Impulse response of linear disturbances in a skewed Stokes layer

Thomas, Christian and Pretty, Alexander 2025. Impulse response of linear disturbances in a skewed Stokes layer. Physics of Fluids 37 (1) , 014107. 10.1063/5.0249527

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Abstract

The spatiotemporal development of impulsively excited two-dimensional linear disturbances in acceleration-skewed and velocity-skewed Stokes layers is investigated using numerical simulations of the linearized Navier–Stokes equations. This study focuses on the long-term behavior of linearly unstable disturbances within these skewed flows. The onset of linear instability in the symmetric Stokes layer is known to coincide with absolute instability, with disturbances forming family tree structures, characterized by multiple wavepackets spread across the spatiotemporal plane, coupled with pointwise subharmonic temporal growth [Ramage et al., “Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics,” Phys. Rev. Fluids 5, 103901 (2020)]. However, the introduction of acceleration and velocity skewness disrupts the formation of the family tree structure. Instead, the onset of linearly unstable behavior is matched to convective instability, with disturbances predominantly propagating in the direction of the maximum acceleration or maximum velocity. As the Reynolds number increases, absolute instability emerges, albeit with pointwise temporal growth less than the growth obtained by the disturbance maximum.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Mathematics
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2025-01-06
Publisher:	American Institute of Physics
ISSN:	1070-6631
Date of First Compliant Deposit:	20 January 2025
Date of Acceptance:	12 December 2024
Last Modified:	20 Jan 2025 10:30
URI:	https://orca.cardiff.ac.uk/id/eprint/175398

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