Effect Of Particle Inertia Research Articles

Sea surface drag and the role of spray

AbstractMotivated by the possible effects of spray on the drag felt by the ocean surface in high winds, we use direct numerical simulation coupled with Lagrangian particle tracking to investigate how suspended inertial particles alter momentum flux in an idealized turbulent flow. Turbulent Couette flow is used for this purpose since the momentum flux profile is constant across the domain height; a characteristic similar to the constant‐flux layer in the atmospheric surface layer. The simulations show that when inertial particles are introduced into a turbulent flow, they carry a portion of the total vertical momentum flux, and that this contribution can be significant when the particle concentration is sufficiently large. The numerical setup is also used to evaluate a dispersed phase model that treats spray effects as equivalent to an increase in stable atmospheric stratification. Our simulations suggest that in the range of droplet sizes typically found near the air‐sea interface, particle inertial effects dominate any particle‐induced stratification effects.

Magnetic-Induced Migration in a Sedimenting Suspension of Magnetic Spherical Particles

We study the relative trajectories of two magnetic spheres interacting in a dilute suspension in the presence of particle inertia and Brownian motion effect. The particles settle relative to one another under the action of gravity and when in close contact they exert on each other a magnetic force and torque due to a permanent magnetization. The balance equations of forces and torques for the two particles are considered in the present formulation. The numerical simulations are based on direct computations of the hydrodynamic and the magnetic interactions among the rigid spheres in the regime of no-null Stokes number. The behavior of these suspensions is examined based on the relative trajectories calculated for several initial configurations. The calculations show that fluctuations in particle orientation produced by the continuous magnetic interactions and by the Brownian motion exerts a significant effect on the understanding of particle aggregation and particle migration in magnetic suspensions.

A fully Eulerian approach to particle inertial deposition in a physiologically realistic bifurcation

The investigation of aerosol flows in bifurcations is significant in biomedical applications, because this geometry resembles the branching airways of the lung. Most of the existing computational studies regarding aerosol flow in branching airways use Lagrangian description for the particulate phase, when particle inertial effects are taken into consideration. In the present study a fully Eulerian model is used for studying the transport and deposition of inertial particles under steady state inspiratory flow in the single physiologically realistic bifurcation created by generations G3-G4 of the human lung. In-house codes are used to create the geometry and the computational grid, obtain the fluid flow field and calculate particle concentration. Deposition fractions are calculated, concentration profiles are shown and deposition sites are indicated under different flow conditions (Reynolds number and flow asymmetry in the branches) and particles of various sizes (1–10μm). It is found that total particle deposition fraction is loosely dependent on fluid flow Reynolds number and our results are in agreement with experimental findings. Moreover, total deposition fraction does not change significantly between symmetric Q1/Q2=1 and asymmetric Q1/Q2=2 flow conditions, but is considerably lower for the totally obstructed case, Q2=0. On the contrary, deposition sites and particle concentration profiles depend on the various flow conditions. Apart from deposition at the bifurcation, which is present at all cases, deposition sites downstream the bifurcation move towards the outer bifurcation wall and daughter tube exit as Reynolds number increases. For the Q2=0, it is also shown that particles are trapped and deposit even in the obstructed daughter tube. In all studied cases, it is found that there is a particle-free region at the outer wall, at the beginning of the daughter tubes opposite the bifurcation. The straightforward formulation of deposition modelling and derivation of detailed concentration profiles along the bifurcation are major advantages of the fully Eulerian methodology used in the study.

Direct numerical simulation of inertial particle entrainment in a shearless mixing layer

AbstractWe present the first computational study of the dynamics of inertial particles in a shearless turbulence mixing layer. We parametrize our direct numerical simulations to isolate the effects of turbulence, Reynolds number, particle inertia, and gravity on the entrainment process. By analysing particle concentrations, particle and fluid velocities, particle size distributions, and higher-order velocity moments, we explore the impact of particle inertia and gravity on the mechanism of turbulent mixing. We neglect thermodynamic processes, including phase changes between the drops and surrounding air, which is equivalent to assuming the air is saturated (i.e. 100 % humidity). Entrainment is found to be governed by the large scales of the flow and is relatively insensitive to the Reynolds number over the range considered. Our results show that both fluid and particle velocities exhibit intermittency and that gravity and turbulent diffusion interact in unexpected ways to dictate particle dynamics. An analysis of the temporal evolution of fluid and particle statistics suggests that particle concentration profiles and velocities are self-similar under certain circumstances. We also observe large fluctuations in particle concentrations resulting from entrainment and introduce a model to estimate the impact these fluctuations have on the radial distribution function, a statistic that is often used to quantify inertial particle clustering. Our study is both a computational counterpart to and an extension of the wind tunnel experiments by Gerashchenko, Good & Warhaft (J. Fluid Mech., vol. 668, 2011, pp. 293–303) and Good, Gerashchenko, & Warhaft (J. Fluid Mech., vol. 694, 2012, pp. 371–398). We find good agreement between these experimental studies and our computational results. We anticipate that a better understanding of the role of gravity and turbulence in inertial particle entrainment will lead to improved cloud evolution predictions.

Competing effects of particle and medium inertia on particle diffusion in viscoelastic materials, and their ramifications for passive microrheology

We analyze the appropriate form for the generalized Stokes-Einstein relation (GSER) for viscoelastic solids and fluids when bead inertia and medium inertia are taken into account, which we call the inertial GSER. It was previously shown for Maxwell fluids that the Basset (or Boussinesq) force arising from medium inertia can act purely dissipatively at high frequencies, where elasticity of the medium is dominant. In order to elucidate the cause of this counterintuitive result, we consider Brownian motion in a purely elastic solid where ordinary Stokes-type dissipation is not possible. The fluctuation-dissipation theorem requires the presence of a dissipative mechanism for the particle to experience fluctuating Brownian forces in a purely elastic solid. We show that the mechanism for such dissipation arises from the radiation of elastic waves toward the system boundaries. The frictional force associated with this mechanism is the Basset force, and it exists only when medium inertia is taken into consideration in the analysis of such a system. We consider first a one-dimensional harmonic lattice where all terms in the generalized Langevin equation--i.e., the elastic term, the memory kernel, and Brownian forces-can be found analytically from projection-operator methods. We show that the dissipation is purely from radiation of elastic waves. A similar analysis is made on a particle in a continuum, three-dimensional purely elastic solid, where the memory kernel is determined from continuum mechanics. Again, dissipation arises only from radiation of elastic shear waves toward infinite boundaries when medium inertia is taken into account. If the medium is a viscoelastic solid, Stokes-type dissipation is possible in addition to radiational dissipation so that the wave decays at the penetration depth. Inertial motion of the bead couples with the elasticity of the viscoelastic material, resulting in a possible resonant oscillation of the mean-square displacement (MSD) of the bead. On the other hand, medium inertia (the Basset force) tends to attenuate the oscillations by the dissipation mechanism described above. Thus competition between bead inertia and medium inertia determines whether or not the MSD oscillates. We find that, if the medium density is larger than 4/7 of the bead density, the Basset damping will suppress oscillations in the MSD; this criterion is sufficient but not necessary to present oscillations.

A Lagrangian particle random walk model for hybrid RANS/LES turbulent flows

A continuous random walk (CRW) turbulent diffusion model was adapted for Lagrangian particles within gas flowfields simulated by hybrid RANS/LES methodologies. The methodology was designed to model all the particle diffusion in RANS regions and model only the sub-grid diffusion in LES regions. In the RANS approach, the mean flowfield and the turbulent time- and length-scales are obtained with a k–ω (Menter SST) turbulence model. These values are used with a discrete stochastic equation to compute instantaneous gas velocity along an individual particle trajectory. Experimental results for turbulent diffusion of particles in a homogeneous wake flow were first used to calibrate the RANS model. The stochastic diffusion model was then extended to utilize the Nichols–Nelson k–ω hybrid RANS/LES turbulence model in the unsteady three-dimensional wake of a cylinder. In particular, the flow at a Mach number of 0.1 and Reynolds number (ReD) of 800 was computed with a 5th-order upwind-biased scheme. The discrete stochastic equation was used to compute sub-grid fluctuations, which could be added to the resolved velocity field, and specifically took into account combined effects of particle inertia and non-homogeneous turbulence. The combination of resolved diffusion and sub-grid diffusion compared quite reasonably with diffusion based on Direct Numerical Simulation of the Navier–Stokes equations. The results indicate that eddy-crossing effects and inertia-based drift corrections can be critical, even when most of the kinetic energy is captured with the resolved-scales of an LES approach.

Numerical and experimental investigation of lubricating oil flow in a gerotor pump

Gerotor pumps are widely used in the automotive industry for engine oil lubrication, due to their high volumetric efficiency and smooth pumping action. In many cases, the lubricating oil from the sump is mixed with contaminants, such as dust and tiny solid particles, or becomes thickened, due to aging. These problems will lead to critical situations, such as increased noise, enhanced wear and erosion, and poor lubrication of the engine. These critical situations were studied by conducting a detailed CFD integrated investigation on a gerotor pump’s performance at different operating conditions in three phases, and the results are presented in this paper. In first phase, a CFD model of a gerotor pump was developed with a dynamic mesh for the rotary movement of both the inner and outer rotors. The effects on pump flow rate of important parameters, such as rotor speed, fluid viscosity and number of ports, were simulated using non-contaminated oil at room temperature and an elevated temperature of 140oC. The relationship between flow rate and pressure at different rotor speeds was predicted and validated with test data for further parametric study. The pressure ripples at different time steps were measured at different angular positions of the rotors to examine the model accuracy. It was found that the flow rate increased and pressure pulsation, as well as flow recirculation, was reduced when ports were added to the cover plate. A suction pipe with a strainer was added for the second phase to capture the undesired changes in flow behavior, such as cavitation, which is caused by negative suction at the inlet region of pump. A suitable size for the inlet suction pipe for this pump was chosen after performing tests to characterize the flow behavior with single and double ports. Next, the relationship between pressure drop and strainer porosity was determined using different porosity values for the strainers. In the final phase, oil with different concentrations of solids was simulated to measure the effect of solid particles on flow rates and pressure losses. It was observed that the intensity of the recirculation was reduced at the suction end at the higher concentration of 0.04%, due to particle inertial effects. It was also found that particle size distribution affected the overall efficiency and pressure head of the pump.

Distribution characteristics of exhaust gases and soot particles in a wall-flow ceramics filter

An inhomogeneous soot distribution in a diesel particulate filter may deteriorate its behavior and result in higher pressure drops and fuel consumption. This will cause mechanical stresses on the filter due to temperature gradients resulting from the non-uniformly burning of soot during regeneration. The purpose of this paper is to investigate the flow distribution of the exhaust gas entering into a diesel particulate filter, the turbulent motion of diesel soot particles in the inlet header, and their deposition and distribution in the front surface of a diesel particulate filter. A Lagranian continuous random walk (CRW) model is developed to simulate soot particulate motion, which considers a succession of uncorrelated random forcing and drift corrections. The effects of particle inertia, turbulent fluctuation, and lift on the particle motion and trajectory are analyzed. Correlations of the uniformity index of the exhaust gas and soot particles with the flow rate, soot loading, and inlet expansion angle are evaluated. The results show that there is a two-peak phenomenon in the soot distribution at the front entrance of the filter, which is comprised of a peak in the central area due to inertia and a second peak in the periphery owing to diffusion and recirculation action. Exhaust flow rates and the inlet expansion angle have a major influence on the flow uniformity and soot uniformity, while soot loading has a slightly smaller effect on soot uniformity.

The effect of particle inertia on triaxial ellipsoids in creeping shear: From drift toward chaos to a single periodic solution

The motion of inertial, triaxial ellipsoids in creeping shear flow is explained for a wide range of aspect ratios and Stokes numbers (St, quantifying particle inertia). Particle inertia induces a drift toward rotation around the shortest axis, with this axis aligned with the vorticity axis of the flow. For aspect ratio combinations in a certain region, this periodic state is unstable for low St and the particle moves in a chaotic manner. At higher St, the instability is stabilized and one single final periodic motion is well defined also for (in the limit of St=0) unstable aspect ratios.

A numerical investigation of fine particle laden flow in an oscillatory channel: the role of particle-induced density stratification

Studying particle-laden oscillatory channel flow constitutes an important step towards understanding practical application. This study aims to take a step forward in our understanding of the role of turbulence on fine-particle transport in an oscillatory channel and the back effect of fine particles on turbulence modulation using an Eulerian–Eulerian framework. In particular, simulations presented in this study are selected to investigate wave-induced fine sediment transport processes in a typical coastal setting. Our modelling framework is based on a simplified two-way coupled formulation that is accurate for particles of small Stokes number (St). As a first step, the instantaneous particle velocity is calculated as the superposition of the local fluid velocity and the particle settling velocity while the higher-order particle inertia effect neglected. Correspondingly, only the modulation of carrier flow is due to particle-induced density stratification quantified by the bulk Richardson number, Ri. In this paper, we fixed the Reynolds number to be ReΔ = 1000 and varied the bulk Richardson number over a range (Ri = 0, 1 × 10−4, 3 × 10−4 and 6 × 10−4). The simulation results reveal critical processes due to different degrees of the particle–turbulence interaction. Essentially, four different regimes of particle transport for the given ReΔ are observed: (i) the regime where virtually no turbulence modulation in the case of very dilute condition, i.e. Ri ~ 0; (ii) slightly modified regime where slight turbulence attenuation is observed near the top of the oscillatory boundary layer. However, in this regime a significant change can be observed in the concentration profile with the formation of a lutocline; (iii) regime where flow laminarization occurs during the peak flow, followed by shear instability during the flow reversal. A significant reduction in the oscillatory boundary layer thickness is also observed; (iv) complete laminarization due to strong particle-induced stable density stratification.

A model for predicting the acceleration variance of arbitrary-density finite-size particles in isotropic turbulence

The paper concerns the effects of particle inertia, density, and size on acceleration statistics. A simple analytical model for estimating the acceleration variance of particles suspended in an isotropic homogeneous turbulent flow field is developed. This model is capable of qualitative describing the particle acceleration variance over the entire range of the particle-to-fluid density ratio. Comparisons of model predictions with numerical simulations and experimental data are presented.

A stochastic jump diffusion particle‐tracking model (SJD‐PTM) for sediment transport in open channel flows

A stochastic jump diffusion (SJD) process is used to describe movement of sediment particles in open channel flows. The stochastic jump diffusion particle‐tracking model (SJD‐PTM) is governed by the stochastic differential equation (SDE). The SDE consists of three main terms including a mean drift motion term, a Wiener process representing random turbulent motion, and a Poisson process describing the abrupt movement of particles caused by probabilistic occurrences of the extreme flow perturbations. The proposed SJD‐PTM can characterize the probabilistic properties of sediment particle movement by simulating the most probable trajectory and ensemble variances of particle movement associated with both flow turbulence and random occurrences of extreme flow perturbations. For the particle movement in response to extreme flow occurrences, we have introduced the particle relaxation time (temporal lag) to quantify the delayed response of sediment particles to large flow perturbations because of the particle inertia effect. The particle relaxation time is derived from a consideration of the forces exerted on particles under the effect of flow accelerations. The particle relaxation time is demonstrated to be dependent on particle size and density as well as the particle Reynolds number. The impact of drag and added mass forces on the ensemble mean and variance of particle trajectory is also evaluated. The particle relaxation time is found to be a factor that diminishes the impact of the extreme flow perturbations. It is shown that heavier and larger particles normally have a larger particle relaxation time, a decreased particle jump magnitude and a smaller ensemble variance of particle trajectories in the occurrences of extreme flow perturbations. It is concluded that the proposed SJD‐PTM with the particle relaxation time can better describe the movement of sediment particles of nonnegligible size in response to extreme flow perturbations. The ability to quantify the variances of particle movement more comprehensively is one of the major advantages associated with the SJD‐PTM for longer‐term sediment transport modeling and predictions. The proposed SJD‐PTM is verified against two distinct experimental data.

Non-linear evolution of the diocotron instability in a pulsar electrosphere: two-dimensional particle-in-cell simulations

<i>Context. <i/>The physics of the pulsar magnetosphere near the neutron star surface remains poorly constrained by observations. Indeed, little is known about its emission mechanism, from radio to high-energy X-ray and gamma-rays. Nevertheless, it is believed that large vacuum gaps exist in this magnetosphere, and a non-neutral plasma partially fills the neutron star surroundings to form an electrosphere in differential rotation.<i>Aims. <i/>According to several of our previous works, the equatorial disk in this electrosphere is diocotron and magnetron unstable, at least in the linear regime. To better assess the long term evolution of these instabilities, we study the behavior of the non-neutral plasma using particle simulations.<i>Methods. <i/>We designed a two-dimensional electrostatic particle-in-cell (PIC) code in cylindrical coordinates, solving Poisson equation for the electric potential. In the diocotron regime, the equation of motion for particles obeys the electric drift approximation. As in the linear study, the plasma is confined between two conducting walls. Moreover, in order to simulate a pair cascade in the gaps, we add a source term feeding the plasma with charged particles having the same sign as those already present in the electrosphere.<i>Results. <i/>First we checked our code by looking for the linear development of the diocotron instability in the same regime as the one used in our previous work, for a plasma annulus and for a typical electrosphere with differential rotation. To very good accuracy, we retrieve the same growth rates, supporting the correctness of our PIC code. Next, we consider the long term non-linear evolution of the diocotron instability. We found that particles tend to cluster together to form a small vortex of high charge density rotating around the axis of the cylinder with only little radial excursion of the particles. This grouping of particles generates new low density or even vacuum gaps in the plasma column. Finally, in more general initial configurations, we show that particle injection into the plasma can drastically increase the diffusion of particles across the magnetic field lines. The newly formed vacuum gaps cannot be replenished by simply invoking diocotron instability.<i>Conclusions. <i/>Diocotron instability offers a new possibility to solve the current closure problem in a pulsar magnetosphere. It is a promising mechanism leading to highly unstable flows in the pulsar inner magnetosphere. When flowing towards the light cylinder, some relativistic and particle inertia effects (not included in this study) appear. Nevertheless, the system should remain unstable because of the relativistic diocotron or the magnetron instability. Therefore, we expect an electric current to circulate in the closed magnetosphere and to feed the base of the wind with charged particles.

Reynolds number dependence of gas-phase turbulence in particle-laden flows: Effects of particle inertia and particle loading

A gas-particle flow experiment at a low particle loading ( m = 0.4) in a vertical downward pipe is conducted at three different Reynolds numbers (Re = 6000, 10,000, and 13,000) to investigate the Re influence on the gas-phase turbulence modulation. The mean and fluctuating velocity data of both phases are acquired using a two-component LDV/PDA system. Two particles of varying degrees of inertia (i.e. high-density 70 µm glass beads and low-density 60 µm cenospheres) are used as the model particles to examine the effect of particle inertia on the trend in the turbulence modulation as a function of Re. An experiment at a higher particle loading ( m = 4.0) using the glass beads is also conducted to examine the effect of particle concentration. In the presence of high inertia particles (St T > 500) at a low particle loading, the gas-phase turbulence intensity in the pipe core is increased with increasing Re resulting in turbulence enhancement relative to the unladen flow. The turbulence enhancement is attributed to 1) a modification of the turbulence production by the Reynolds stress due to interparticle collision and/or 2) a reduction in the fluctuating drag force due to a change in the radial profile of the particle concentration. In contrast, the gas-phase turbulence intensity in the presence of low inertia particles (St T < 500) is found to decrease with increasing Re similar to the trend in the unladen flow. Lastly, the turbulence enhancement at high Re is not observed at a high particle loading where the turbulent energy dissipation by the fluctuating drag force is dominant.

Effect of particle clustering on the gravitational settling velocity in homogeneous turbulence

Astatistical model of the gravitational settling velocity of clusters in homogeneous isotropic turbulence is developed. The effects of particle hydrodynamic interaction, inertia, size, and volume fraction on the particle settling velocity component attributable to particle clustering are analyzed.

Shear-induced self-diffusion of inertial particles in a viscous fluid

We propose a theoretical prediction of the self-diffusion tensor of inertial particles embedded in a viscous fluid. The derivation of the model is based on the kinetic theory for granular media including the effects of finite particle inertia and drag. The self-diffusion coefficients are expressed in terms of the components of the kinetic stress tensor in a general formulation. The model is valid from dilute to dense suspensions and its accuracy is verified in a pure shear flow. The theoretical prediction is compared to simulations of discrete particle trajectories assuming Stokes drag and binary collisions. We show that the prediction of the self-diffusion tensor is accurate provided that the kinetic stress components are correctly predicted.

Focused patterning of nanoparticles by controlling electric field induced particle motion

We report a general methodology for producing focused arrays of nanoparticles via electrodynamic focusing approach and controlling the inertial effect of charged aerosols. An important effect of particle inertia is identified and verified by performing detailed calculations of electric field induced particle motion and experimenting with electrosprayed nanoparticles. The controllability of focusing is demonstrated by changing the curvature of electric field lines.

Nanoparticle motion trajectories and deposition in an inlet channel of wall-flow diesel particulate filter

A two-dimensional gas–particle two-phase flow model in an inlet channel of diesel particulate filter (DPF) has been developed. The interaction between the gas and the particle is treated as one-way coupling due to the extremely dilute particle concentration. The drag force, the Brownian excitation, and the partial slip are included in the particle motion equation. The particle motion trajectories for various particle source locations and various particle sizes are presented. The dependences of the velocity field of the channel on wall permeability and upstream velocity are evaluated. The effects of particle size, upstream velocity, wall permeability, Brownian motion, and partial slip on the particle deposition are investigated. The three dominant mechanisms, which are drag force, Brownian motion, and particle inertia, are analyzed deeply. These results demonstrate that the drag force always plays the most primary role in determining the particle motion and deposition. On the other hand, the effects of Brownian motion and particle inertia vary with Pe number and Re p * number, respectively. As Pe number and Re p * number increase, the effect of particle inertia enhances, while the effect of Brownian motion lowers. The predicted velocity field is compared with the results obtained from the classical one-dimensional model, and the computational pressure loss of DPF is compared with the experimental values. The reasonable agreements of the two cases are both observed.

Modeling inertial particle acceleration statistics in isotropic turbulence

Our objective is to explain recent Lagrangian acceleration measurements of inertial particles in decaying, nearly isotropic turbulence [Ayyalasomayajula et al., Phys. Rev. Lett. 97, 144507 (2006)]. These experiments showed that as particle inertial effects increased, the variance in the particle acceleration fluctuations was reduced, and the tails of the normalized particle acceleration probability density function (PDF) became systematically attenuated. We model this phenomenon using a base flow that consists of a two-dimensional array of evenly spaced vortices with signs and intensities that vary randomly in time. We simulate a large sample of inertial particles moving through the fluid without disturbing the flow (one-way coupling). Consistent with Bec et al. [J. Fluid Mech. 550, 349 (2006)], we find that our model exhibits preferential concentration or clustering of particles in regions located away from the vortex centers. That is, inertial particles selectively sample the flow field, oversampling regions with high strains and undersampling regions with high vorticities. At low Stokes numbers, this biased “sampling” of the flow is responsible for the reduction in the acceleration variance and partially explains the attenuation of the tails of the acceleration PDF. However, contrary to previous findings, we show that the tails of the PDF are also diminished by “filtering” induced by the attenuated response of the inertial particles to temporal variations in the fluid acceleration: Inertial particles do not respond to fluctuations with frequencies much higher than the inverse of the particle stopping time. We show that larger fluid acceleration events have higher frequencies and hence experience greater filtering by particle inertia. We contrast the vortex model with previous Lagrangian acceleration models by Sawford [Phys. Fluids A 3, 1577 (1991)] and Reynolds [Phys. Fluids 15, L1 (2003)] and show that although these models capture some aspects of the inertial particle behavior, it is necessary to employ a model of the flow with spatial structure to capture the effect of sampling on the inertial particle dynamics.

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.