Non-equilibrium effects on flow past a circular cylinder in the slip and early transition regime

Gu, Xiaojun; Barber, Robert W.; John, Benzi; Emerson, David R.

doi:10.1017/jfm.2018.869

Cited by 28 publications

(11 citation statements)

References 73 publications

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“…A number of studies have used DSMC to study subsonic flows through channels or porous materials [19][20][21][22][23][24][25][26][27][28]. Fewer studies have investigated subsonic, external aerodynamic flows around a body [12,[29][30][31]. The current study simulates heated circular cylinders with infinite length at very low Reynolds number values.…”

Section: Gasmentioning

confidence: 99%

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Low-Speed DSMC Simulations of Hotwire Anemometers at High-Altitude Conditions

Roseman

Argrow

2021

Fluids

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Numerical simulations of hotwire anemometers in low-speed, high-altitude conditions have been carried out using the direct simulation Monte Carlo (DSMC) method. Hotwire instruments are commonly used for in-situ turbulence measurements because of their ability to obtain high spatial and temporal resolution data. Fast time responses are achieved by the wires having small diameters (1–5 μm). Hotwire instruments are currently being used to make in-situ measurements of high-altitude turbulence (20–40 km). At these altitudes, hotwires experience Knudsen number values that lie in the transition-regime between slip-flow and free-molecular flow. This article expands the current knowledge of hotwire anemometers by investigating their behavior in the transition-regime. Challenges involved with simulating hotwires at high Knudsen number and low Reynolds number conditions are discussed. The ability of the DSMC method to simulate hotwires from the free-molecular to slip-flow regimes is demonstrated. Dependence of heat transfer on surface accommodation coefficient is explored and discussed. Simulation results of Nusselt number dependence on Reynolds number show good agreement with experimental data. Magnitude discrepancies are attributed to differences between simulation and experimental conditions, while discrepancies in trend are attributed to finite simulation domain size.

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Section: Gasmentioning

confidence: 99%

“…where n f is the gas number density at [12,22,23,30,35,36]. A value of N ppc = 10 was used for results presented in the current study.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Low-Speed DSMC Simulations of Hotwire Anemometers at High-Altitude Conditions

Roseman

Argrow

2021

Fluids

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“…To remedy the deficiency of the R13 equations, the governing equations of the high-order moment quantities m ijk , R ij , ∆ that can be derived from the Boltzmann equation are employed in the present study. They are [28,29]:…”

Section: Extended Thermodynamic Governing Equationsmentioning

confidence: 99%

“…The R13 equations are able to capture non-equilibrium phenomena at a Knudsen number below 0.25. Furthermore, Gu and Emerson [28] extended the method of moments to derive the regularised 26 (R26) moment equations, which demonstrated their potential as an engineering design tool for non-equilibrium flows in the early transition regime [29,30]. The moment method essentially bridges the gap between conventional hydrodynamic models and kinetic models in the early transition regime, where the NSF and the DVM become either inaccurate or inefficient.…”

Section: Introductionmentioning

confidence: 99%

Modelling Thermally Induced Non-Equilibrium Gas Flows by Coupling Kinetic and Extended Thermodynamic Methods

Yang

Emerson

et al. 2019

Entropy

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Thermally induced non-equilibrium gas flows have been simulated in the present study by coupling kinetic and extended thermodynamic methods. Three different types of thermally induced gas flows, including temperature-discontinuity- and temperature-gradient-induced flows and radiometric flow, have been explored in the transition regime. The temperature-discontinuity-induced flow case has shown that as the Knudsen number increases, the regularised 26 (R26) moment equation system will gradually loss its accuracy and validation. A coupling macro- and microscopic approach is employed to overcome these problems. The R26 moment equations are used at the macroscopic level for the bulk flow region, while the kinetic equation associated with the discrete velocity method (DVM) is applied to describe the gas close to the wall at the microscopic level, which yields a hybrid DVM/R26 approach. The numerical results have shown that the hybrid DVM/R26 method can be faithfully used for the thermally induced non-equilibrium flows. The proposed scheme not only improves the accuracy of the results in comparison with the R26 equations, but also extends their capability with a wider range of Knudsen numbers. In addition, the hybrid scheme is able to reduce the computational memory and time cost compared to the DVM.

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“…In the moment method, body fitted grid is employed. The computational domain is 1500 times larger than D and the independence of the results on the spatial grids has been tested in Ref [21], however, in the DVM simulation, traditional Cartesian coordinate is used, which may cause extra error in the simulation. As shown in figure 4, the R26 method is able to capture the temperature feature predicted in the DVM.…”

Section: G =mentioning

confidence: 99%

Comparative study of the discrete velocity and the moment method for rarefied gas flows

Yang

Emerson

et al. 2019

31st International Symposium on Rarefied Gas Dynamics: Rgd31

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In the study of rarefied gas dynamics, the discrete velocity method (DVM) has been widely employed to solve the gas kinetic equations. However, it is usually computationally expensive in dealing with complex geometry and high Mach number flows. In the present work, both classical third-order time implicit DVM and the moment method are employed in finding steady-state solutions of the force-driven Poiseuille flow and flow past a circle cylinder. Their performance, in terms of accuracy, has been compared and analyzed. Choosing the velocity distribution functions (VDFs) obtained from DVM solutions as the benchmark, we reconstruct the expanded VDFs using regularized 13 moment equations (R13) and regularized 26 moment equations (R26) and then compare the accuracy of the expanded VDFs with different order of Hermite polynomial expansions. From the computed velocity profiles and reconstructed VDFs, we have found that the moment method can extend the macroscopic equations into the early transition regime, and the R26 can relatively accurately represent the characteristics of the VDFs in comparison with the gas kinetic model. Conversely, the Navier-Stokes-Fourier (NSF) equations are not able to produce an accurate description of the expanded distribution functions.

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Non-equilibrium effects on flow past a circular cylinder in the slip and early transition regime

Cited by 28 publications

References 73 publications

Low-Speed DSMC Simulations of Hotwire Anemometers at High-Altitude Conditions

Low-Speed DSMC Simulations of Hotwire Anemometers at High-Altitude Conditions

Modelling Thermally Induced Non-Equilibrium Gas Flows by Coupling Kinetic and Extended Thermodynamic Methods

Comparative study of the discrete velocity and the moment method for rarefied gas flows

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