Author(s): Yarzar Tun, Abdolmajid Mohammadian
Linked Author(s):
Keywords: Shallow water, hydrodynamic instability, pseudospectra, nonmodal analysis
Abstract: A linear stability analysis and nonmodal stability analysis is conducted for an open channel flow to study the conditions under which perturbations growth and develop into large scale lateral motion or �transverse motion�. Linear stability analysis is widely used in the analysis of shallow flows. However, it is well known that linear stability analysis is not reliable when it comes to shear driven flows. Nonmodal stability analysis, on the other hand, gives a more complete picture of instabilities. A hyperbolic tangent velocity profile, which is commonly used to approximate shallow mixing layers, is analyzed. Some nonmodal stability metrics are used as an indication of finite time instability and confirmed by plotting the energy in the perturbations over time. It is shown that some linearly stable cases presented in literature do in fact exhibit transient energy growth, which can be significant enough to generate coherent turbulent structures and may take some time for it to dissipate
Year: 2017