Comparison between Navier-Stokes and DSMC Calculations for Low Reynolds Number Slip Flow Past a Confined Microsphere

Stefanov, Stefan; Barber, Robert W.; Ota, Masahiro; Emerson, David R.

doi:10.1063/1.1941617

Cited by 10 publications

(6 citation statements)

References 3 publications

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“…The data in best agreement with the model are the D p = 7.6 µm, P = 760 Torr data, which fall within the slip-flow regime (0.01 < M/ √ Re < 0.1). These findings join other studies [1,23,[43][44][45][46] in illustrating that C D is not solely a function of Re, but also of metrics that reflect changing flow conditions, such as M and Kn. The increasing deviation of the M > 1.2 empirical C D data from the Carlson-Hoglund model in Figure 4 is attributed to the suppression of flow characteristics in increasingly rarefied conditions.…”

Section: Resultssupporting

confidence: 87%

“…This approximation is provided in Figure 3 and shows reasonable agreement with the subsonic P = 760 Torr results from the present work for M < 0.8. This and other approximations of the standard drag curve [31][32][33][34][35][36][37][38][39][40][41][42] overestimate subsonic C D for the P = 76 Torr condition because they are purely functions of Re and do not account for Kn, where Kn describes the degree of rarefaction by the ratio of the molecular mean free path of the fluid to the diameter of the sphere [1,23,30,[43][44][45][46]. The Kn value for the P = 76 Torr condition was 0.18, corresponding to the transitional-flow regime between slip-flow and free-molecule flow [30].…”

Section: Resultsmentioning

confidence: 99%

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Pressure- and Size-Dependent Aerodynamic Drag Effects on Mach 0.3–2.2 Microspheres for High-Precision Micro-Ballistic Characterization

2022

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The acceleration of microparticles to supersonic velocities is required for microscopic ballistic testing, a method for understanding material characteristics under extreme dynamic conditions, and for projectile gene and drug delivery, a needle-free administration technique. However, precise aerodynamic effects upon supersonic microsphere motion at sub-300 Reynolds numbers have not been quantified. We derive drag coefficients for microspheres traveling in air at subsonic, transonic, and supersonic velocities from the measured trajectories of microspheres launched by laser-induced projectile acceleration. Moreover, the observed drag effects on microspheres in atmospheric (760 Torr) and reduced pressure (76 Torr) are compared with existing empirical data and drag coefficient models. We find that the existing models adequately predict the drag coefficient for subsonic microspheres, while rarefaction effects cause a discrepancy between the model and empirical data in the supersonic regime. These results will improve microsphere flight modeling for high-precision microscopic ballistic testing and projectile gene and drug delivery.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Pressure- and Size-Dependent Aerodynamic Drag Effects on Mach 0.3–2.2 Microspheres for High-Precision Micro-Ballistic Characterization

2022

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“…which is valid for compressible viscous model at small Knudsen numbers (see [25]). The local Mach number has been expressed using nondimensional variables as follows: The square size (equal to 1) compared to examined disturbance length (5000) is small and hardly visible.…”

Section: Resultsmentioning

confidence: 81%

A two-dimensional computational study of gas flow regimes past of square cylinder confined in a long microchannel

Shterev

Stefanov

2017

European Journal of Mechanics - B/Fluids

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In this paper, the transition between steady and unsteady regimes of the two-dimensional gas flow past a moving square cylinder confined between two parallel plates with equal temperatures was investigated for different subsonic and transonic speeds and blockage ratios B=3, 5, 10 and 20 (B is the ratio between microchannel height and square size). The influence of B on the drag coefficient of the square, pressure at stagnation point and transition between steady and unsteady regime were studied. A set of transition curves were obtained for different blockage ratios. The results showed a similar shape of the neutral curves, which shifts to lower Knudsen and Mach numbers when B decrease. A continuum approach based on the Navier-Stokes-Fourier equations was basically applied to all flow regimes. Navier-Stokes-Fourier equations was calculated numerically by using pressure based finite volume algorithm SIMPLE-TS. For the initial transition velocity slip regime, the results were compared to data obtained by using the particle Direct Simulation Monte Carlo (DSMC) method.

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“…A Hard Sphere (HS) model and the No Time Counter (NTC) scheme suggested by Bird [17] are implemented in the collision algorithm. A slight modification is introduced in the calculation of the maximum number of collisions N C in each cell [20], which is calculated…”

Section: Fig 2: Configuration and Geometric Parametersmentioning

confidence: 99%

Analysis of flow induced by temperature fields in ratchet-like microchannels by Direct Simulation Monte Carlo

Chen

Stefanov

Baldas

et al. 2016

International Journal of Heat and Mass Transfer

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This paper presents a numerical analysis of a novel configuration of Knudsen pump for rarefied gas flow. The pumping element consists of two facing isothermal ratchet surfaces at different temperatures. The asymmetric saw-tooth-like surfaces in optimal geometrical conditions can create temperature inequalities in the near wall region and finally engender a macroscopic flow. The rarefied gas flow is numerically investigated by Direct Simulation Monte Carlo (DSMC) in the slip and transition regimes. A parametric study reveals the effects of several crucial parameters including temperature difference, Knudsen number, accommodation coefficients as well as main geometrical parameters. In particular, the results indicate that the mass flow rate reaches a maximum value for a Knudsen number around 0.1 and becomes negative for a Knudsen number close to unity.

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Comparison between Navier-Stokes and DSMC Calculations for Low Reynolds Number Slip Flow Past a Confined Microsphere

Cited by 10 publications

References 3 publications

Pressure- and Size-Dependent Aerodynamic Drag Effects on Mach 0.3–2.2 Microspheres for High-Precision Micro-Ballistic Characterization

Pressure- and Size-Dependent Aerodynamic Drag Effects on Mach 0.3–2.2 Microspheres for High-Precision Micro-Ballistic Characterization

A two-dimensional computational study of gas flow regimes past of square cylinder confined in a long microchannel

Analysis of flow induced by temperature fields in ratchet-like microchannels by Direct Simulation Monte Carlo

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