激波与气柱相互作用是Richtmyer-Meshkov不稳定性研究的经典案例.单次激波与二维气柱相互作用已得到广泛关注,但是反射激波再次冲击气柱(尤其是三维气柱)的研究较少,相关演化规律和机理尚不清楚.反射激波再次冲击演化中的气柱界面会产...激波与气柱相互作用是Richtmyer-Meshkov不稳定性研究的经典案例.单次激波与二维气柱相互作用已得到广泛关注,但是反射激波再次冲击气柱(尤其是三维气柱)的研究较少,相关演化规律和机理尚不清楚.反射激波再次冲击演化中的气柱界面会产生新的斜压涡量,影响涡量的输运和分布,从而影响界面的演化.本文采用自主开发的HOWD(high-order WENO and double-flux methods)程序,研究了马赫数为1.29的平面激波冲击N_(2)气柱(气柱外为SF_(6))的演化过程,并考察了反射激波对二维和三维凹气柱界面演化的影响规律.在数值模拟中,选取了不同的反射距离(定义为气柱和反射边界的距离),得到了二维和三维凹气柱在反射激波冲击前后的完整演化图像,提取了气柱上特征点位置随时间变化的定量数据,重点分析了不同演化阶段气柱几何特征及斜压涡量分布的变化趋势.研究表明,反射距离决定着反射激波作用气柱时的激波形状和气柱形态,从而影响斜压涡量的生成和分布,进而改变气柱的不稳定性演化过程.对于三维气柱,不同高度截面上的斜压涡量分布不同,从而诱导出复杂的三维演化结构.展开更多
The interaction of a planar shock with SF_(6)/Ar/He dual interfaces(SF_(6)/Ar interface is sinusoidal and Ar/He interface is unperturbed)is numerically studied with a compressible multi-component flow solver that is c...The interaction of a planar shock with SF_(6)/Ar/He dual interfaces(SF_(6)/Ar interface is sinusoidal and Ar/He interface is unperturbed)is numerically studied with a compressible multi-component flow solver that is capable of simultaneously capturing discontinuities and resolving small-scale smooth structures.Six cases with different interface distances and incident shock strengths are considered.For all cases,after the shock impact,the amplitude of the first interface reduces gradually to zero(i.e.,phase inversion)and then increases continuously in the negative direction.The rarefaction wave(RW2)reflected from the second interface promotes or suppresses the development of the first interface depending on the interface distance(D).Specifically,if D is small,RW2 arrives at the first interface at a time before phase inversion,and thus promotes the instability growth at the first interface.If D is large,RW2 encounters the first interface at a time after phase inversion,and thus suppresses the instability growth.A theoretical model for the critical distance,under which the first interface just completes phase inversion at the arrival time of RW2,is developed.With this model,one can regulate the instability growth at the first interface by giving a desired D.The development of the second interface belongs to non-standard Richtmyer-Meshkov instability,which depends heavily on the phase of the rippled transmitted shock.It is found that the model of Ishizaki(Phys.Rev.E 53,R5592,1996)fails to predict the perturbation growth of the second interface for cases where the transmitted shock is at phase 2 due to the ignorance of baroclinic vorticity.A new model considering the combined effects of baroclinic vorticity,velocity perturbation,and pressure disturbance is proposed,which gives a reasonable prediction of perturbation growth at the second interface.展开更多
文摘激波与气柱相互作用是Richtmyer-Meshkov不稳定性研究的经典案例.单次激波与二维气柱相互作用已得到广泛关注,但是反射激波再次冲击气柱(尤其是三维气柱)的研究较少,相关演化规律和机理尚不清楚.反射激波再次冲击演化中的气柱界面会产生新的斜压涡量,影响涡量的输运和分布,从而影响界面的演化.本文采用自主开发的HOWD(high-order WENO and double-flux methods)程序,研究了马赫数为1.29的平面激波冲击N_(2)气柱(气柱外为SF_(6))的演化过程,并考察了反射激波对二维和三维凹气柱界面演化的影响规律.在数值模拟中,选取了不同的反射距离(定义为气柱和反射边界的距离),得到了二维和三维凹气柱在反射激波冲击前后的完整演化图像,提取了气柱上特征点位置随时间变化的定量数据,重点分析了不同演化阶段气柱几何特征及斜压涡量分布的变化趋势.研究表明,反射距离决定着反射激波作用气柱时的激波形状和气柱形态,从而影响斜压涡量的生成和分布,进而改变气柱的不稳定性演化过程.对于三维气柱,不同高度截面上的斜压涡量分布不同,从而诱导出复杂的三维演化结构.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12122213,12072341,and 91952205).
文摘The interaction of a planar shock with SF_(6)/Ar/He dual interfaces(SF_(6)/Ar interface is sinusoidal and Ar/He interface is unperturbed)is numerically studied with a compressible multi-component flow solver that is capable of simultaneously capturing discontinuities and resolving small-scale smooth structures.Six cases with different interface distances and incident shock strengths are considered.For all cases,after the shock impact,the amplitude of the first interface reduces gradually to zero(i.e.,phase inversion)and then increases continuously in the negative direction.The rarefaction wave(RW2)reflected from the second interface promotes or suppresses the development of the first interface depending on the interface distance(D).Specifically,if D is small,RW2 arrives at the first interface at a time before phase inversion,and thus promotes the instability growth at the first interface.If D is large,RW2 encounters the first interface at a time after phase inversion,and thus suppresses the instability growth.A theoretical model for the critical distance,under which the first interface just completes phase inversion at the arrival time of RW2,is developed.With this model,one can regulate the instability growth at the first interface by giving a desired D.The development of the second interface belongs to non-standard Richtmyer-Meshkov instability,which depends heavily on the phase of the rippled transmitted shock.It is found that the model of Ishizaki(Phys.Rev.E 53,R5592,1996)fails to predict the perturbation growth of the second interface for cases where the transmitted shock is at phase 2 due to the ignorance of baroclinic vorticity.A new model considering the combined effects of baroclinic vorticity,velocity perturbation,and pressure disturbance is proposed,which gives a reasonable prediction of perturbation growth at the second interface.
