学術雑誌論文

学術雑誌論文

Physical Review Fluids. 2020, 5(6), p. 063901

Conical shear-driven parametric instability of steady flow in precessing spheroids

American Physical Society

英語

2020-06-16

https://doi.org/10.1103/PhysRevFluids.5.063901

Horimoto Y., Katayama A., Goto S. Conical shear-driven parametric instability of steady flow in precessing spheroids. Physical Review Fluids 5, 063901 (2020); https://doi.org/10.1103/PhysRevFluids.5.063901.

We investigate experimentally the instability of steady flow of fluid confined in weakly precessing spheroids. It is known that the conical-shear instability (CSI) proposed by Lin, Marti, and Noir [Phys. Fluids 27, 046601 (2015)] grows in a precessing sphere, and the elliptical and shearing instabilities [Kerswell, Geophys. Astrophys. Fluid Dyn. 72, 107 (1993)] can grow in precessing spheroids. Previous theories predict that when Re≲𝜂−5, where Re is the Reynolds number defined by the spin angular velocity and the equatorial radius of the spheroid and 𝜂 is its ellipticity, CSI dominates the other two instabilities even in a spheroid, and that, in particular, when 𝜂<0.17 the critical Poincaré number (i.e., the critical precession rate) Po(𝑐) is proportional to Re−3/10 for 200⁢𝜂−2≪Re≲𝜂−5. To experimentally verify these predictions, we measure a long time-series of fluid velocity to accurately estimate the power spectrum. Then, we determine Po(𝑐) as a function of Re and show the qualitative change of its scaling depending on 𝜂. Our experimental results perfectly support the theoretical predictions, implying that CSI can grow in precessing spheroids.

Copyright 2020 by the American Physical Society

100044

Conical shear-driven parametric instability of steady flow in precessing spheroids

American Physical Society

英語

2020-06-16

Physical Review Fluids

5

6

063901

https://doi.org/10.1103/PhysRevFluids.5.063901

https://hdl.handle.net/11094/100044