Experiments on free decay of quasi-two-dimensional turbulent flows

Danilov, Sergey; Dolzhanskii, F. V.; Dovzhenko, V. A.; Krymov, V. A.

doi:10.1103/physreve.65.036316

Cited by 25 publications

(10 citation statements)

References 21 publications

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“…The measured flow damping rates are often compared with those derived from a quasi-2D model [11,12], which assumes no vertical motions within the layer. In thin layers, the agreement is usually within a factor of 2 [9,13]. However, in some experiments a much better agreement with the quasi-2D model was observed [14].…”

mentioning

confidence: 84%

Turbulence Decay Rate as a Measure of Flow Dimensionality

2010

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The dimensionality of turbulence in fluid layers determines their properties. We study electromagnetically driven flows in finite-depth fluid layers and show that eddy viscosity, which appears as a result of three-dimensional motions, leads to increased bottom damping. The anomaly coefficient, which characterizes the deviation of damping from the one derived using a quasi-two-dimensional model, can be used as a measure of the flow dimensionality. Experiments in turbulent layers show that when the anomaly coefficient becomes high, the turbulent inverse energy cascade is suppressed. In the opposite limit turbulence can self-organize into a coherent flow.

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confidence: 84%

Turbulence Decay Rate as a Measure of Flow Dimensionality

2010

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“…In a thin layer system bottom friction is an important factor that prevents the flow from being purely 2D. Bottom friction as well as friction due to ordinary viscosity causes the total energy of the flow to decay ͑e.g., Danilov et al 17 ͒. It is important therefore to maintain a rate of energy decrease due to bottom friction that is somewhat less than that due to ordinary viscosity.…”

Section: Experimental Techniquementioning

confidence: 99%

Formation of vortex dipoles

Afanasyev

2006

Physics of Fluids

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Evolution of a two-dimensional flow induced by a jet ejected from a nozzle of finite size is studied experimentally. Vortex dipole forms at the front of the developing flow while a trailing jet establishes behind the dipole. The dynamics of the flow is discussed on the basis of detailed measurements of vorticity and velocity fields which are obtained using particle image velocimetry. It is found that dipoles do not separate ͑pinch-off͒ from the trailing jet for values of the stroke ratio up to 15, which fact can be contrasted with the behavior of vortex rings reported previously by other authors. A characteristic time scale that is defined differently from the formation time of vortex rings can be introduced. This time scale ͑startup time͒ indicates the moment when the dipole starts translating after an initial period when it mainly grows absorbing the jet from the nozzle. A simple model that considers the competing effects of expansion and translation is developed to obtain an estimate of the dimensionless startup time. The dynamics of a dipole after the formation is characterized by a reduced flux of vorticity from the jet. The dipole moves forward with constant speed such that a value of the ratio of the speed of propagation of the dipole to the mean velocity of the jet is found to be 0.5. A universality of this ratio is explained in the framework of a model based on conservation of mass and momentum for the moving dipole.

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“…A similar electromagnetic technique has been used extensively in experiments on two-dimensional turbulence in thin layers of electrolytic fluid (e.g. Hansen et al, 1998;Danilov et al, 2002). 82 Y. AFANASYEV A typical value of the momentum flux delivered by each magnet to the fluid was I ¼ 0.15 cm 4 s À2 .…”

Section: Laboratory Apparatus and Techniquementioning

confidence: 99%

Spontaneous Emission of Gravity Waves by Interacting Vortex Dipoles in a Stratified Fluid: Laboratory Experiments

Afanasyev

2003

Geophysical & Astrophysical Fluid Dynamics

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Results from a new series of experiments on the geophysically important issue of spontaneous emission of internal gravity waves during unsteady interactions of vortical structures are presented. Vortex dipoles are a common element of a quasi-two-dimensional turbulent flow. Vortex dipoles perform translational motion and can collide with other vortices. During collision events the flow is unsteady and unbalanced and a further adjustment process associated with these events can therefore result in the spontaneous emission of gravity waves. Our laboratory experiments demonstrate that gravity waves are emitted when two translating vortex dipoles interact (collide) in a layered fluid, in accord with the current theoretical results. The emission was evident both in a two-layer system and in a fluid with a linear distribution of density with depth. The waves were generated during the period of deceleration of the secondary dipoles which constitute a vortex quadrupole emerging immediately after the collision of the primary dipoles.

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Experiments on free decay of quasi-two-dimensional turbulent flows

Cited by 25 publications

References 21 publications

Turbulence Decay Rate as a Measure of Flow Dimensionality

Turbulence Decay Rate as a Measure of Flow Dimensionality

Formation of vortex dipoles

Spontaneous Emission of Gravity Waves by Interacting Vortex Dipoles in a Stratified Fluid: Laboratory Experiments

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