano. Experimental data is presented, and the experimental results are analysed to estimate repeatability. Blockage effects caused by tunnel boundary layers and measurement equipment are estimated using detailed CFD simulations, allowing such effects to be accounted for. A verification procedure is performed, resulting in very low numerical uncertainties. The force predictions are then validated for both steady and unsteady conditions. The steady results show very good agreement, with a maximum error of 3.1%. For the unsteady conditions, good agreement is found for the force mean values, whilst the prediction of force amplitudes is less satisfactory. [ABSTRACT FROM AUTHOR]

We are concerned with the stability of multidimensional (M-D) transonic shocks in steady supersonic flow past multidimensional wedges. One of our motivations is that the global stability issue for the M-D case is much more sensitive than that for the 2-D case, which requires more careful rigorous mathematical analysis. In this paper, we develop a nonlinear approach and employ it to establish the stability of weak shock solutions containing a transonic shock-front for potential flow with respect to the M-D perturbation of the wedge boundary in appropriate function spaces. To achieve this, we first formulate the stability problem as a free boundary problem for nonlinear elliptic equations. Then we introduce the partial hodograph transformation to reduce the free boundary problem into a fixed boundary value problem near a background solution with fully nonlinear boundary conditions for second-order nonlinear elliptic equations in an unbounded domain. To solve this reduced problem, we linearize the nonlinear problem on the background shock solution and then, after solving this linearized elliptic problem, develop a nonlinear iteration scheme that is proved to be contractive. [ABSTRACT FROM AUTHOR]

We are concerned with the two-dimensional steady supersonic reacting Euler flow past Lipschitz bending walls that are small perturbations of a convex one, and establish the existence of global entropy solutions when the total variation of both the initial data and the slope of the boundary is sufficiently small. The flow is governed by an ideal polytropic gas and undergoes a one-step exothermic chemical reaction under the reaction rate function that is Lipschtiz and has a positive lower bound. The heat released by the reaction may cause the total variation of the solution to increase along the flow direction. We employ the modified wavefront tracking scheme to construct approximate solutions and develop a Glimm-type functional by incorporating the approximate strong rarefaction waves and Lipschitz bending walls to obtain the uniform bound on the total variation of the approximate solutions. Then we employ this bound to prove the convergence of the approximate solutions to a global entropy solution that contains a strong rarefaction wave generated by the Lipschitz bending wall. In addition, the asymptotic behavior of the entropy solution in the flow direction is also analyzed. [ABSTRACT FROM AUTHOR]

Effect of radiation and mass transfer on the transient free convection flow of a dissipative past semi-infinite vertical plate with uniform heat and mass flux is analyzed, by taking into account the effect of viscous dissipation. This type of problems finds application in many technological and engineering fields such as plasma studies, petroleum industries, MHD energy generators, cooling of nuclear reactors, the boundary layer control in aerodynamics, crystal growth and furnace engineering. The Rosseland approximation is used to describe the radiative heat transfer in the limit of the optically thick fluid. The non-linear, coupled equations are solved using an implicit finite difference scheme of Crank-Nicolson type. Transient temperature, concentration and velocity profiles, local and average skinfriction coefficient, Nusselt number and Sherwood number are presented graphically and discussed. It is observed that, when the radiation parameter increases the velocity and temperature decrease accompanied by simultaneous reduction in both momentum and thermal boundary layers.

Aim of the paper is to investigate the effects of linearly varying viscosity and thermal conductivity on steady free convective flow of a viscous incompressible fluid along an isothermal vertical plate in the presence of heat sink. The governing equations of continuity, momentum and energy are transformed into coupled and nonlinear ordinary differential equations using similarity transformation and then solved using Runge-Kutta fourth order method with shooting technique. The velocity and temperature distributions are discussed numerically and presented through graphs. Skin-friction coefficient and Nusselt number at the plate are derived, discussed numerically and their numerical values for various values of physical parameters are presented through Tables.

Aim of the paper is to investigate effects of variable thermal conductivity and heat source/sink on flow of a viscous incompressible electrically conducting fluid in the presence of uniform transverse magnetic field and variable free stream near a stagnation point on a non-conducting stretching sheet. The equations of continuity, momentum and energy are transformed into ordinary differential equations and solved numerically using shooting method. The velocity and temperature distributions are discussed numerically and presented through graphs. Skin-friction coefficient and the Nusselt number at the sheet are derived, discussed numerically and their numerical values for various values of physical parameter are presented through Tables.

In the present investigation compressibility effect on two-dimensional steady natural convection boundary layer flow of a viscous fluid past a vertical plate has been studied. The governing equations are transformed into a non-dimensional form and the solutions are obtained by four different methods, namely, a perturbation method for the small values of local compressibility variable, ξ , asymptotic solutions for large ξ , the direct finite difference method and the implicit finite difference method with Keller-box scheme for all ξ . In order to examine the results obtained from the four methods, calculations have been carried out for a wide range of parameters. The results obtained by the above mentioned four methods are compared and found in excellent agreement. Moreover, the effects of various practical values of the relative temperature difference, α , and the surface temperature wave amplitude a on the local skin friction, the rate of heat transfer and the isotherms are shown graphically. [ABSTRACT FROM AUTHOR]

Queen's University Belfast and Wave Barrier Ltd have developed a tidal testing platform to test hydrokinetic turbines at medium scale. Multiple turbines can be pushed through still water conditions, in steady-state pushing tests. Experiments were conducted to evaluate the interactions between two identical, mono-strut, horizontal axis tidal turbines (HATTs) of 1.5 m diameter ( D ) rotor. Their relative performance when located individually, in-plane and in-line are investigated. The data shows a high consistency in the power curves at different flow speeds, which indicates high repeatability in this Reynolds range. For an individual turbine, there is no performance difference when the rotor is mounted either upstream or downstream of the supporting structure. When placed in-plane, the turbines have no adverse effect on one another. When spaced in-line with 2 D separation, there is a 63% reduction in the performance of the downstream turbine. At 6 D downstream this performance reduction is still 59%, indicating some wake recovery between 2D and 6D , though the influence from the upstream rotor persists to at least 6 D downstream of the first device. In contrast the performance of the downstream turbine when placed at 1.5 D offset of the upstream device at 6 D downstream is approximately recovered to the individual turbine performance. [ABSTRACT FROM AUTHOR]

In this paper we give a characterisation of Ricci solitons in Ricci recurrent and ϕ-recurrent Kenmotsu manifolds based on the 1-form. [ABSTRACT FROM AUTHOR]

This paper puts forward use of a Kalman filter algorithm to improve the accuracy and the stability of a four rotor aircraft control. The algorithm principle used covariance to estimate the system's optimal output. The flight and control theory of a four rotor aircraft was first analyzed; furthermore, it was found that the attitude angle had the biggest influence on its control. Then the Kalman filter model was established for processing attitude angle information from gyro and accelerometer sensors. Finally, the algorithm was compared with a complementary filter. The flight conditions were simulated in different flight environments; it is shown that the Kalman filter algorithm can improve the precision and real time in attitude angle acquisition. [ABSTRACT FROM AUTHOR]

The present work investigated numerically the onset of the transition from steady to unsteady laminar flow regime in a three dimensional complex geometry. The behavior of the dynamic and thermal fields of the chaotic fluid flow has been analyzed for numerous Reynolds numbers ranging from 190 to 550. Several parameters were used during this study to verify the fluid pattern such as; velocity and temperature profiles, secondary flow, flow intensity, helicity and the Nusselt number. It is found that at Re = 400, the symmetry of the flow is destroyed in the second and the third geometric periods whereas it still remains present in the first period which indicates the first step towards the transition. While at Re = 445, the symmetry is still preserved in the first period of the geometry, but the velocity begins to be unsteady with periodic variation at a single frequency where a clear impression can be given on the transition from the steady laminar regime to the unsteady regime. Results illustrate that the flow goes through intermediate steps to reach the unsteady domain before exiting the laminar zone. Moreover, the flow in the geometry of interest is not of the same nature so it can be totally or partially unsteady where different stages can be cited as; stable and symmetric flow, stable asymmetric flow, unstable flow with one or more frequencies and finally erratic flow. [ABSTRACT FROM AUTHOR]