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Squeeze film dampers are used to reduce vibration in aircraft jet engines supported by rolling element bearings. The underlying physics of the squeeze film dampers has been studied extensively over the past 50 years. However, the research on the SFDs is still ongoing due to the complexity of modeling of several effects such as fluid inertia and the modeling of the piston rings, which are often used to seal SFDs. In this work, a special experimental setup has been designed to validate the numerical models of SFDs. This experimental setup can be used with various SFD geometries (including piston ring seals) and simulate almost all conditions that may occur in an aircraft jet engine. This work also focuses on the inertia forces of the fluid. The hydrodynamic pressure distribution of a detailed 3D-CFD model is compared with the solution of the Reynolds equation including inertia effects. Finally, the simulation results are compared with experimental data and good agreement is observed. [ABSTRACT FROM AUTHOR]

In this study, an extended Reynolds equation incorporating the shape errors and the inertia effects of compressible fluid was formulated. The pressure-solving equation for the gas film was constructed using a second-order finite difference method. By combining the measurement data from the cylindricity of multiple shafts obtained from a cylindricity measuring instrument, the variation of the aerostatic bearing load capacity with the rotation of the shaft was calculated, both with and without considering the inertia effect. An experimental rig was also constructed to measure the error motion data of the corresponding shaft. The results of numerical analysis and experimental validation demonstrated that shafts with larger cylindricity error values exhibit greater deviations in the calculated bearing load capacity, which correspondingly leads to larger radial error motion values measured in the experiment. When the roundness error value of the shaft is small or the shaft speed is low, the influence of inertial effects on the calculation results of the load capacity deviation is minimal and can generally be disregarded. [ABSTRACT FROM AUTHOR]

Squeeze film dampers are used to reduce vibration in aircraft jet engines supported by rolling element bearings. The underlying physics of the squeeze film dampers has been studied extensively over the past 50 years. However, the research on the SFDs is still ongoing due to the complexity of modeling of several effects such as fluid inertia and the modeling of the piston rings, which are often used to seal SFDs. In this work, a special experimental setup has been designed to validate the numerical models of SFDs. This experimental setup can be used with various SFD geometries (including piston ring seals) and simulate almost all conditions that may occur in an aircraft jet engine. This work also focuses on the inertia forces of the fluid. The hydrodynamic pressure distribution of a detailed 3D-CFD model is compared with the solution of the Reynolds equation including inertia effects. Finally, the simulation results are compared with experimental data and good agreement is observed.

As a diffusionless phase transformation, martensite evolves at the speed close to sound, with its kinetics and morphology dominated by the mechanical energy. However, the mechanism of martensitic phase transformation with the consideration of inertia is rarely investigated. This paper presents a multiphase-field model, where the transformation strain in martensite performs as the mechanical wave source, and in return the kinetic energy contributes to the driving force for phase transformation. As a result, the mechanical fields, i.e., the stress and the velocity, are derived according to the increment of the transformation strain. The propagation direction of the mechanical wave is corrected by considering the growth of the martensitic nucleus. With the 1D and 2D analysis, as well as the comparison against 2D static case, the mechanism of martensitic phase transformation is investigated, and the advantage of mechanical model accounting for inertia effects is illustrated. [Display omitted] • A multiphase-field model including dynamic mechanics is proposed. • The transformation strain in martensite acts as a mechanical wave source. • The kinetic energy contributes to the driving force. • The mechanism of martensitic phase transformation is investigated in 1D and 2D cases. • The multiphase-field model with dynamic mechanics is more accurate than static. [ABSTRACT FROM AUTHOR]

Studies on the impact of changes in travel costs on car and public transport use are typically based on cross-sectional travel survey data or time series analysis and do not capture intrapersonal variation in travel patterns, which can result in biased cost elasticities. This paper examines the influence of panel effects and inertia in travel behaviour on travel cost sensitiveness, based on four waves of the Mobility Panel for the Netherlands (comprising around 90,000 trips). This paper analyses the monetary costs of travel. Panel effects reflect (within wave) intrapersonal variations in mode choice, based on three-day trip diary data available for each wave. The impact of intrapersonal variation on cost sensitiveness is shown by comparing mode choice models with panel effects (mixed logit mode choice models with error components) and without panel effects (multinomial logit models). Inertia represents variability in mode choice between waves, measured as the effect of mode choice decisions made in a previous wave on the decisions made in the current wave. Additionally, all mode choice models include socio-economic and spatial variables but also mode preferences and life events. The effect of inertia on travel cost elasticities is measured by estimating mixed logit mode choice models with and without inertia effects. The main conclusion is that the inclusion of intrapersonal effects tends to increase cost sensitiveness whereas the inclusion of inertia effects decreases travel cost sensitiveness for car and public transport modes. Car users are identified as inert travellers, whereas public transport users show a lower tendency to maintain their usual mode choice. This paper reveals the inertia effects over four waves of repeated respondent's data repeated yearly. [ABSTRACT FROM AUTHOR]

Fluid production from fractured rock masses readily induces fracture flow velocities of meters per second. Yet, most discrete fracture flow models treat flow as laminar creeping flow or account for inertia effects only by single-fracture constitutive relationships. This numeric simulation study investigates water flow patterns and spatial velocity variations in a natural fracture network with mm-wide open fractures, studying the transition from laminar creeping to turbulent flow. After verification with a fracture intersection model, a Reynolds-time-averaged Navier Stokes solver serves to analyse flow regimes and velocity distribution. Our results show that for fracture flow velocities greater than ∼ 1-cm/s, fluid inertia begins to markedly alter flow patterns and the overall velocity distribution in the network. The pressure-gradient-flow relationship therefore becomes non-linear long before the flow in straight fractures enters the weak inertia regime. This prominence of inertia effects highlights the need to improve fracture network flow models. [Display omitted] • First fracture-trace-map-scale flow simulations considering inertia effects. • Single-fracture-based approximations are inapplicable to fracture networks. • Marked deviations from laminar creeping flow occur at cm/s flow velocities. • Bernoulli effect leads to flow reversal in some subordinate fractures. • Different flow regimes coexist in the fracture network at elevated flow rates. [ABSTRACT FROM AUTHOR]

In this paper, a multilobe conical bearing is analyzed. A lubricant modelled by a couple stress fluid flows in the bearing clearance. The Galerkin method is used to determine the mechanical parameters of multilobe journal bearings. An example of a two-lobe conical bearing is discussed in detail. The inertia of the flowing lubricant is taken into account in the analysis. It has been found that the increase of the couple stress generates an increase the pressure in the clearance.

In view of the increasing attention to the time responses of complex fluids described by power-laws in association with the need to capture inertia effects that manifest in high-frequency microrheology, we compute the five basic time-response functions of in-series or in-parallel connections of two elementary fractional derivative elements known as the Scott-Blair (springpot) element. The order of fractional differentiation in each Scott-Blair element is allowed to exceed unity reaching values up to 2 and at this limit-case the Scott-Blair element becomes an inerter—a mechanical analogue of the electric capacitor that its output force is proportional only to the relative acceleration of its end-nodes. With this generalization, inertia effects may be captured beyond the traditional viscoelastic behavior. In addition to the relaxation moduli and the creep compliances, we compute closed-form expressions of the memory functions, impulse fluidities (impulse response functions) and impulse strain-rate response functions of the generalized fractional derivative Maxwell fluid, the generalized fractional derivative Kelvin-Voigt element and their special cases that have been implemented in the literature. Central to these calculations is the fractional derivative of the Dirac delta function which makes possible the extraction of singularities embedded in the fractional derivatives of the two-parameter Mittag-Leffler function that emerges invariably in the time-response functions of fractional derivative rheological models. [ABSTRACT FROM AUTHOR]

In this paper, we study the flow through a corrugated channel filled with a fluid-saturated sparsely packed porous medium. The porous medium flow is described by the Darcy–Lapwood–Brinkman system taking into account the Brinkman extension of the Darcy law and the flow inertia. We assume the periodicity of the roughness in the longitudinal direction and that the flow is governed by the prescribed pressure drop between the edges of the channel. Introducing average boundary roughness as the small parameter, we propose a higher-order correction of the Darcy–Brinkman filtration velocity via asymptotic analysis. [ABSTRACT FROM AUTHOR]

Extreme industrial conditions require a bearing which can withstand high-speed operations, heavy load, high stiffness and so on. Therefore in this study, the combined effects of fluid inertia forces and non-Newtonian characteristic with Herschel-Bulkley fluid as lubricant in an externally pressurized converging thrust bearing have been contemplated. Avoiding complex calculation, the term inertia in the momentum equation is estimated by the mean value average method across the film thickness. A mathematical model for converged thrust bearing has been introduced. Using appropriate boundary conditions, thickness of the core, velocity profile, film pressure and the load carrying capacity of the bearing for various values of Herschel-Bulkley number (N), Reynolds number (Re), Power-law index (n) and angle of convergence (ip) have been numerically computed. Having worked with an externally pressurized flow through a narrow clearance between two convergent disks symmetrical with respect to r and z axis, it is found that the converged bearing performance such as pressure distribution and load carrying capacity increases notably. The results obtained in this study is found to be in agreement with the results of Jayakaran et al. (2012), for a particular case. [ABSTRACT FROM AUTHOR]

In order to simulate the characteristics of acoustic levitation for freely floating states with a larger ratio between the excitation radius and film thickness, a group of governing equations including a modified Reynolds, movement, and vibration equations were derived in this article. The inertia effect was considered in the modified Reynolds equation (MRE) and compared to experimental vibration curves. The vibration curves were interpolated from the experimental data on disc modal shapes with the standing wave's excitation. The effect of wave numbers and amplitudes on floating height and bearing capacity are discussed in this article. The results indicate that the amplitudes of the excitation disc are approximately linear with the floating height, and the larger wave number along R direction can induce not only better bearing capacity but also floating stability. It is concluded that there would be more accurate results for floating height calculated by the MRE considering inertia effects. This squeeze film model with the MRE can aid in the design of actuators. [ABSTRACT FROM AUTHOR]

The wave-induced motions, and steady wave forces and moments for the oil tanker KVLCC2 in regular head and oblique waves are numerically predicted by using the expanded RANS solver based on OpenFOAM. New modules of wave boundary condition are programed into OpenFOAM for this purpose. In the present consideration, the steady wave forces and moments include not only the contribution of hydrodynamic effects but also the contribution of the inertial effects due to wave-induced ship motions. The computed results show that the contribution of the inertial effects due to heave and pitch in head waves is non-negligible when wave-induced motions are of large amplitude, for example, in long waves. The influence of wave amplitude on added resistance in head waves is also analyzed. The dimensionless added resistance becomes smaller with the increasing wave amplitude, indicating that added resistance is not proportional to the square of wave amplitude. However, wave amplitude seems not to affect the heave and pitch RAOs significantly. The steady wave surge force, sway force and yaw moment for the KVLCC2 with zero speed in oblique waves are computed as well. The present RANS results are compared with available experimental data, and very good agreements are found between them.

The flow of a couple-stress lubricant in a clearance of a curvilinear thrust hydrostatic bearing with impermeable walls is considered. The flow in the bearing clearance is considered with inertia forces. The equations of motion are solved by an averaged inertia method. As a result, the formulae for pressure distributions without and with inertia effects were obtained. Radial thrust bearings and spherical bearings are discussed as numerical examples. It is shown that inertia effects influence the bearing performance considerably.

Many electrorheological fluids (ERFs) as fluids with micro-structure demonstrate a non-Newtonian behaviour. Rheometric measurements indicate that some flows of these fluids may by modelled as the flows of a Vočadlo ER fluid. In this paper, the flow of a Vočadlo fluid – with a fractional index of non-linearity – in a narrow gap between two fixed surfaces of revolution with a common axis of symmetry is considered. The flow is externally pressurized and it is considered with inertia effect. In order to solve this problem the boundary layer equations are used. The Reynolds number effects (the effects of inertia forces) on the pressure distribution are examined by using the method of averaged inertia terms of the momentum equation. Numerical examples of externally pressurized flows in the gap between parallel disks and concentric spherical surfaces are presented.

This work represents closed-form analytical expressions for the operating parameters for short-length open-ended squeeze film dampers, including the lubricant velocity profiles, hydrodynamic pressure distribution, and lubricant reaction forces. The proposed closed-form expressions provide an accelerated calculation of the squeeze film damper parameters, specifically for rotordynamics applications. In order to determine the analytical solutions for the squeeze film damper parameters, the thin film equations for lubricant are introduced in the presence of the influence of lubricant inertia. Subsequently, two different analytical techniques, namely the momentum approximation method, and the perturbation method are applied to the thin film equations. Moreover, the solution for the lubricant flow equations are analytically determined to represent closed-form expressions for the hydrodynamic pressure distribution and the velocity component profiles in squeeze film dampers. Additionally, the expressions for the hydrodynamic pressure distribution are integrated over the journal surface, either numerically or analytically by using Booker's integrals, to develop expressions for the fluid film reaction forces. Lastly, the developed squeeze film damper models are incorporated into simulation models in Matlab and Simulink®, and the results are compared against a well-established force coefficient model to verify the accuracy of the calculations. The results of the simulations verify the effect of the lubricant inertia components, namely the convective and temporal (i.e., unsteady) inertia components on the squeeze film damper dynamics, including hydrodynamic pressure distribution and fluid film reaction forces. Additionally, the simulation results suggest a close agreement between the proposed models and the results in the literature. [ABSTRACT FROM AUTHOR]

In normal functioning conditions, the primary component of the flow within the rod bundle of a PWR core is in the axial direction, along the rods. However, in accidental situations, such as the refilling or reflooding phase during a Loss of Coolant Accident, or a Steam Line Break accident, transverse flows may significantly affect thermal-hydraulic properties in the core. Such effects have received little attention in system codes such as CATHARE, particularly in anisotropic rod structures at low Reynolds numbers. Here, we develop macroscopic pressure drop models for flows spanning from the creeping regime to unsteady vortex shedding. The averaged model is a generalized Darcy–Forchheimer equation with an apparent permeability including a rotation matrix and a non-linear dimensionless coefficient. The constitutive relations for the intrinsic permeability matrix are derived from polynomial regressions based on results obtained from microscale numerical simulations at different flow directions and Reynolds numbers. We finally test our approach in a case where transverse flow is imposed through a differential of inlet velocities and validate by comparing results from CATHARE with those obtained from a finite element toolbox. • Cross-flows in PWR core are investigated. • A pressure drop model using a porous media approach is developed for low Reynolds numbers. • Pressure drop model is based on a generalized Darcy–Forchheimer equation. • Pressure drop model is assessed against a case with asymmetrical velocities at the inlet of two rod-bundles. [ABSTRACT FROM AUTHOR]

Analytical and numerical analyses are carried out in order to reveal the importance of the cellular materials topology for their dynamic compaction. The aim is to distinguish between the deformation and energy absorption mechanisms of materials which exhibit local structural softening, such as out-of-plane loaded honeycomb, and materials with local structural hardening (foam). It is shown that the dynamic out-of-plane compaction of honeycombs does not obey the law of shock wave propagation and a new phenomenological model of the velocity attenuation is proposed. It is revealed that the absorbed energy by the honeycomb is proportional to the area under the dynamic stress-strain curve, which is defined by the foil material properties, in contrast to the shock-wave propagation model where the absorbed energy is proportional to the area under the shock chord. Comparisons with the predictions of the Rigid Perfectly-Plastic Locking (RPPL) model, which approximates well the average quasi-static stress-strain characteristic of a honeycomb, are discussed. Special attention is given to the effects of neglecting the honeycomb topology on their response to impact loading. Finite element simulations are carried out to verify the proposed theoretical model revealing the major factors which influence the dynamic response of out-of-plane loaded honeycombs to high velocity impact. [ABSTRACT FROM AUTHOR]

This work proposes a numerical model that incorporates the effect of lubricant inertia on the hydrodynamic pressure distribution, fluid film reaction forces, and the fluid velocity component profiles for finite-length open-ended squeeze film dampers (SFDs). Firstly, the thin film flow equations for the SFD in presence of fluid inertia effects are introduced. Furthermore, a small first-order perturbation by means of the expressions for the fluid film velocity components and the lubricant pressure distribution that are expanded in power series of the squeeze film Reynolds number is applied to the flow equations. Subsequently the developed lubricant flow equations are solved to develop expressions for the velocity component profiles and the hydrodynamic pressure distribution in SFDs. The pressure expression is numerically solved by using Gauss–Seidel method with finite difference discretization. Moreover, the fluid film reaction forces are determined by numerically integrating the hydrodynamic pressure expressions over the journal surface. Additionally, the proposed pressure distribution expression and the numerical SFD forces are incorporated into a simulation model and the simulation results are compared with the existing models in the literature under different operating conditions, including eccentricity ratios and inertia effects (i.e., Reynolds numbers). The simulation results demonstrate the significant influence of both convective and temporal (i.e., unsteady) lubricant inertia terms on the SFD hydrodynamic pressure distribution and the fluid film reaction forces. Furthermore, the proposed SFD model is incorporated into a multi-mass flexible rotordynamic model to evaluate the effect of SFD fluid inertia on the mass unbalance induced steady-state vibrations of the rotor and the nodal transient orbits by implementing finite element method and transient modal integration with predictor–corrector solver. The results of the analysis demonstrate the significant effect of fluid inertia on the resonance frequencies of the rotor and the steady-state vibration amplitudes and the transient orbits at the resonance zone. [ABSTRACT FROM AUTHOR]

The series hybrid electric vehicle makes it easier to have fully independent controls for the engine–generator unit and for the traction motors; this is not feasible in parallel hybrid electric vehicles or series–parallel hybrid electric vehicles. The existing research does not consider this feature. Therefore, a novel control method called engine torque command handling is developed in this study and is added to the optimal energy management strategy, namely dynamic programming; this makes the most of the inertia of the engine–generator unit. The hidden fuel economy improvement factor, as demonstrated by the the difference between the command and the behaviour, can then be found. As a result, a considerable improvement in the fuel economy with straightforward but powerful concepts, such as modification of the engine operating points and the on–off period, is developed in the series hybrid electric bus. The simulation is evaluated by AMEsim–Simulink co-simulation with the well-known urban bus test profiles: the Manhattan cycle, the Braunschweig cycle and the Orange County cycle. The results show the significant potential for reduction in the energy consumption without changing the components or the structure of the vehicle system. This method can be applied to any type of vehicle that allows independent engine power generation without interruption. [ABSTRACT FROM AUTHOR]

This work proposes a numerical model that incorporates the effect of lubricant inertia on the hydrodynamic pressure distribution, fluid film reaction forces, and the fluid velocity component profiles for finite-length open-ended squeeze film dampers (SFDs). Firstly, the thin film flow equations for the SFD in presence of fluid inertia effects are introduced. Furthermore, a small first-order perturbation by means of the expressions for the fluid film velocity components and the lubricant pressure distribution that are expanded in power series of the squeeze film Reynolds number is applied to the flow equations. Subsequently the developed lubricant flow equations are solved to develop expressions for the velocity component profiles and the hydrodynamic pressure distribution in SFDs. The pressure expression is numerically solved by using Gauss–Seidel method with finite difference discretization. Moreover, the fluid film reaction forces are determined by numerically integrating the hydrodynamic pressure expressions over the journal surface. Additionally, the proposed pressure distribution expression and the numerical SFD forces are incorporated into a simulation model and the simulation results are compared with the existing models in the literature under different operating conditions, including eccentricity ratios and inertia effects (i.e., Reynolds numbers). The simulation results demonstrate the significant influence of both convective and temporal (i.e., unsteady) lubricant inertia terms on the SFD hydrodynamic pressure distribution and the fluid film reaction forces. Furthermore, the proposed SFD model is incorporated into a multi-mass flexible rotordynamic model to evaluate the effect of SFD fluid inertia on the mass unbalance induced steady-state vibrations of the rotor and the nodal transient orbits by implementing finite element method and transient modal integration with predictor–corrector solver. The results of the analysis demonstrate the significant effect of fluid inertia on the resonance frequencies of the rotor and the steady-state vibration amplitudes and the transient orbits at the resonance zone.

The microdevice designed in the present work can sort and separate submicrometer particles in the size range of 0.1–1 µm by introducing the thermophoretic effect. Simulations were conducted in which particles were considered to be a discrete phase and their trajectories were tracked with the Lagrangian approach. The numerical results showed that 0.1-, 0.5-, and 1.0-µm-diameter particles could be separated from each other at positions of 30, 63, and 82 µm above the center of the channel, respectively, when a 10 K temperature difference between the bottom and upper walls was imposed. The focusing positions shift to −30, 36, and 62 μm above the center of the channel when a 2 K temperature difference imposed. These results were in good agreement with those of the force analysis and experiments. The importance of the thermophoretic effect for submicroparticle sorting is therefore demonstrated by the numerical simulations and experiments. [ABSTRACT FROM AUTHOR]

Neglecting of end effects in rotational viscometry introduces 10-30 % error in the estimate of shear stress σ at surface of rotating cylindrical spindle. Actual values of the correction coefficient cfor a real sensor depend on pseudoplasticity level of a given sample (measured by the flow-behavior index n) and inertia level (measured by the Reynolds number Re). The correction coefficients for the real sensors with coaxial cylinders are calculated by solving the related flow problem for Generalized Newtonian Fluid with power-law viscosity function. In addition to the cylindrical sensors according to ISO 3219 CEN Bruxelles 53:019, () , also some clones with different geometry simplex H = h/ R are considered. The results on c( n, Re, H) are presented as a simple empirical formula for easy use in downstream treatment of primary data using the pseudosimilarity approach. [ABSTRACT FROM AUTHOR]

This paper presents an improved understanding of the dynamic focusing process and lateral migration dynamics of microparticles throughout a classic spiral microchannel at finite Reynolds numbers. A novel two-stage model is proposed to elucidate the particle focusing process along the channel. Specifically, we find that particle migration undergoes a two-stage development comprising the formation of the particle array (stage I) and the shifting of the focusing position after particles are well focused (stage II). Variations in particle focusing ratio and lateral focusing position under different migration lengths and different driving flow rates are quantitatively investigated and analyzed. Results show that the cross-sectional Dean flow affects the particle migration dynamics throughout the channel more significantly at large Reynolds numbers. It is also found that an unstable focusing phenomenon occurs at the intermediate channel region in addition to at the outlets. A state diagram is then generated to illustrate the occurrence and development of this interesting focusing instability along the channel. In addition, the focusing performances of a mixture of different size particles are investigated to reveal the multi-particle separation process and mechanism. The small particle is found to contribute more significantly to the variation in the relative positions of multi-particles. These improved understandings of the particle focusing mechanisms provide insights into the device optimization and the operation protocol improvement. [ABSTRACT FROM AUTHOR]

The inertia effects on strategy updating in emergency evacuation from a room with multiple exits is studied using the modified floor field model. Game theory is adopted to deal with conflict resolving process of evacuees and inertia effects are introduced in both exit choosing and conflict resolving process. From simulation results, the influences of inertia effects on the evacuation times and cooperation frequencies have been discussed. Interestingly, it can be found that inertia effects in exit choosing may lead more evacuation times, while inertia effects in conflict resolving may lead more evacuation times and higher cooperation frequencies. This study provides a new perspective to understand how the inertia of changing status quo acts on the strategy evolution in emergency circumstances. [ABSTRACT FROM AUTHOR]

Abstract: The Couette viscometer is a well-known problem of fluid mechanics, well-suited for the verification of numerical methods. The aim of this work is to extend the classical steady state mechanical solution obtained in fluid mechanics, both to strongly-coupled thermomechanical problems in the case of laminar and incompressible fluid flows, and to solid-type nonlinear behaviours. Extended solutions will allow for the verification of new formulations of a mixed P1+/P1 finite element developed both in fluid and solid mechanics, within a temperature/velocity/pressure formulation coupled with an implicit (backward) Euler algorithm in time. In the present Part I, we address the case of the laminar flow of incompressible fluids with inertia effects and thermomechanical coupling. The verification performed on the reference solutions developed clearly evidence the good behaviour of the fluid finite element. The extension to solid-type nonlinear behaviours for strongly-coupled thermomechanical problems will be the subject of Part II. [Copyright &y& Elsevier]

Highlights: [•] The flow of viscoplastic fluids through expansion-contraction is studied. [•] The fluid behavior is given by the GNL model with the SMD viscosity function. [•] Inertial effects are shown to break the fore-aft symmetry of the stagnant unyielded region and to reduce the size of the islet formed by the axis. [ABSTRACT FROM AUTHOR]

We consider computational modeling of flow with small and large velocities at porescale and at corescale, and we address various challenges in simulation, upscaling, and modeling. While our focus is on voxel-based data sets from real porous media imaging, our methodology is verified first on synthetic geometries, and we analyze various scaling and convergence properties. We show that the choice of a voxel-based grid and representative elementary volume size can lead up to 10-20 % difference in calculated conductivities. On the other hand, the conductivities decrease significantly with flow rates, starting in a regime usually associated with the onset of inertia effects. This is accompanied by deteriorating porescale solver performance, and we continue our experiments up until about 50 % reduction in conductivities, i.e., to Reynolds number just under 1. To account for this decrease, we propose a practical power-based fully anisotropic non-Darcy model at corescale for which we calculate the parameters by upscaling. [ABSTRACT FROM AUTHOR]

A novel Kolsky torsion bar technique is developed and successfully utilized to characterize the high strain rate shear response of a rate-independent end-linked polydimethylsiloxane (PDMS) gel rubber with a shear modulus of about10 KPa. The results show that the specimen deforms uniformly under constant strain rate and the measured dynamic shear modulus follows reasonably well the trend determined by dynamic mechanical analysis (DMA) at lower strain rates. For comparison, Kolsky compression bar experiments are also performed on the same gel material with annular disk specimens. The dynamic moduli obtained from compression experiments, however, are an order of magnitude higher than those obtained by the torsional technique, due to the pressure caused by the radial inertia and end constraints. [ABSTRACT FROM AUTHOR]

Abstract: The helium cooled lead lithium (HCLL) blanket concept is one of the designs that will be tested and validated in the experimental reactor ITER. The liquid metal, which is slowly circulated in the blanket, interacts with the magnetic field that confines the fusion plasma leading to modifications of velocity and pressure distributions compared to the ones in hydrodynamic flows. Experiments have been performed to investigate magnetohydrodynamic flows in a scaled mock-up of a HCLL blanket. One of the aims is identifying the geometric elements that give rise to the main contributions to the total pressure head in the module. Parametric studies have been carried out to assess the influence of flow rate and magnetic field intensity on pressure drops. [Copyright &y& Elsevier]

A theoretical investigation of the laminar squeeze flow of a couple-stress fluid between a flat circular static disk and an axisymmetric curved circular moving disk has been carried out using modified lubrication theory and microcontinuum theory. The combined effects of fluid inertia forces, curvature of the disk and non-Newtonian couple stresses on the squeeze film behavior are investigated analytically. Each of these effects and their combinations show a significant enhancement in the squeeze film behavior, and these are studied through their effects on the squeeze film pressure and the load carrying capacity of the fluid film as a function of time. Two different forms of the gapwidth between the disks have been considered, and the results have been shown to be in good agreement with the existing literature. [ABSTRACT FROM AUTHOR]

Abstract: We present an approach based on Gronwall’s inequalities for the asymptotic complete phase–frequency synchronization of Kuramoto oscillators with finite inertia. For given finite inertia and coupling strength, we present admissible classes of initial configurations and natural frequency distributions, which lead to the complete phase–frequency synchronization asymptotically. For this, we explicitly identify invariant regions for the Kuramoto flow, and derive second-order Gronwall’s inequalities for the evolution of phase and frequency diameters. Our detailed time-decay estimates for phase and frequency diameters are independent of the number of oscillators. We also compare our analytical results with numerical simulations. [ABSTRACT FROM AUTHOR]

Classical hydrodynamic lubrication theory has been one of the most successful and widely used theories in all of engineering and applied science. This theory predicts that the force resisting the squeezing of a fluid between two parallel plates is inversely proportional to the cube of the fluid thickness. However, recent reports on liquid squeeze film damping in microsystems appear to indicate that experimentally measured damping force is proportional to the inverse of the fluid thickness to the first power--a large fundamental discrepancy from classical theory. This paper investigates potential limitations of lubrication theory in microsystems by theoretical and computational methods. The governing equations for a Newtonian incompressible fluid are solved subject to two-dimensional, parallel surface squeezing by an open-source computational fluid dynamics program called parallel hierarchic adaptive stabilized transient analysis (PHASTA), and by a classical similarity solution technique. At low convective Reynolds numbers, the damping force is determined as a function of the ratio of a reference film thickness H to a reference direction B along the film. Good agreement with classical lubrication theory is found for aspect ratios H/B as high as 1 despite the fact that lubrication theory requires that this ratio be "small." A similarity analysis shows that when instantaneous convective Reynolds number is of order 10-100 (a range present in experiment), calculated damping deviates significantly from lubrication theory. This suggests that nonlinearity associated with high Reynolds numbers could explain the experimentally observed discrepancy in damping force. Dynamic analysis of beams undergoing small vibrations in the presence of a liquid medium further supports this finding. [ABSTRACT FROM AUTHOR]

Inertia effects are seldom considered in morphological modeling, and most of the transport models were developed from laboratory experiments in steady uniform flow conditions. This paper considers first the hysteresis effects in transient flows between discharge, velocity, and bottom shear stress. These effects can be taken into account as far as the complete shallow-water equations are used. Secondly, inertia effects linked to the sediment response to acting forces are considered. Three types of models are investigated: (i) sediment movement instantaneously adapting to hydrodynamic changes, (ii) spatial or temporal lag laws to give space or time to the sediments to progressively reach the transport capacity, and (iii) a two-layer model, able to account for the inertia of the sediment layer. Finally, three examples are presented: a scour hole downstream of an apron, a jump over a mobile bed, and a dam-break wave. Inertia effects appear significant in the modeling, especially the latter case. [ABSTRACT FROM AUTHOR]

Determination of dynamic tensile response of soft materials has been a challenge because of experimental difficulties. Split Hopkinson tension bar (SHTB) is a commonly used device for the characterization of high-rate tensile behavior of engineering materials. However, when the specimen is soft, it is challenging to design the necessary grips, to measure the weak transmitted signals, and for the specimen to achieve dynamic stress equilibrium. In this work, we modified the SHTB on the loading pulse, the equilibrium-monitoring system, and the specimen geometry. The results obtained using this modified device to characterize a soft rubber indicate that the specimen deforms under dynamic stress equilibrium at a nearly constant strain rate. Axial and radial inertia effects commonly encountered in dynamic characterization of soft materials are also minimized. [ABSTRACT FROM AUTHOR]

Concrete is heterogeneous and usually described as a three-phase material, where matrix, aggregate and interface are distinguished. To take this heterogeneity into consideration, the Generalized Beam (GB) lattice model is adopted. The GB lattice model is much more computationally efficient than the beam lattice model. Numerical procedures of both quasi-static method and dynamic method are developed to simulate fracture processes in uniaxial tensile tests conducted on a concrete panel. Cases of different loading rates are compared with the quasi-static case. It is found that the inertia effect due to load increasing becomes less important and can be ignored with the loading rate decreasing, but the inertia effect due to unstable crack propagation remains considerable no matter how low the loading rate is. Therefore, an unrealistic result will be obtained if a fracture process including unstable cracking is simulated by the quasi-static procedure. [ABSTRACT FROM AUTHOR]

A numerical modeling of thermoelastohydrodynamic mechanical face seal behavior is presented. The model is an axisymmetric one and it is confined to high pressure compressible flow. It takes into account the behavior of a real gas and includes thermal and inertia effects, as well as a choked flow condition. In addition, heat transfer between the fluid film and the seal faces is computed, as are the elastic and thermal distortions of the rings. In the first part of this paper, the influence of the coning angle on mechanical face seal characteristics is studied. In the second part, the influence of the solid distortions is analyzed. It is shown that face distortions strongly modify both the gap geometry and the mechanical face seal's performance. The mechanical distortions lead to a converging gap, while the gas expansion, by cooling the fluid, creates a diverging gap. [ABSTRACT FROM AUTHOR]

Abstract: A numerical method is used to compute the flow field corresponding to blast waves of different incident profiles propagating in air and impinging on free-standing plates. The method is suitable for the consideration of compressibility effects in the fluid and their influence on the plate dynamics. The history of the pressure experienced by the plate is extracted from numerical simulations for arbitrary blast strengths and plate masses and used to infer the impulse per unit area transmitted to the plate. The numerical results complement some recent analytical solutions in the intermediate range of plate masses and arbitrary blast intensities where exact solutions are not available. The resulting beneficial effect of the fluid–structure interaction (FSI) in reducing transmitted impulse in the presence of compressibility effects is discussed. In particular, it is shown that in order to take advantage of the impulse reduction provided by the FSI effect, large plate displacements are required which, in effect, may limit the practical applicability of exploiting FSI effects in the design of blast-mitigating systems. [Copyright &y& Elsevier]