Study of rarefied gas flows in backward facing micro-step using Direct Simulation Monte Carlo

Gavasane, Abhimanyu; Agrawal, Amit; Bhandarkar, Upendra

doi:10.1016/j.vacuum.2018.06.014

Cited by 25 publications

(7 citation statements)

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“…Reviewing existing studies on rarefied gas flows over micro-steps (Beskok 2001;Baysal et al 2004;Xue et al 2005;Hsieh et al 2010;Bao & Lin 2011;Darbandi & Roohi 2011;Mahdavi et al 2014;Mahdavi & Roohi 2015;Gavasane et al 2018), the current work presents several new findings that are of fundamental and practical significance. In contrast to the common view, it is first demonstrated that step detachment may occur at free-molecular conditions, identified by a unique velocity profile.…”

Section: Resultsmentioning

confidence: 96%

“…Roohi, Mahdavi and co-workers (Darbandi & Roohi 2011;Mahdavi et al 2014;Mahdavi & Roohi 2015) conducted numerical simulations to analyse the effects of step temperature and gas heat transfer on the flow field. More recently, Gavasane, Agrawal & Bhandarkar (2018) demonstrated the occurrence of the Knudsen paradox in a micro-step channel geometry. The counterpart three-dimensional problem was earlier considered by Hsieh, Hong & Pan (2010).…”

Section: A22-2mentioning

confidence: 99%

“…It is in this limit where the analytic solution becomes of particular value to study the free-molecular flow field, as described below. Based on previous DSMC investigations (Xue et al 2005;Darbandi & Roohi 2011;Mahdavi et al 2014;Mahdavi & Roohi 2015;Gavasane et al 2018), it is expected that no flow detachment (in the form of step separation and recirculation) occurs at free-molecular conditions. This is supported by the results in figure 6, showing fully attached streamline profiles at the step in set-ups with high density and temperature drops.…”

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confidence: 99%

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Free-molecular and near-free-molecular gas flows over backward facing steps

Manela

Gibelli

2020

J. Fluid Mech.

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Section: Resultsmentioning

confidence: 96%

Section: A22-2mentioning

confidence: 99%

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confidence: 99%

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Free-molecular and near-free-molecular gas flows over backward facing steps

Manela

Gibelli

2020

J. Fluid Mech.

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“…This Knudsen number limiting the vortex formation was reduced to 0.82 in the work of Ahangar et al 1 and 0.662 in Ref. 10. Therefore, there is a Knud-sen number limitation of vortex formation and it may be a function of inlet flow conditions; however, the relationship between the specific Knudsen number of vortex formation limitation and the inlet flow condition is not fully understood.…”

Section: E Failure Of Vortex Loop Formationmentioning

confidence: 96%

Numerical investigation of rarefied vortex loop formation due to shock wave diffraction with the use of rorticity

2021

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When compressed gas is ejected from a nozzle into a low-pressure environment, the shock wave diffracts around the nozzle lip and a vortex loop will form. The phenomenon has been widely investigated in the continuum flow regime, but how the shock diffraction and vortex behave under rarefied flow conditions has not received as much attention. It is necessary to understand this transient flow in rarefied environments to improve thrust vector control and avoid potential contamination and erosion of spacecraft surfaces. This work provides numerical results of the vortex loop formation caused by shock wave diffraction around a 90 • corner using the direct simulation Monte Carlo method and the compressible Navier-Stokes equations with the appropriate Maxwell velocity slip and the von Smoluchowski temperature jump boundary conditions. The Mach number and rarefaction effects on the formation and evolution of the vortex loop are discussed. A study of the transient structures of vortex loops has been performed using the rorticity concept. A relationship of mutual transformation between the rorticity and shear vectors has been discovered, demonstrating that the application of this concept is useful to understand vortex flow phenomena.

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“…Gavasane et al. 33 studied argon flow through a micro-BFS for different Kn and pressure ratios. From the above discussion, it can be observed that most of the studies either considered monoatomic argon or diatomic nitrogen as the fluid in their investigations.…”

Section: Introductionmentioning

confidence: 99%

DSMC simulation of rarefied gas flow over a 2D backward-facing step in the transitional flow regime: Effect of Mach number and wall temperature

Nabapure

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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Rarefied gas flow over a backward-facing step (BFS) is often encountered in separating flows prevalent in aerodynamic flows, engine flows, condensers, space vehicles, heat transfer systems, and microflows. Direct Simulation Monte Carlo (DSMC) is a powerful tool to investigate such flows. The purpose of this research is to assess the impact of Mach number and wall temperature on the flow and surface properties in the transitional flow regime. The Mach numbers considered are 5, 10, 25, 30, and the ratio of the temperature of the wall to that of freestream considered are 1, 2, 4, 8. The Reynolds number for the cases studied is 8.6, 17.2, 43, and 51.7, respectively. Typically the flow properties near the wall are found to increase with both Mach number and wall temperature owing to compressibility and viscous dissipation effects. The variation in flow properties is more sensitive to Mach number than the wall temperature. The surface properties are found to decrease with Mach number and increase with wall temperature. Moreover, in the wake of the step, the vortex’s recirculation length is reasonably independent of both free stream Mach number and wall temperature, whereas it decreases with Knudsen number.

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Study of rarefied gas flows in backward facing micro-step using Direct Simulation Monte Carlo

Cited by 25 publications

References 50 publications

Free-molecular and near-free-molecular gas flows over backward facing steps

Free-molecular and near-free-molecular gas flows over backward facing steps

Numerical investigation of rarefied vortex loop formation due to shock wave diffraction with the use of rorticity

DSMC simulation of rarefied gas flow over a 2D backward-facing step in the transitional flow regime: Effect of Mach number and wall temperature

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