Turbulence Simulation on Zonal Flow Formations in the Presence of Parallel Flows

Notions of linear and nonlinear hydrodynamic (in)stability are explained and criteria of instability of plane-parallel flows are presented. Instabilities of jets are investigated by direct pseudospectral collocation method in various flow configurations, starting from the classical barotropic and baroclinic instabilities. Characteristic features of instabilities are displayed, as well as typical patterns of their nonlinear saturation. It is shown that in the Phillips model of Chapter 5, new ageostrophic Rossby–Kelvin and shear instabilities appear at finite Rossby numbers. These instabilities are interpreted in terms of resonances among waves counter-propagating in the flow. It is demonstrated that the classical inertial instability is a specific case of ageostrophic baroclinic instability. At the equator it appears also in the barotropic configuration, and is related to resonances of Yanai waves. The nature of the inertial instability in terms of trapped modes is established. A variety of instabilities of density fronts is displayed.

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Planetary, Inertia‐Gravity and Kelvin waves on the f ‐plane and β ‐plane in the presence of a uniform zonal flow

Quarterly Journal of the Royal Meteorological Society ◽

10.1002/qj.4107 ◽

2021 ◽

Author(s):

Yair De‐Leon ◽

Itzhak Fouxon ◽

Chaim I. Garfinkel ◽

Nathan Paldor

Keyword(s):

Zonal Flow ◽

Kelvin Waves

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Low-cost Solutions for Velocimetry in Rotating and Opaque Fluid Experiments using Ultrasonic Time of Flight

Experimental Techniques ◽

10.1007/s40799-021-00469-x ◽

2021 ◽

Author(s):

Fabian Burmann ◽

Jerome Noir ◽

Stefan Beetschen ◽

Andrew Jackson

Keyword(s):

Acoustic Waves ◽

Flow Measurement ◽

Low Cost ◽

Time Of Flight ◽

Zonal Flow ◽

Gravitational Acceleration ◽

Complex Flow ◽

Ultrasonic Time ◽

Theoretical Predictions ◽

Complex Flow Structure

AbstractMany common techniques for flow measurement, such as Particle Image Velocimetry (PIV) or Ultrasonic Doppler Velocimetry (UDV), rely on the presence of reflectors in the fluid. These methods fail to operate when e.g centrifugal or gravitational acceleration leads to a rarefaction of scatterers in the fluid, as for instance in rapidly rotating experiments. In this article we present two low-cost implementations for flow measurement based on the transit time (or Time of Flight) of acoustic waves, that do not require the presence of scatterers in the fluid. We compare our two implementations against UDV in a well controlled experiment with a simple oscillating flow and show we can achieve measurements in the sub-centimeter per second velocity range with an accuracy of $\sim 5-10\%$ ∼ 5 − 10 % . We also perform measurements in a rotating experiment with a complex flow structure from which we extract the mean zonal flow, which is in good agreement with theoretical predictions.

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