Non-modal stability of round viscous jets
Non-modal stability of round viscous jets
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DOI：
10.1017/jfm.2012.521
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发表时间：
2013-01
影响因子：
3.7
通讯作者：
S. Boronin;J. Healey;S. Sazhin
中科院分区：
文献类型：
--
作者：
S. Boronin;J. Healey;S. Sazhin
摘要本文用非模态方法研究了圆形粘性流体射流的流体动力稳定性。射流和周围气体都被假定为不可压缩的牛顿流体，并考虑了表面毛细压力的影响。将线性化的Navier-Stokes方程与喷流轴、界面和无穷远处的边界条件相耦合，化为一个求解空间简正模扰动振幅的常微分方程组。用正交化法和牛顿迭代法求解特征值问题，找到了最不稳定的简正模态系统，找到了在给定的控制参数下使系统动能最大的模态线性组合（最优扰动），并对空气射流和液体射流进行了最优扰动的参数研究。对于所考虑的速度分布，它被发现，非模态不稳定机制是显着的非轴对称扰动。在雷诺数为1000时，射流最佳扰动的最大能量比单一模态的最大能量大两个数量级。最大的增长是由流向速度分量获得的。
Abstract Hydrodynamic stability of round viscous fluid jets is considered within the framework of the non-modal approach. Both the jet fluid and surrounding gas are assumed to be incompressible and Newtonian; the effect of surface capillary pressure is taken into account. The linearized Navier–Stokes equations coupled with boundary conditions at the jet axis, interface and infinity are reduced to a system of four ordinary differential equations for the amplitudes of disturbances in the form of spatial normal modes. The eigenvalue problem is solved by using the orthonormalization method with Newton iterations and the system of least stable normal modes is found. Linear combinations of modes (optimal disturbances) leading to the maximum kinetic energy at a specified set of governing parameters are found. Parametric study of optimal disturbances is carried out for both an air jet and a liquid jet in air. For the velocity profiles under consideration, it is found that the non-modal instability mechanism is significant for non-axisymmetric disturbances. The maximum energy of the optimal disturbances to the jets at the Reynolds number of 1000 is found to be two orders of magnitude larger than that of the single mode. The largest growth is gained by the streamwise velocity component.