Non-normal effects in rotating channel flow stability and transition
Complex systems and Biological physics seminar
Wednesday 12 June 2019
to 15:00 at
Sharath K. Jose (Aerospace Engineering Department, IIT Madras)
The rotating channel flow is a plane shear flow system where exponential instabilities can set in at very low values of Reynolds number. The modal critical Reynolds number is a very sensitive function of the roation rate. Therefore a transitioned flow can be readily obtained where the fluctuations can be localised and the mean flow being distinctly asymmetric about the channel centreline. For plane shear flows, how non-normality of the linear stability operator translates to mechanisms responsible for transient growth of perturbation energy and sub-critical transition is well established. The effect of non-normality is traditionally taken into consideration when the base flow is stable to exponentially growing modal instabilities. For this talk, how the linear non-modal stability characteristics vary as a function of rotation, even within a regime where exponential instabilities exist, is discussed. Through results obtained from direct numerical simulations, the nonlinear flow transition will be discussed to augment the linear results. To conclude, using concepts of pseudospectra, we highlight how the sensitivity of the modal critical Reynolds number is also linked to non-normal nature of the non-rotating stability operator.