Unsteady detonation with thermodynamic nonequilibrium effect based on the kinetic theory

Abstract

The unsteady detonation is simulated and investigated from the viewpoint of kinetic theory in this paper. The deviations of the velocity distribution function from the equilibrium state are studied in the evolution of detonation. It has been discovered that the characteristics of the deviation around the detonation wave are significantly different from those in the post-wave region. Besides, the kinetic moments of reaction term have been simulated, verified and analyzed in detail. In addition, the reaction manifestation is defined to describe the global effects of kinetic moments due to chemical reactions. It is interesting to find that there are three types of periodic oscillations of the reaction manifestation during the evolution of the unsteady detonation. Via the fast Fourier transform, it can be seen that the reaction manifestation is mainly composed of several signal frequencies. Moreover, the impact of rate constants of two-step reaction scheme on the reaction manifestation is studied, and the influence of chemical heat is investigated as well.

Discrete Boltzmann model with split collision for nonequilibrium reactive flows*

“…To solve the aforementioned issues, one way is to resort to the mesoscopic description that bridges the microscopic molecular and macroscopic continuous models. As a kinetic methodology, the discrete Boltzmann method (DBM) is regarded as a promising tool for mimicking multi-physics flow phenomena [6][7][8][9][10][11][12][13][14][15][16][17][18]. The DBM is a variant version of the standard lattice Boltzmann method (LBM) that has achieved great success in simulating complex reactive or nonreactive flows [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

“…It should be pointed out that the last aforementioned difference is the key reason why the DBM has been developed. The DBM is derived from the nonequilibrium statistical physics and has been successfully applied to investigate compressible reacting flows [7][8][9][10][11][12][13][14][15][16][17][18], multiphase [40][41][42][43], and fluid instabilities [44][45][46][47][48][49][50][51][52], etc. In 2013, the pioneering DBM for combustion was developed by using a hybrid scheme, and the hydrodynamic and thermodynamic nonequilibrium effects were investigated around the detonation wave [7].…”

“…In 2022, the DBM was used to study the quantitative discrepancy between equilibrium and nonequilibrium distribution functions around the detonation wave [17]. In 2023, via the DBM and the fast Fourier transform, the deviations of the velocity distribution function from the equilibrium state have been investigated and the kinetic moments of reaction terms have been discussed in the evolution of unsteady detonation [18].…”