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Rarefaction

About: Rarefaction is a research topic. Over the lifetime, 1852 publications have been published within this topic receiving 26943 citations.


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TL;DR: In this paper, inviscid and viscous flows of a BZT fluid past an airfoil are investigated using accurate thermo-physical models for gases close to saturation conditions and a third-order centred numerical method.
Abstract: A numerical investigation of transonic and low-supersonic flows of dense gases of the Bethe–Zel'dovich–Thompson (BZT) type is presented. BZT gases exhibit, in a range of thermodynamic conditions close to the liquid/vapour coexistence curve, negative values of the fundamental derivative of gasdynamics. This can lead, in the transonic and supersonic regime, to non-classical gasdynamic behaviours, such as rarefaction shock waves, mixed shock/fan waves and shock splitting. In the present work, inviscid and viscous flows of a BZT fluid past an airfoil are investigated using accurate thermo-physical models for gases close to saturation conditions and a third-order centred numerical method. The influence of the upstream kinematic and thermodynamic conditions on the flow patterns and the airfoil aerodynamic performance is analysed, and possible advantages deriving from the use of a non-conventional working fluid are pointed out.

61 citations

Journal ArticleDOI
TL;DR: In this article, the Graetz problem inside the microtube is revisited considering rarefaction effect, viscous dissipation term and axial conduction in the fluid for uniform wall temperature boundary condition in the slip flow regime.

61 citations

Journal ArticleDOI
TL;DR: The flexible asymmetric shock tube (FAST) as mentioned in this paper is a Ludwieg tube-type facility designed and built at Delft University of Technology to measure the velocity of waves propagating in dense vapours of organic fluids, in the so-called non-ideal compressible fluid dynamics (NICFD) regime.
Abstract: This paper describes the commissioning of the flexible asymmetric shock tube (FAST), a novel Ludwieg tube-type facility designed and built at Delft University of Technology, together with the results of preliminary experiments. The FAST is conceived to measure the velocity of waves propagating in dense vapours of organic fluids, in the so-called non-ideal compressible fluid dynamics (NICFD) regime, and can operate at pressures and temperatures as high as 21 bar and 400 ?C, respectively. The set-up is equipped with a special fast-opening valve, separating the high-pressure charge tube from the low-pressure plenum. When the valve is opened, a wave propagates into the charge tube. The wave speed is measured using a time-of-flight technique employing four pressure transducers placed at known distances from each other. The first tests led to the following results: (1) the leakage rate of 5×10?4mbarl s?1 for subatmospheric and 5×10?2mbarl s?1 for a superatmospheric pressure is compatible with the purpose of the conceived experiments, (2) the process start-up time of the valve has been found to be between 2.1 and 9.0 ms, (3) preliminary rarefaction wave experiments in the dense vapour of siloxane D6 (dodecamethylcyclohexasiloxane, an organic fluid) were successfully accomplished up to temperatures of 300?C, and (4) a method for the estimation of the speed of sound from wave propagation experiments is proposed. Results are found to be within 2.1 % of accurate model predictions for various gases. The method is then applied to estimate the speed of sound of D6 in the NICFD regime.

59 citations

Journal ArticleDOI
TL;DR: In this paper, an extended continuum-based approach for analyzing micro-scale gas flows over a wide range of Knudsen number and Mach number was proposed, which implicitly takes care of the complexities in the flow physics in a thermo-physically consistent sense.
Abstract: We test an extended continuum-based approach for analyzing micro-scale gas flows over a wide range of Knudsen number and Mach number. In this approach, additional terms are invoked in the constitutive relations of Navier–Stokes–Fourier equations, which originate from the considerations of phoretic motion as triggered by strong local gradients of density and/or temperature. Such augmented considerations are shown to implicitly take care of the complexities in the flow physics in a thermo-physically consistent sense, so that no special boundary treatment becomes necessary to address phenomenon such as Knudsen paradox. The transition regime gas flows, which are otherwise to be addressed through computationally intensive molecular simulations, become well tractable within the extended quasi-continuum framework without necessitating the use of any fitting parameters. Rigorous comparisons with direct simulation Monte Carlo (DSMC) computations and experimental results support this conjecture for cases of isothermal pressure driven gas flows and high Mach number shock wave flows through rectangular microchannels.

59 citations

Journal ArticleDOI
TL;DR: In this paper, the rarefaction of a free jet expanding into a region of finite background pressure is considered and a simple scattering formulation of the complex physical problem is proposed Comparison of the scattering prediction and previous molecular beam flux measurements by Fenn and Anderson are presented.
Abstract: In this paper the rarefaction of a free jet expanding into a region of finite background pressure is considered It is found that the rarefaction process can be described by a simple rarefaction parameter D(P SP B^1^ / T Here D is the sonic orifice diameter, P8 is the reservoir pressure, PBW is the background pressure and T is the background and reservoir temperatures which are considered to be the same A simple scattering formulation of the complex physical problem is proposed Comparison of the scattering prediction and previous molecular beam flux measurements by Fenn and Anderson are presented A consistent physical description of a plume's approach to the limit of expansion into a perfect vacuum is discussed

58 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20224
2021105
202064
201964
201864
201773