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09:58
Investigating the Three-dimensional Flow Separation Induced by a Model Vocal Fold Polyp
Published on: February 3, 2014
Shear flow and Kelvin-Helmholtz instability in superfluids
R Blaauwgeers1, V B Eltsov, G Eska
1Low Temperature Laboratory, Helsinki University of Technology, P.O. Box 2200, Finland.
Physical Review Letters
|October 9, 2002
Summary
Researchers observed the first instabilities in shear flow between two superfluids. This superfluid 3He study reveals how vortex dynamics at the interface lead to flow instabilities, aligning with modified Kelvin-Helmholtz theory.
Area of Science:
- Condensed Matter Physics
- Quantum Fluids
- Superfluid Hydrodynamics
Background:
- Superfluidity in Helium-3 (3He) exhibits distinct A and B phases with unique quantum properties.
- Shear flow instabilities are crucial phenomena in fluid dynamics, but their study in superfluids is complex.
- Understanding interfacial dynamics is key to characterizing the behavior of multi-phase quantum fluids.
Purpose of the Study:
- To experimentally realize and investigate instabilities in the shear flow between superfluid 3He-A and 3He-B phases.
- To explore the role of quantized vorticity and interfacial modes in driving these instabilities.
- To compare experimental observations with theoretical models, specifically Kelvin-Helmholtz theory.
Main Methods:
- Utilizing a magnetically stabilized interface between superfluid 3He-A and 3He-B.
- Creating a state of discontinuous tangential velocities via uniform rotation.
- Measuring the properties of the flow instability as interfacial modes are excited.
Main Results:
- The shear flow state with discontinuous velocities was found to be stable and nondissipative up to high relative velocities.
- An instability was observed when an interfacial mode was excited, leading to vortex crossings.
- The measured characteristics of the instability closely match predictions from Kelvin-Helmholtz theory adapted for two-fluid hydrodynamics.
Conclusions:
- This study provides the first experimental realization of shear flow instabilities in a superfluid system.
- The findings demonstrate the critical role of quantized vortices and interfacial phenomena in superfluid hydrodynamics.
- The results validate the applicability of modified Kelvin-Helmholtz theory to understand instabilities in two-fluid superfluids.
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