Madja A J, Shefter M
Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA.
Proc Natl Acad Sci U S A. 1998 Jul 7;95(14):7850-3. doi: 10.1073/pnas.95.14.7850.
In contrast to conventional expectations based on the stability of steady shear flows, elementary time-periodic stratified flows that are unstable at arbitrarily large Richardson numbers are presented here. The fundamental instability is a parametric one with twice the period of the basic state. This instability spontaneously generates local shears on buoyancy time scales near a specific angle of inclination that saturates into a localized regime of strong mixing with density overturning. We speculate that such instabilities may contribute significantly to the step-like microstructure often observed in buoyancy measurements in the ocean.
与基于稳定剪切流稳定性的传统预期相反，本文给出了在任意大的理查森数下都不稳定的基本时间周期分层流。基本不稳定性是一种参数不稳定性，其周期是基本状态的两倍。这种不稳定性在接近特定倾斜角度的浮力时间尺度上自发产生局部剪切，进而饱和到一个具有密度反转的强混合局部区域。我们推测，这种不稳定性可能对海洋浮力测量中经常观察到的阶梯状微观结构有显著贡献。
