One-dimensional, unsteady gaseous detonation propagation in a non-homogeneous medium is investigated numerically using the reactive, compressible Navier–Stokes equations with detailed chemistry. The effect of concentration inhomogeneity on the pulsating mode is modeled by a sinusoidal distribution of H2 mole fraction in a H2–O2 mixture. The mixture inhomogeneity, varied by changing the disturbance frequency and amplitude, has significant effects on the pulsating behavior of the detonation due to the interaction of the leading shock with the local gradient. Initially exhibiting a four-period pulsation, the detonation wave entering a non-homogeneous medium can adapt and re-establish into a new propagation mode. For a fixed, large-amplitude sinusoidal disturbance, the period-doubling limit cycle is prone to be destroyed, resulting in a chaotic mode for the propagating detonation front in the non-homogeneous mixture; lowering the disturbance frequency also favors a transition from a periodic pulsation to a chaotic one. When the disturbance amplitude decreases, the propagating detonation can transit quickly to a new pulsating behavior, which tends to be more regular. For a very small amplitude of inhomogeneous variation, it is found that the frequency corresponding to the wavelength close to that of the intrinsic pulsation in the uniform mixture makes the original four-period mode become a double-period mode; for a frequency less than this value, the double-period mode is prone to become more unstable. Consequently, this demonstrates that inhomogeneity could have a positive effect on stabilizing a pulsating detonation.

中文翻译：

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浓度不均匀性对氢氧爆轰脉动不稳定性的影响

使用具有详细化学性质的反应性、可压缩 Navier-Stokes 方程，对非均质介质中的一维不稳定气体爆炸传播进行了数值研究。浓度不均匀性对脉动模式的影响通过 H2-O2 混合物中 H2 摩尔分数的正弦分布建模。由于超前激波与局部梯度的相互作用，通过改变扰动频率和幅度而改变的混合物不均匀性对爆震的脉动行为具有显着影响。最初表现出四周期脉动，进入非均匀介质的爆震波可以适应并重新建立为新的传播模式。对于固定的大振幅正弦扰动，倍周期极限环容易被破坏，导致非均质混合物中传播的爆轰前沿的混沌模式；降低扰动频率也有利于从周期性脉动过渡到混沌脉动。当扰动幅度减小时，传播的爆震可以迅速转变为一种新的脉动行为，这种行为趋于更规律。对于幅度很小的不均匀变化，发现均匀混合物中接近固有脉动波长对应的频率使原来的四周期模变成双周期模；对于小于该值的频率，双周期模式容易变得更加不稳定。因此，这表明不均匀性可能对稳定脉动爆震产生积极影响。