Showing papers on "Schmidt number published in 1999"
TL;DR: In this paper, the effect of the Prandtl number on the dynamics of a convective turbulent flow is studied by numerical experiments and three series of experiments have been performed; in two of them the Rayleigh number was set equal to 0.022 (mercury) and 0.7 (air).
Abstract: The effect of Prandtl number on the dynamics of a convective turbulent flow is studied by numerical experiments. In particular, three series of experiments have been performed; in two of them the Rayleigh number spanned about two decades while the Prandtl number was set equal to 0.022 (mercury) and 0.7 (air). In the third series, in contrast, we fixed the Rayleigh number at 6×105 and the Prandtl number was varied from 0.0022 up to 15. The results have shown that, depending on the Prandtl number, there are two distinct flow regimes; in the first (Pr[lsim ]0.35) the flow is dominated by the large-scale recirculation cell that is the most important ‘engine’ for heat transfer. In the second regime, on the other hand, the large-scale flow plays a negligible role in the heat transfer which is mainly transported by the thermal plumes.For the low-Pr regime a model for the heat transfer is derived and the predictions are in qualitative and quantitative agreement with the results of the numerical simulations and of the experiments. All the hypotheses and the consequences of the model are directly checked and all the findings are consistent with the predictions and with experimental observations performed under similar conditions. Finally, in order to stress the effects of the large-scale flow some counter examples are shown in which the large-scale motion is artificially suppressed.
181 citations
TL;DR: In this article, an approximate solution for the steady laminar flow along a semi infinite horizontal plate in the presence of species concentration and chemical reaction has been obtained using Numerical Technique.
Abstract: An approximate solution for the steady laminar flow along a semi infinite horizontal plate in the presence of species concentration and chemical reaction has been obtained using Numerical Technique. It has been observed that in the presence of chemical reaction, (i) the velocity and concentration increase with decrease of Schmidt number Sc. (ii) Skin friction and rate of concentration decrease with the increase of chemical reaction parameter.
151 citations
01 Nov 1999
TL;DR: In this article, the stirring and mixing properties of one-phase coaxial jets, with large outer (annular) to inner velocity ratio ru = u2/u1 are investigated.
Abstract: The stirring and mixing properties of one-phase coaxial jets, with large outer (annular) to inner velocity ratio ru = u2/u1 are investigated. Mixing is contemplated according to its geometrical, statistical and spectral facets with particular attention paid to determining the relevant timescales of the evolution of, for example, the interface area generation between the streams, the emergence of its scale-dependent (fractal) properties and of the mixture composition after the mixing transition. The two key quantities are the vorticity thickness of the outer, fast stream velocity profile which determines the primary shear instability wavelength and the initial size of the lamellar structures peeled-off from the slow jet, and the elongation rate γ = (u2 − u1)/e constructed with the velocity difference between the streams and the gap thickness e of the annular jet. The kinetics of evolution of the interface corrugations, and the rate at which the mixture evolves from the initial segregation towards uniformity is prescribed by γ−1. The mixing time ts, that is the time needed to bring the initial scalar lamellae down to a transverse size where molecular diffusion becomes effective, and the corresponding dissipation scale s(ts) areformula herewhere Re and Sc denote the gap Reynolds number and the Schmidt number, respectively. The persistence of the large-scale straining motion is also apparent from the spectra of the scalar fluctuations which exhibit a k−1 shape on the inertial range of scales.
131 citations
TL;DR: In this paper, the effects of combined buoyancy forces from mass and thermal diffusion by natural convection flow from a vertical wavy surface have been investigated using the implicit finite difference method.
Abstract: In the present paper, effects of combined buoyancy forces from mass and thermal diffusion by natural convection flow from a vertical wavy surface have been investigated using the implicit finite difference method. Here we have focused our attention on the evolution of the surface shear stress,f″(0), rate of heat transfer,g′(0), and surface concentration gradient,h′(0) with effect of different values of the governing parameters, such as the Schmidt number Sc ranging from 7 to 1500 which are appropriate for different species concentration in water (Pr=7.0), the amplitude of the waviness of the surface ranging from 0.0 to 0.4 and the buoyancy parameter,w, ranging from 0.0 to 1.
111 citations
TL;DR: In this article, a round jet injected into a confined crossflow in a rectangular tunnel has been simulated using the Reynolds-averaged Navier-Stokes equations with the standard k-e turbulence model.
103 citations
TL;DR: In this paper, the free convection effect on magnetohydrodynamic heat and mass transfer of a continuously moving permeable vertical surface was considered and the similar equations were solved by using a suitable variable transformation and employing an implicit finite difference method.
72 citations
TL;DR: In this paper, the authors present a review and re-analyzes the historical data and some modeling results for D for Hg vapor in air, N2 and O2 and recasts results of an independent review of dynamic viscosity and thermal conductivity of air in a form that are consistent with one another and with this author's previous study of D for simple gases and air, near STP.
62 citations
TL;DR: In this article, the Lagrangian spectral relaxation (LSR) model is extended to treat turbulent mixing of two passive scalars with different molecular diffusivity coefficients (i.e., differential-diffusion effects).
Abstract: The Lagrangian spectral relaxation (LSR) model is extended to treat turbulent mixing of two passive scalars (φα and φβ) with different molecular diffusivity coefficients (i.e., differential-diffusion effects). Because of the multiscale description employed in the LSR model, the scale dependence of differential-diffusion effects is described explicitly, including the generation of scalar decorrelation at small scales and its backscatter to large scales. The model is validated against DNS data for differential diffusion of Gaussian scalars in forced, isotropic turbulence at four values of the turbulence Reynolds number (Rλ=38, 90, 160, and 230) with and without uniform mean scalar gradients. The explicit Reynolds and Schmidt number dependencies of the model parameters allows for the determination of the Re (integral-scale Reynolds number) and Sc (Schmidt number) scaling of the scalar difference z=φα−φβ. For example, its variance is shown to scale like 〈z2〉∼Re−0.3. The rate of backscatter (βD) from the diffu...
49 citations
TL;DR: In this paper, an analysis is made to determine the heat and mass transfer occurring in the laminar boundary layer on a linearly accelerating surface with temperature dependent heat source subject to suction or blowing.
49 citations
01 Jan 1999
TL;DR: In this article, a numerical particle tracking code has been developed independently in order to predict erosion, corrosion and erosioncorrosion in a three-dimensional square-sectioned U-bend.
Abstract: Erosion-corrosion is accelerated corrosion following the removal of protective films. In the past, the majority of erosion-corrosion research has been undertaken using experimental methods. Today, numerical methods provide researchers with an additional tool for investigation. The CFD code PHOENICS has been used to predict hydrodynamic flow fields in a 180° bend and associated mass transfer rates at high Schmidt numbers (Sc = 520) characteristic for corrosion. The k-e two-equation eddyviscosity model for turbulence has been used. To allow for integration through the viscous sub-layer, the LamBremhorst low Reynolds number damping functions were used. Hydrodynamic flow fields and mass transfer rates have been verified against experimental results. Mass transfer rates were directly converted into corrosion rates assuming oxygen limiting mass transfer control. A numerical particle-tracking code has been developed independently in order to predict erosion. The effect of turbulence on particle motion has been accounted for by the use of an eddy interaction model. Tests have been performed on the particle-tracking code to validate the Eulerian statistics. Two erosion models have been integrated into the code and verified against experimental data. Predictions of erosion, corrosion and erosioncorrosion in a three-dimensional square-sectioned U-bend are presented (Re = 5.67 × 10, Rc / D = 3.35). NOMENCLATURE C concentration of species (mol/m) CR corrosion rate (mm/yr) d mass diffusivity (m/s) Dh width of duct (m) dp particle diameter (m) ER erosion rate (mm/yr) k turbulent kinetic energy (m/s) km mass transfer coefficient (m/s) LE eddy length (m) M molecular mass (kg/kmol) m mass (kg) p fluid pressure (Pa) Q volume (m) Rc radius of curvature (m) Re Reynolds number, Re = ub Dh / ν Sc Schmidt number, Sc = ν / d Sh Sherwood numbers, Sh = km Dh / d Sy Yield strength of material (MPa) t time (s) TE eddy lifetime (s) u velocity (m/s) Greek letters α particle impact angle (degrees) e dissipation of turbulent kinetic energy (m/s) ρ density (kg/m) τ shear stress (kg/ms) ν fluid kinematic viscosity (m/s) μ fluid viscosity (kg/m/s)
28 citations
TL;DR: In this paper, experiments were carried out on a bubble absorber operating as part of a vapour absorption refrigeration system working with HCFC22-DMF to obtain heat and mass transfer and pressure drop data.
TL;DR: In this article, the vorticity-velocity formulation is applied to solve for the coupled momentum, energy and concentration equations for the laminar natural convection heat and mass transfer in open vertical rectangular ducts with uniform wall temperature/uniform wall concentration (UWT/UWC) or uniform heat flux/UNiform mass flux (UHF/UMF) boundary conditions.
TL;DR: In this paper, a combined numerical and theoretical investigation of laminar natural convection heat and mass transfer in open vertical parallel plates with unheated entry and unheat exit is presented.
07 Jun 1999
TL;DR: In this paper, a round jet injected into a confined crossflow in a rectangular tunnel has been simulated using the Reynolds-Averaged Navier-Stokes equations coupled with the standard k-e turbulence model.
Abstract: The adequacy and accuracy of the constant Schmidt number assumption in predicting turbulent scalar fields in jet-in-crossflows are assessed in the present work. A round jet injected into a confined crossflow in a rectangular tunnel has been simulated using the Reynolds-Averaged Navier-Stokes equations coupled with the standard k-e turbulence model. A semi-analytical qualitative analysis was made to guide the selection of Schmidt number values. A series of parametric studies were performed, and Schmidt numbers ranging from 0.2 to 1.5 and jet-to-crossflow momentum flux ratios from 8 to 72 were tested. The principal observation is that the Schmidt number does not have an appreciable effect on the species penetration, but it does have a significant effect on species spreading rate in jet-in-crossflows, especially for the cases where the jet-to-crossflow momentum flux ratios are relatively small. A Schmidt number of 0.2 is recommended for best agreement with data. The limitations of the standard k–e turbulence model and the constant Schmidt number assumption are discussed.Copyright © 1999 by ASME
TL;DR: The Lagrangian direct-interaction approximation developed previously by the present authors [S. Kida and S. Goto as mentioned in this paper is applied to a passive scalar field in isotropic turbulence.
Abstract: The Lagrangian direct-interaction approximation developed previously by the present authors [S. Kida and S. Goto, J. Fluid Mech. 345, 307 (1997)] is applied to a passive scalar field in isotropic turbulence. We examine the behavior of solutions to the resultant closure equations for the correlation function of the scalar field for arbitrary values of the Schmidt number, and show systematically that the solutions are completely consistent with the phenomenological theories on the scalar spectral function by Obukhov (1949), Corrsin (1951), Batchelor et al. (1959), and Batchelor (1959). The universal forms of the function in the statistically stationary state are obtained by solving the closure equations numerically in the whole wave number range for each case of moderate, extremely large, and small values of the Schmidt number.
TL;DR: In this paper, the authors consider the nonlinear spin-up/down of a rotating stratified fluid in a coni-cal container and show good quantitative agreement for positive changes in the rotation rate of the container (relative to the initial rotation sense).
Abstract: We consider the nonlinear spin-up/down of a rotating stratified fluid in a coni-
cal container. An analysis of axisymmetric similarity-type solutions to the relevant
boundary-layer problem, Duck, Foster & Hewitt (1997), has revealed three types of
behaviour for this geometry. In general, the boundary layer evolves to either a steady
state, or a gradually thickening boundary layer, or a finite-time singularity depending
on the Schmidt number, the ratio of initial to final rotation rates, and the relative
importance of rotation and stratification.
In this paper we emphasize the experimental aspects of an investigation into the
initial readjustment process. We make comparisons with the previously presented
boundary-layer theory, showing good quantitative agreement for positive changes
in the rotation rate of the container (relative to the initial rotation sense). The
boundary-layer analysis is shown to be less successful in predicting the flow evolution
for nonlinear decelerations of the container. We discuss the qualitative features of
the spin-down experiments, which, in general, are dominated by non-axisymmetric
effects. The experiments are conducted using salt-stratified solutions, which have a
Schmidt number of approximately 700.
The latter sections of the paper present some stability results for the steady
boundary-layer states. A high degree of non-uniqueness is possible for the system
of steady governing equations; however the experimental results are repeatable and
stability calculations suggest that �higher branch� solutions are, in general, unstable.
The eigenvalue spectrum arising from the linear stability analysis is shown to have
both continuous and discrete components. Some analytical results concerning the
continuous spectrum are presented in an appendix.
A brief appendix completes the previous analysis of Duck, Foster & Hewitt (1997),
presenting numerical evidence of a different form of finite-time singularity available
for a more general boundary-layer problem.
TL;DR: In this article, an analytic model for the impedance response of a rotating disk electrode was presented. But the model was only valid for an infinite Schmidt number and was used as part of a model for radially dependent convective diffusion on impedance response.
Abstract: Frequency-domain techniques are commonly employed in the study of electrode kinetics and mass transfer in electrolytic solutions. While the information obtained is similar to that from transient techniques, better resolution of physical processes can be achieved because the noise level in frequency-domain measurements can be made extremely small. 1-3 A second advantage of the frequency domain techniques over transient techniques is that the KramersKronig relations can be used to identify instrumental artifacts or changes in baseline properties. 4-7 The uniform accessibility of the rotating disk at the mass-transfer-limited current makes it an attractive tool for frequency-domain techniques. Significant effort has been expended on developing analytic formulae for the impedance response of a rotating disk electrode. 8-19 A comparative study of the application of these models to interpretation of impedance spectra has been presented by Orazem et al. 20 A one-dimensional numerical model for the impedance response of a rotating disk electrode which accounted for the influence of a finite Schmidt number was presented by Tribollet and Newman. 21 This model accounts for effects associated with kinetics, mass-transport, and ohmic potential drop within the bulk of the solution under the assumption that the disk can be treated as being uniform. The first two terms in the Cochran 22 expansion for the axial component of fluid velocity were included in the convective diffusion equation. Tribollet et al. 18 reported that the errors in the calculated Schmidt numbers caused by assuming an infinite Schmidt number, i.e., by neglecting the second and higher terms in the axial velocity expansion, could be as high as 24% for a Schmidt number of 1000. This result was confirmed by regression of various masstransfer models to impedance data. 20 Mathematical models have been developed which account for frequency dispersion associated with the nonuniform potential distribution on the disk electrode, 23-26 but to date, no comparable model has been developed for the influence of nonuniform mass transfer on the impedance response. Appel and Newman 27 provided a preliminary mathematical development, valid for an infinite Schmidt number, that could be used as part of a model for the influence of radially dependent convective diffusion on the impedance response. Appel used this approach to calculate the radial distribution of impedance, but results were presented only for a single dimensionless frequency due to numerical difficulties associated with implementation of the model. 28
TL;DR: In this article, a new empirical correlation was developed, with major advances over the commonly used models, without the need of further correlation coefficients that has to be adapted to each experimental setup.
TL;DR: In this paper, the authors proposed an approximate approach for the simplification of the scalar correlation equation for mass transfer coefficient, which is applicable to all mass transfer models, such as the film model, penetration model, and models resulting from boundary layer analyses.
TL;DR: In this article, the authors consider a set of nonlinear boundary-layer equations that have been derived by Duck, Foster and Hewitt (1997a, DFH) for the swirling flow of a linearly stratified fluid in a conical container.
Abstract: We consider a set of nonlinear boundary-layer equations that have been derived by
Duck, Foster & Hewitt (1997a, DFH), for the swirling flow of a linearly stratified
fluid in a conical container. In contrast to the unsteady analysis of DFH, we re-
strict attention to steady solutions and extend the previous discussion further by
allowing the container to both co-rotate and counter-rotate relative to the contained
swirling fluid. The system is governed by three parameters, which are essentially non-
dimensional measures of the rotation, stratification and a Schmidt number. Some of
the properties of this system are related (in some cases rather subtly) to those found
in the swirling flow of a homogeneous fluid above an infinite rotating disk; however,
the introduction of buoyancy effects with a sloping boundary leads to other (new)
behaviours. A general description of the steady solutions to this system proves to be
rather complicated and shows many interesting features, including non-uniqueness,
singular solutions and bifurcation phenomena.
We present a broad description of the steady states with particular emphasis on
boundaries in parameter space beyond which steady states cannot be continued.
A natural extension of this work (motivated by recent experimental results) is to
investigate the possibility of solution branches corresponding to non-axisymmetric
boundary-layer states appearing as bifurcations of the axisymmetric solutions. In
an Appendix we give details of an exact, non-axisymmetric solution to the Navier�
Stokes equations (with axisymmetric boundary conditions) corresponding to the flow
of homogeneous fluid above a rotating disk.
TL;DR: In this article, the authors considered the unsteady natural convection boundary layer flow over a semi-infinite vertical cylinder with combined buoyancy force effects, for the situation in which the surface temperature T′w(x) and C′w (x) are subjected to the power-law surface heat and mass flux as K(T′n) = −axn and D(C′/r) =−bxm.
Abstract: The unsteady natural convection boundary layer flow over a semi-infinite vertical cylinder is considered with combined buoyancy force effects, for the situation in which the surface temperature T′w(x) and C′w(x) are subjected to the power-law surface heat and mass flux as K(T′/r) = −axn and D(C′/r) = −bxm. The governing equations are solved by an implicit finite difference scheme of Crank-Nicolson method. Numerical results are obtained for different values of Prandtl number, Schmidt number ‘n’ and ‘m’. The velocity, temperature and concentration profiles, local and average skin-friction, Nusselt and Sherwood numbers are shown graphically. The local Nusselt and Sherwood number of the present study are compared with the available result and a good agreement is found to exist.
TL;DR: In this article, a stochastic model is employed to simulate the carrier phase of particles in isotropic incompressible turbulence and the results of the simulations are compared with direct numerical simulation (DNS) data and theoretical results.
TL;DR: In this paper, S-doped InP crystals were grown from an In-solution in a THM arrangement during the EURECA-1 mission using the automatic mirror furnace (AMF) under microgravity conditions.
01 Jan 1999
TL;DR: In this paper, a combination of PHOENICS CFD code and the particletracking code predictions of erosion, corrosion and erosion-corrosion in a two-dimensional 180 degree bend and a three-dimensional square-sectioned U-bend are presented.
Abstract: Erosion-corrosion is accelerated corrosion following the removal of protective films. In the past, the majority of erosion-corrosion research has been undertaken using experimental methods. Today, numerical methods provide researchers with an addition tool for investigation. The commercial computational fluid dynamics (CFD) code PHOENICS has been used to predict hydrodynamic flow fields and mass transfer rates at high Schmidt numbers (Sc = 520 and Sc = 1460) characteristic for corrosion. The ktwo-equation eddy-viscosity model for turbulence has been used. To allow for integration through the viscous sub-layer, LamBremhorst low Reynolds number damping functions were used. Hydrodynamic flow fields and mass transfer rates have been verified against experimental results. Mass transfer rates were directly converted into corrosion rates assuming limiting mass transfer control. A numerical particle-tracking code has been developed independently. The effect of turbulence on particle motion has been accounted for by the use of an eddy interaction model. Particle dispersion and tracking tests have been performed on the particle-tracking code to validate the Eulerian statistics. Two erosion models have been integrated into the code and verified against experimental data. Using a combination of the PHOENICS CFD code and the particletracking code predictions of erosion, corrosion and erosion-corrosion in a two-dimensional 180 degree bend and a three-dimensional squaresectioned U-bend are presented (Re = 5.67 × 104, Rc/D = 3.35). The effect of particle inertia (hollow glass, sand and copper particles), Reynolds number (Re = 2.1×104, Re = 5.67×104, Re = 1.0×105) and bend orientation (upwards-facing and downwards-facing) on erosion rates, and the effect of diffusivity (Schmidt number) on mass transfer were investigated.
TL;DR: In this article, the stability of boundary-free shear flow is studied for the case of variable viscosity due to binary diffusion across the shear layer and linear stability analysis is used to examine the effect of a nonuniform concentration profile on the stability.
Abstract: The stability of boundary-free shear flow is studied for the case of variable viscosity due to binary diffusion across the shear layer. This leads to the main difficulty of this investigation, the direct coupling of the momentum and species equations in both the base state calculations as well as the stability analysis. Linear stability analysis is used to examine the effect of a nonuniform concentration profile on the stability of the flow. It is found that for the flow to be stable for all disturbance wave numbers the Reynolds number has to be zero. This is in agreement with constant viscosity free shear flow stability theory. Increasing the magnitude of concentration gradient (increasing the Schmidt number) destabilizes the flow.
01 May 1999
TL;DR: In this paper, an investigation of the stability limits of Enclosed Laminar Flames (ELF) was conducted in the Middeck Glovebox (MGBX) facility on the STS-87 Space Shuttle mission (November to December 1997).
Abstract: An investigation of the stability limits of Enclosed Laminar Flames (ELF) was conducted in the Middeck Glovebox (MGBX) facility on the STS-87 Space Shuttle mission (November to December 1997). The primary objective of the ELF glovebox investigation is to determine the effect of buoyancy on the stability of round, laminar, gas-jet diffusion flames in a co-flow air duct. Comparison tests were conducted in normal gravity to allow isolation and identification of the influence of buoyancy. The results were used to map the lift-off and blow-out stability limits as a function of the fuel and air velocities for the two buoyancy conditions. Approximately 50 tests were conducted during the Space Shuttle mission, using a 50/50 mixture (volume basis) of methane and nitrogen as the fuel. The experimental results verified the hypothesis that substantially greater velocities are required to destabilize the flame in microgravity. The increase in air velocity required to induce lift off in microgravity (compared to normal gravity) was nearly equal to the increase required to induce blow out. Furthermore, the air velocity increase was relatively independent of the fuel flow, except at low fuel flows. At high fuel flows, it was found that the microgravity flames tend to immediately blow out after lift off. This is in agreement with the free-jet theory which suggests that stable lifted flames are not possible for fuels with a Schmidt number of 0.5
TL;DR: In this paper, computer simulations are used to investigate a phenomenon of vorticity enhanced diffusion (VED), a net transport and mixing of a passive scalar across a prescribed vortex flow field driven by a background gradient in the scalar quantity.
Abstract: Computer simulations are used to investigate a phenomenon of vorticity enhanced diffusion (VED), a net transport and mixing of a passive scalar across a prescribed vortex flow field driven by a background gradient in the scalar quantity. The central issue under study here is the increase in scalar flux down the gradient and across the vortex field. The numerical scheme uses cylindrical coordinates centered with the vortex flow which allows an exact advective solution and 1D or 2D diffusion using simple numerical methods. In the results, the ratio of transport across a localized vortex region in the presence of the vortex flow over that expected for diffusion alone is evaluated as a measure of VED. This ratio is seen to increase dramatically while the absolute flux across the vortex decreases slowly as the diffusion coefficient is decreased. Similar results are found and compared for varying diffusion coefficient, {ital D}, or vortex rotation time, {tau}{sub v}, for a constant background gradient in the transported scalar vs an interface in the transported quantity, and for vortex flow fields constant in time vs flow which evolves in time from an initial state and with a Schmidt number of order unity. A simple analysismore » shows that for a small diffusion coefficient, the flux ratio measure of VED scales as the vortex radius over the thickness for mass diffusion in a viscous shear layer within the vortex characterized by (D{tau}{sub v}){sup 1/2}. The phenomenon is linear as investigated here and suggests that a significant enhancement of mixing in fluids may be a relatively simple linear process. Discussion touches on how this vorticity enhanced diffusion may be related to mixing in nonlinear turbulent flows. {copyright} {ital 1999 American Institute of Physics.}« less
01 Jan 1999
TL;DR: In this article, the scalar mixing in isotropic turbulence with Schmidt numbers ranging from 0.04 up to 144 was studied by numerical simulation and it was shown that scalar spectra show a k − 1 range for Sc>1.
Abstract: Scalar mixing in isotropic turbulence with Schmidt numbers ranging from 0.04 up to 144 is studied by numerical simulation. The scalar spectra show a k −1 range for Sc>1. Also for Sc 1. The local fine-scale structure of the velocity field appears to have an effect on the scalar mixing process for all Schmidt numbers.
15 Sep 1999
TL;DR: A Lagrangian stochastic model for the dispersion and deposition of submicron-size particles is formulated and validated, which predicts, in close accord with experiment and the results of direct numerical simulations, that the nondimensional particle deposition velocity K(+) is overpredicted by several orders of magnitude.
Abstract: A Lagrangian stochastic model for the dispersion and deposition of submicron-size particles is formulated and validated. The model satisfies the well-mixed condition, incorporates molecular diffusivity, and accounts for the effects of Reynolds number upon Lagrangian particle statistics. Reynolds number effects are found to be significant in the viscous sublayer and the buffer zone of a turbulent shear flow. The effects are due almost entirely to the change in the Lagrangian integral time scale. Sawford's correction to first-order Lagrangian stochastic models for the effects of Reynolds number is found to be appropriate for inhomogeneous turbulence even when the Taylor–Reynolds number R λ ∼ O(0.1). The model predicts, in close accord with experiment and the results of direct numerical simulations, that the nondimensional particle deposition velocity K + = 0.06Sc −2/3 , where Sc is the Schmidt number. When Reynolds number effects are neglected, K + is overpredicted by several orders of magnitude.
11 Jan 1999