Kinetic Simulation of Unsteady Detonation with Thermodynamic Nonequilibrium Effects
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Kinetic Simulation of Unsteady Detonation with Thermodynamic Nonequilibrium Effects C. Lina and K. H. Luob
UDC 536.46
Published in Fizika Goreniya i Vzryva, Vol. 56, No. 4, pp. 73–82, July–August, 2020. Original article submitted December 26, 2019; revision submitted February 19, 2020; accepted for publication February 19, 2020.
Abstract: Thanks to its mesoscopic kinetic nature, the discrete Boltzmann method has a capability of investigating unsteady detonation with essential hydrodynamic and thermodynamic nonequilibrium effects. In this work, an efficient and precise reactive discrete Boltzmann method is employed to investigate the impact of the amplitude and wave length of the initial perturbation, as well as of the chemical heat on the evolution of unsteady detonation with nonequilibrium effects. It is shown that the initial perturbation amplitude only affects the unsteady detonation in the early period, and the detonation becomes self-similar with minor phase differences later on. For small wave lengths, the pressure increases faster with a higher oscillation frequency in the early period, but decreases soon afterwards. With increasing chemical heat release, the pressure and its oscillations increase, and the nonequilibrium effects become more pronounced, but the oscillatory period decreases. When the wave length or chemical heat release is small enough, there is no transverse wave or cellular pattern, and the two-dimensional unsteady detonation reduces to the one-dimensional case. Keywords: unsteady detonation, thermodynamic nonequilibrium. DOI: 10.1134/S0010508220040073
INTRODUCTION Detonation is a type of a compressible reactive fluid flow induced by a pre-shock wave, after which the chemical heat releases violently [1, 2]. The shock wave coupled with a chemical reaction zone is regarded as a detonation wave propagating forward with a supersonic speed. Detonation has numerous applications in engineering, industry, and safety, such as mining, gas explosion, detonation engine, etc. Due to its great importance, detonation has been studied extensively with experimental [3–5], analytical [6, 7], and numerical methods [8–10] since more than a century ago. With the rapid development of computational science, numerical simulations are indispensable for studying detonaa
Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Zhuhai, 519082 China; [email protected]. b University College London, London WC1E 7JE, United Kingdom; [email protected].
tion [8–10]. At present, however, mimicking the detonation process with high accuracy, efficiency, and robustness remains a great challenge, because detonation involves a broad range of physicochemical phenomena, interacts over various spatial and temporal scales, contains changeable fluid interfaces, where both hydrodynamic and thermodynamic nonequilibrium effects often play essential roles [11–13]. As a central equation in the kinetic theory, the Boltzmann equation has a capability of describing complex fluid flows with abundant nonequilibrium effects. H
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