Inertial Mechanisms Research Articles

Twin tubular pinch effect in curving confined flows.

Colloidal suspensions of buoyancy neutral particles flowing in circular pipes focus into narrow distributions near the wall due to lateral migration effects associated with fluid inertia. In curving flows, these distributions are altered by Dean currents and the interplay between Reynolds and Dean numbers is used to predict equilibrium positions. Here, we propose a new description of inertial lateral migration in curving flows that expands current understanding of both focusing dynamics and equilibrium distributions. We find that at low Reynolds numbers, the ratio δ between lateral inertial migration and Dean forces scales simply with the particle radius, coil curvature and pipe radius as . A critical value δc = 0.148 of this parameter is identified along with two related inertial focusing mechanisms. In the regime below δc, coined subcritical, Dean forces generate permanently circulating, twinned annuli, each with intricate equilibrium particle distributions including eyes and trailing arms. At δ > δc (supercritical regime) inertial lateral migration forces are dominant and particles focus to a single stable equilibrium position.

SOLAR CELLS WITH THE CHARGE PUMPING: THEORETICAL PERSPECTIVES AND TECHNOLOGICAL ASPECTS OF THE APPLICATION

The analysis of the inertial mechanisms of separating photoexcited carriers in conventional silicon converters structure with charges pumps (SCSCP) is lead. Charges pumps represented local n +-areas in Si base of p -type of conductivity. The equivalent circuit of such converters like multyemitters bipolar transistor is proposed. The results of experimental investigations converters light current-voltage diagrams are presented. Technological aspects of SCSCP formation is regarded.

A 3D method to evaluate moisture losses in a low pressure steam turbine: Application to a last stage

This paper presents a physically consistent 3D method to evaluate moisture losses and it is further employed to estimate the moisture losses in the last stage of a 1000MW fossil-fired steam turbine. The 3D method is based on the information of the flow-field and droplets deposition. An inhomogeneous multi-phase flow model is adopted to simulate the condensing flow in the last stage. Massive computations of droplets deposition by both inertial and turbulent mechanisms on the stationary blade and moving blade have been conducted for different droplet diameters at the inlet of the last stage. In our work, the moisture losses are divided into six categories namely thermodynamic loss, drag loss of fog droplets, drag loss of coarse droplets, impact loss, capturing loss and centrifuging loss. The effect of the fog droplet size at the inlet of the last stage on the moisture losses has been analyzed and the results indicate that the overall moisture losses rise and the relative fractions of each category of the moisture losses vary against the increase of the fog droplet diameter.

Dynamic process and flow-rate regulation mechanism of particle inertial focusing in an asymmetric ally curved microchannel

In this paper, an asymmetrically curved microchannel device is designed and fabricated to quantitatively characterize the dynamic inertial focusing process of polystyrene particles and blood cells flowing along the channel. The experimental investigations are systematically carried out to probe into the regulation mechanisms of flow rate and particle size. Specifically, based on the particle fluorescent streak images and the corresponding intensity profiles at specific downstream positions, the lateral migration behaviors of particles in the mirochannel can be divided into two stages: the formation of focused streak and the shift of focusing position. It is also found that the channel structures with small radii are dominant during the whole inertial focusing process. A three-stage model is then presented to elucidate the flow-rate regulation mechanism in terms of the competition between inertial lift force and Dean drag force, according to the evolution of particle focusing dynamics with increasing flow rates. By making comparisons of focusing position and focusing ratio between two different-sized particles under various experimental conditions, we find that the larger particles have better focusing performances and stabilities, and the relative focusing position of different-sized particles can be adjusted by changing the driving flow rate. Finally, the applicability of the explored inertial focusing mechanisms for manipulating biological particles with complex features is investigated by analyzing the lateral migration behaviors of blood cells in the asymmetrically curved microchannel. The obtained conclusions are very important for understanding the particle focusing dynamics in micro-scale flows and developing the point-of-care diagnostic instruments.

Experimental and numerical evidence for the existence of wide and deep phononic gaps induced by inertial amplification in two-dimensional solid structures

The aim of this paper is to show that a two-dimensional periodic solid structure with embedded inertial amplification mechanisms can possess a wide and deep phononic gap at low frequencies. The width and depth of the inertial amplification induced phononic gaps (stop bands) are determined both analytically using a distributed parameter model and numerically using one-dimensional (1D) and two-dimensional (2D) finite element models. The inertial amplification mechanisms are optimized to yield wide and deep gaps at low frequencies. These optimized mechanisms are used to form one- and two-dimensional periodic structures. Frequency responses of these periodic structures are obtained numerically using 1D and 2D finite element models. A deeper gap is generated with the two-dimensional periodic structure when compared with the one-dimensional periodic structure that has the same number of unit cells along the excitation direction. Then, the two-dimensional periodic structure is manufactured and its frequency response is determined via experimental modal analysis. The experimental and numerical frequency response results match quite well, which validate that the two-dimensional periodic solid structure has a wide and deep phononic gap.

Phononic gaps induced by inertial amplification in BCC and FCC lattices

Abstract In this study, infinite and finite periodic body centered cubic (BCC) and face centered cubic (FCC) lattices with and without inertial amplification mechanisms are investigated. These three-dimensional lattices are modeled with mass and spring elements that are parametrically varied to observe their effect on phononic gap (stop band) limits. When inertial amplification mechanisms are used in both of the infinite periodic lattices, wide low frequency band gaps are generated. Moreover, wide and deep phononic gaps are obtained by using moderate amount of unit cells in the case of finite periodic lattices.

Carhart’s notch: A window into mechanisms of bone-conducted hearing

Otosclerosis is a disease process of the ear that stiffens the stapes annular ligament and results in footplate immobilization. This produces a characteristic loss in bone-conducted (BC) hearing of about 20 dB between 1 and 2 kHz, known as “Carhart’s notch,” for which the specific mechanisms responsible have not yet been well understood. In this study, it is hypothesized that this observed pattern of hearing loss results from interactions between compressional and inertial mechanisms of BC hearing. Differences in the basilar-membrane velocity between a normal and otosclerotic human ear were calculated in response to compressional vibration of the cochlear capsule, translational vibration of the skull bone in various directions, and combinations of the two, using an anatomically accurate 3-D finite element model of the middle ear, cochlea, and semicircular canals. Compressional and inertial BC stimuli were found to both be necessary to capture the full behavior of clinical data, with the compressional component dominating below 0.75 kHz, the inertial component dominating above 3 kHz, and the notch between 1 and 2 kHz resulting from the suppression of an ossicular resonance due to stapes fixation. [Work supported by grant R01-DC07910 and R01-DC05960 from the NIDCD of NIH.]

Species traits and inertial deposition of fungal spores

One of the most common classes of bio-aerosols is fungal spores. While there is considerable species-specific variation in the morphological traits of fungal spores, their effect on spore dispersal is not well understood. Due to their super micron size, fungal spores deposit via inertial mechanisms. In this study, we combine experimental, theoretical, and statistical approaches to investigate the effects of spore morphology, airflow conditions, and surface structure on dry deposition of spores of forest-dwelling basidiomycete fungi. Firstly, we measured the spore aerodynamic diameter (Da) of 66 species and spore equivalent diameter (De) of 37 species. De combined with spore wall thickness was the best predictor of Da. We also derived a parameterization to calculate the spore density (ρspore); it ranged between 0.51 and 3.92g/cm3 (mean 1.57g/cm3). Assuming that spores are prolate-ellipsoids and using calculated values of De instead of the measured ones would under estimate ρspore. Secondly, we measured the inertial deposition of spores for 21 species in an experimental setup where spores were carried by turbulent airflow through a vertical pipe containing an obstacle (spruce twigs or a metal mesh). The deposition velocity on spruce twigs was 0.4–21mm/s depending on the airflow velocity, spore size, and twig density. Evaluations of a three-layer deposition model suggested that the roughness length (F) of the twigs was 10–93μm and it depended on the friction velocity. The deposition velocity of spores on the metal mesh was 24–53 times higher than that on the twigs. Spore shape did not have an unambiguous effect on Da or deposition on the mesh. Our study will facilitate the development of mechanistic dispersal models that incorporate the effect of species-specific spore traits as well as a physically realistic description of deposition to environmental surfaces.

Collision of a small rising bubble with a large falling particle

The attachment of bubbles onto a collecting surface plays a critical role in flotation which is utilised for the separation of mineral ores, coal or plastic materials. While mineral flotation deals with fine particles and larger bubbles, this work is focused on the opposite case of an interaction of a single rising bubble (Db<1mm) with a larger spherical particle, which falls down through a stagnant liquid. The collision is studied theoretically and experimentally. The theoretical model, based on an analysis of forces acting on the bubble, leads to a differential equation for the bubble motion. Both the mobile and immobile bubble surfaces are considered. The experimental bubble trajectory and velocity evolution are in good agreement with the theoretical model. The horizontal deflection of the bubble trajectory caused by the particle motion is dependent on the ratio of bubble terminal velocity and particle settling velocity. The influence of buoyancy, interception and inertial mechanisms on the collision efficiency is also examined. It is concluded that the buoyancy is the most significant mechanism for the interaction of small bubbles with large particles.

Generation of magnetic-field perturbations in underwater explosion

In this paper we study the inertial and induction mechanisms of electric-current generation in sea-water motions. The problem of calculating the magnetic field induced by these currents is considered. For the induction generation mechanism, if self-induction is disregarded, the fields arising in central-symmetric motions of sea water (like underwater explosions) are calculated.

10.1007/s11486-008-1006-1

A review of studies devoted to the problem of exciting magnetic signals in the crust associated with the formation of the major rupture in an earthquake source and with the propagation of seismic waves was given in [Sgrigna et al., 2004]. However, this review contains incorrect citations from original papers and several erroneous statements concerning inertial and inductive mechanisms of conversion of the energy of rock motion into magnetic field energy. These mistakes are analyzed in the present paper. The formal and physical similarity between seismomagnetic waves in the crust and Alfvén waves in the magnetosphere is used in the analysis. A comparative analysis of the inertial and inductive mechanisms of seismomagnetic field generation is performed. The Cherenkov criterion of Alfvén wave generation due to the ionospheric effect of acoustic waves from earthquakes and explosions is derived. Attention is also given to nonlinear phenomena (nonlinearity of a mechanomagnetic conversion in the crust and anharmonicity and self-focusing of Alfvén waves in the magnetosphere).

Modeling of local particle accumulation in disperse flows with kinematic singularities

AbstractThe aim of the study is to model the formation of local particle accumulation zones near several typical kinematic singularities. The flows considered are: (i) a steady two–dimensional flow with localized vorticity of the Kelvin cat's eye type (vortex in a mixing layer), (ii) a steady axisymmetric flow formed by a vortex filament normal to a plane in viscous fluid (simple model of tornado), (iii) a neighbourhood of a zero acceleration point in two–dimensional unsteady (harmonic) flow. From parametric numerical calculations, we investigated the inertial mechanisms of forming local particle accumulation zones and found the threshold values of governing parameters separating qualitatively different particle velocity and density patterns. In particular, it is shown that the zero–acceleration point can either “attract” or “scatter” the particles. Zones of concentrated vorticity are typically devoid of particles. In the tornado–like flow, an axisymmetric “cup‐shaped” particle accumulation region is formed. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Numerical predictions of submicrometer aerosol deposition in the nasal cavity using a novel drift flux approach

Evaluating the health effects of inhaled submicrometer aerosols, such as combustion particulate matter and bioaerosols, requires a thorough understanding of transport and deposition in the nasal airway. However, numerical simulations of fine respiratory aerosols (100–1000 nm) remain challenging due to low deposition fractions and the action of concurrent inertial and diffusive deposition mechanisms. The objective of this study was to evaluate the transport and deposition of submicrometer aerosols in the nasal cavity based on a novel drift flux model with a near-wall velocity correction (DF-VC), which accounts for the effects of particle inertia and diffusion. Deposition results were also obtained for a commonly implemented chemical species (CS) model that only accounts for particle diffusion. The nasal cavity geometry was developed based on available MRI data, which has also been used in the previous experimental studies. Particle sizes ranging from 1 nm through 1000 nm and inhalations flow rates covering 4–30 L/min were considered. Under these conditions, turbulence only appeared significant in the nasal vestibule-valve region and the dorsal portion of the nasopharynx. In contrast, most of the main nasal passage appeared to have primarily laminar flow. Simulation results of the novel DF-VC model were shown to provide a good match to experimental deposition values from various nasal replica casts, and corroborated an existing empirical correlation for in vivo nasal deposition of submicrometer aerosols. Comparisons of the DF-VC and CS models indicated that inertial effects began to significantly influence total deposition in the nasal cavity at particle Stokes numbers greater than a critical value of St k = 1.0 × 10 −5, which is equivalent to a 90 nm particle under resting conditions and a 50 nm aerosol during moderate activity. A new correlation for mass transfer and deposition in the nasal airways was proposed that accounts for both inertial and diffusional deposition mechanisms and can be applied for all submicrometer aerosols. Results of this study indicate that a drift flux particle transport model with near-wall velocity corrections can provide an effective approach in simulating the transport and deposition of submicrometer respiratory aerosols in human nasal airways.

Inertial effects in the Earth’s crust and magnetosphere

A review of studies devoted to the problem of exciting magnetic signals in the crust associated with the formation of the major rupture in an earthquake source and with the propagation of seismic waves was given in [Sgrigna et al., 2004]. However, this review contains incorrect citations from original papers and several erroneous statements concerning inertial and inductive mechanisms of conversion of the energy of rock motion into magnetic field energy. These mistakes are analyzed in the present paper. The formal and physical similarity between seismomagnetic waves in the crust and Alfven waves in the magnetosphere is used in the analysis. A comparative analysis of the inertial and inductive mechanisms of seismomagnetic field generation is performed. The Cherenkov criterion of Alfven wave generation due to the ionospheric effect of acoustic waves from earthquakes and explosions is derived. Attention is also given to nonlinear phenomena (nonlinearity of a mechanomagnetic conversion in the crust and anharmonicity and self-focusing of Alfven waves in the magnetosphere).

Numerical and experimental deposition of fine respiratory aerosols: Development of a two-phase drift flux model with near-wall velocity corrections

Simulations of fine aerosols (100 nm ⩽ d p ⩽ 1 μ m ) in the respiratory tract are challenging due to low particle deposition rates and the combined effects of diffusional and inertial deposition mechanisms. Furthermore, validations of fine respiratory aerosol deposition are difficult due to a lack of localized experimental data. The objective of this study is to develop and test a continuous two-phase model for simulating the regional and local deposition of dilute fine aerosols in an idealized double bifurcation segment of the respiratory tract. To evaluate the developed transport model, novel in vitro deposition results for 400 nm particles have been determined in a double bifurcation geometry of respiratory generations G3–G5. In addition, previously reported local deposition characteristics for 1 μ m aerosols have also been considered. Computational two-phase models that have been evaluated include a standard chemical species (CS) mass fraction approximation, the drift flux (DF) approach to account for finite particle inertia, and two novel extensions of the DF model to correct for near-wall particle velocity. The first velocity correction model (DF-VC1) applies a continuous field solution for particle slip at the wall surface. As an alternative, a sub-grid near-wall Lagrangian solution has been proposed as the DF-VC2 model. Localized experimental results for the deposition of 400 nm particles indicated elevated deposition contours ranging from 1% to 5% of total deposition at the first bifurcation and 0.1–1% at the second. Of the computational models tested, the DF-VC2 method provided the best match to experimental deposition values on a regional and highly localized basis. Specifically, the DF-VC2 model matched total experimental deposition results to within 10% for both 400 nm and 1 μ m particles. Considering the local deposition of fine aerosols, the DF-VC2 model matched the experimentally determined elevated contours at the first and second bifurcations for both 400 nm and 1 μ m particles. In conclusion, a DF particle transport model with near-wall velocity corrections appears to provide a highly effective solution for the deposition of fine respiratory aerosols.

Assimilation of Interorganizational Business Process Standards

Organizations have not fully realized the benefits of interorganizational relationships (IORs) due to the lack of cross-enterprise process integration capabilities. Recently, interorganizational business process standards (IBPS) enabled by information technology (IT) have been suggested as a solution to help organizations overcome this problem. Drawing on three theoretical perspectives, i.e., the relational view of the firm, institutional theory, and organizational inertia theory, we propose three mechanisms—relational, influence, and inertial—to explain the assimilation of IBPS in organizations. We theorize that these mechanisms will have differential effects on the assimilation of IBPS in dominant and nondominant firms. Using a cross-case analysis based on data from 11 firms in the high-tech industry, we found evidence to support our propositions that relational depth, relationship extendability, and normative pressure were important for dominant firms while relational specificity and influence mechanisms (coercive, mimetic, and normative pressures) were important for nondominant firms. Inertial mechanisms, i.e., ability and willingness to overcome resource and routine rigidities, were important for both dominant and nondominant firms.

Measuring felt recoil of sporting arms

For competitors in the shooting sports, gun recoil can affect performance and create discomfort. An objective method of measuring felt recoil forces would be useful to evaluate methods of recoil reduction. An experimental test apparatus was developed to measure recoil forces of sporting rifles and shotguns. No modifications to the firearms themselves were necessary to make the measurements. Through both inertial and dissipative restraint mechanisms, the apparatus reproduced gun movement that was representative of that experienced by a particular shooter. This should result in measured recoil forces similar to those experienced by the shooter. The apparatus measures the horizontal shoulder force and the vertical force component exerted at the stock comb. The recoil event was found to be quite short, having duration on the order of 10 ms. Peak recoil forces for common shotgun target loads were in the range of 1.6–2.2 kN (360–494 lb f). The apparatus was found sensitive enough to measure recoil force differences among different factory loaded ammunition, and differences in recoil force imparted by different firearms shooting the same ammunition. The apparatus should prove useful for quantifying differences in felt recoil as affected by ammunition type, gunstock geometry, barrel porting, recoil reduction devices, and gun weight, among other factors.

Turbulent inertial gelation and acoustic quasi-gelation of submicron aerosol particles

Inertial turbulent and acoustic orthokinetic particle coagulation mechanisms have physical similarity. We consider analytically and numerically coagulation of discrete compact and fractal submicron agglomerated particles, governed by these mechanisms via Smoluchowski equation. Existence of the inertial turbulent coagulation is mathematically proven. A new gelation scenario is revealed for both of the above coagulation mechanisms. Turbulent inertial gelation is manifested by means of a multi-modal relay-type run-away particle size growth, including formation of infinite set of secondary maxima in volume fraction distribution. When acoustic coagulation mechanism is much stronger than the Brownian coagulation, acoustic coagulation occurs as a quasi-gelation process, with a run-away particle size growth, characterized, however, by a finite set of secondary maxima. The effect of acoustic field on coagulation is shown to be more pronounced for fractal agglomerates than that for compact agglomerated particles.

Inertial deposition of nanoparticle chain aggregates: Theory and comparison with impactor data for ultrafine atmospheric aerosols

Nanoparticle chain aggregates (NCAs) are often sized and collected using instruments that rely on inertial transport mechanisms. The instruments size segregate aggregates according to the diameter of a sphere with the same aerodynamic behavior in a mechanical force field. A new method of interpreting the aerodynamic diameter of NCAs is described. The method can be used to calculate aggregate surface area or volume. This is useful since inertial instruments are normally calibrated for spheres, and the calibrations cannot be directly used to calculate aggregate properties. A linear relationship between aggregate aerodynamic diameter and primary particle diameter based on published Monte-Carlo drag calculations is derived. The relationship shows that the aggregate aerodynamic diameter is independent of the number of primary particles that compose an aggregate, hence the aggregate mass. The analysis applies to aggregates with low fractal dimension and uniform primary particle diameter. This is often a reasonable approximation for the morphology of nanoparticles generated in high temperature gases. An analogy is the use of the sphere as an approximation for compact particles. The analysis is applied to the collection of NCAs by a low-pressure impactor. Our results indicate the low-pressure impactor collects aggregates with a known surface area per unit volume on each stage. Combustion processes often produce particles with aggregate structure. For diesel exhaust aggregates, the surface area per unit volume calculated by our method was about twice that of spheres with diameter equal to the aerodynamic diameter. Measurements of aggregates collected near a major freeway and at Los Angeles International Airport (LAX) were made for two aerodynamic cutoff diameter diameters (d a,50), 50 and 75 nm. (Aerodynamic cutoff diameter refers to the diameter of particles collected with 50% efficiency on a low-pressure impactor stage.) Near-freeway aggregates were probably primarily a mixture of diesel and internal combustion engine emissions. Aggregates collected at LAX were most likely present as a result of aircraft emissions. In both measurements, the aggregate aerodynamic diameters calculated from the primary particle diameter were fairly close to the stage cutoff diameter. The number of primary particles per aggregate varied one order of magnitude for particles depositing on the same stage. The average aggregate surface area per unit volume was 2.41 × 106 cm−1 and 2.59 × 106 cm−1 (50 nm d a,50) and 1.81 × 106 cm−1 and 1.68 × 106 cm−1 (75 nm d a,50) for near-freeway and LAX measurements, respectively. These preliminary measurements are consistent with values calculated from theory.

Hydraulic tests in highly permeable aquifers

A semianalytical solution is presented for a mathematical model describing the flow of groundwater in response to a slug or pumping test in a highly permeable, confined aquifer. This solution, which is appropriate for wells of any degree of penetration and incorporates inertial mechanisms at both the test and observation wells, can be used to gain new insights into hydraulic tests in highly permeable settings. The oscillatory character of slug‐ and pumping‐induced responses will vary considerably across a site, even in an essentially homogeneous formation, when wells of different radii, depths, and screen lengths are used. Thus variations in the oscillatory character of responses do not necessarily indicate variations in hydraulic conductivity (K). Existing models for slug tests in partially penetrating wells in high‐K aquifers neglect the storage properties of the media. That assumption, however, appears reasonable for a wide range of common conditions. Unlike in less permeable formations, drawdown at an observation well in a high‐K aquifer will be affected by head losses in the pumping well. Those losses, which affect the form of the pumping‐induced oscillations, can be difficult to characterize. Thus analyses of observation‐well drawdown should utilize data from the period after the oscillations have dissipated whenever possible. Although inertial mechanisms can have a large impact on early‐time drawdown, that impact decreases rapidly with duration of pumping and distance to the observation well. Conventional methods that do not consider inertial mechanisms should therefore be viable options for the analysis of drawdown data at moderate to large times.