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Periodic flow instabilities in the wake of an ion
Author(s) -
Careri Giorgio
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560220823
Subject(s) - wake , vortex ring , harmonics , ion , critical ionization velocity , physics , reynolds number , vortex , atomic physics , vortex shedding , mechanics , chemistry , condensed matter physics , turbulence , quantum mechanics , voltage
Sudden periodical discontinuities in ionic mobilities, first observed in the 1960s in liquid helium II, are suggested to be due to the excitation of the shedding mode harmonics of the vortex ring formed in the wake of the ion. Thus, this phenomenon would parallel the first monoperiodical regime displayed by other flow systems, where the presence of these harmonics has been detected recently in the velocity spectrum. Since the shedding Reynolds number is found to retain its validity in a low‐polarizability medium such as liquid helium, the critical velocities for the onset of these instabilities have been derived in a temperature range where dimensional analysis can be applied. Predicted critical velocities are in good agreement with the experimental ones, both for positive and negative ions, postulating the existence of a vortex ring in the roton gas of the ion wake. The shedding mode frequency of this vortex ring is evaluated, and experiments are suggested to test its presence. The critical velocity for the formation of a superfluid vortex ring by an ion has been identified, in good agreement with values extrapolated from larger size objects.