The Origin of Turbulence in Near-Wall Flows

Бойко, А. В.; Grek, G. R.; Dovgal, A. V.; Козлов, В. В.

doi:10.1007/978-3-662-04765-1

Cited by 118 publications

(46 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In the classical linear theory of stability of quasi-parallel shear flows, this is explained by the formation in the zone of detachment of the profiles of average velocity with the inflection point, which are more unstable with respect to oscillations of small amplitudes than the local velocity distributions in the attached boundary layer (see the monograph [13] and original works, [14][15][16]). Theoretical conclusions are consistent with the results of experimental studies and direct numerical simulation of flow in local detachment areas, including behind two-dimensional elements of unevenness in a streamlined surface; literary references to numerous publications on this subject are given in [17].…”

Section: Introductionsupporting

confidence: 77%

Generation of localized disturbances by surface vibrations behind the ledge in the laminar flow

Pavlenko

Катасонов

Козлов

et al. 2017

AIP Conference Proceedings

View full text Add to dashboard Cite

Generation of Localized Disturbances by Surface VibrationsBehind the Ledge in the Laminar Flow Abstract. The occurrence and development of hydrodynamic perturbations generated by low-frequency vibrations of a local section of a streamlined surface in a separated flow behind a rectangular ledge on a flat plate are investigated in the wind tunnel. The results were obtained by the hot-wire anemometry method at a low subsonic flow velocity. It is established that vibrations of the wall generate perturbations of the separation zone, which are streaky structures, and accompanying wave packets of oscillations. The separation of the laminar boundary layer promotes the growth of wave packets with subsequent turbulence of the wall flow.

show abstract

Section: Introductionsupporting

confidence: 77%

Generation of localized disturbances by surface vibrations behind the ledge in the laminar flow

Pavlenko

Катасонов

Козлов

et al. 2017

AIP Conference Proceedings

View full text Add to dashboard Cite

show abstract

“…Additionally, they observed reduction of the LSB size from both upstream and downstream directions. Similarly to and Boiko et al (2002), they suggested a feedback loop process to explain the bubble size reduction due to controlled disturbances. More specifically, a disturbance input alters the flow in the aft part of the bubble, resulting in a global change of pressure gradient due to viscous-inviscid interactions.…”

Section: Introductionmentioning

confidence: 85%

Response of a laminar separation bubble to impulsive forcing

2017

View full text Add to dashboard Cite

The spatial and temporal response characteristics of a laminar separation bubble to impulsive forcing are investigated by means of time-resolved particle image velocimetry and linear stability theory. A two-dimensional impulsive disturbance is introduced with an AC dielectric barrier discharge plasma actuator, exciting pertinent instability modes and ensuring flow development under environmental disturbances. Phase-averaged velocity measurements are employed to analyse the effect of imposed disturbances at different amplitudes on the laminar separation bubble. The impulsive disturbance develops into a wave packet that causes rapid shrinkage of the bubble in both upstream and downstream directions. This is followed by bubble bursting, during which the bubble elongates significantly, while vortex shedding in the aft part ceases. Duration of recovery of the bubble to its unforced state is independent of the forcing amplitude. Quasi-steady linear stability analysis is performed at each individual phase, demonstrating reduction of growth rate and frequency of the most unstable modes with increasing forcing amplitude. Throughout the recovery, amplification rates are directly proportional to the shape factor. This indicates that bursting and flapping mechanisms are driven by altered stability characteristics due to variations in incoming disturbances. The emerging wave packet is characterised in terms of frequency, convective speed and growth rate, with remarkable agreement between linear stability theory predictions and measurements. The wave packet assumes a frequency close to the natural shedding frequency, while its convective speed remains invariant for all forcing amplitudes. The stability of the flow changes only when disturbances interact with the shear layer breakdown and reattachment processes, supporting the notion of a closed feedback loop. The results of this study shed light on the response of laminar separation bubbles to impulsive forcing, providing insight into the attendant changes of flow dynamics and the underlying stability mechanisms.

show abstract

“…The disturbance length (200 ms) is equal to the length of pulse, which moves the membrane upward. This structure is corresponding to the longitudinal localized streaky structures, or so-called "puff" structures, which are in more detail investigated at [3][4][5][6][7][8][9][10][11]. Going downstream, the flow pulsations of this structure (u min and u max ) become weaker.…”

Section: Resultsmentioning

confidence: 99%

“…This method makes it possible detailed investigations of characteristics for artificially introduced perturbations with saving of phase information, to trace the dynamics of the development of a concrete perturbation at all its stages. In addition to the widely used suction-injection technique [4,5], another method is also used where the boundary layer disturbances are generated by vibrations of a local surface area. Experimental investigation of the origin and development of disturbances, generated by vibration of three-dimensional surface in the Blasius boundary layer is shown in [6] and for the straight wing boundary layer in [7].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of localized disturbances in the straight wing boundary layer, generated by finite surface vibrations

Козлов

Катасонов

Pavlenko

2017

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. Downstream development of artificial disturbances were investigated experimentally using hot-wire constant temperature anemometry. It is shown that vibrations with high-amplitude of a three-dimensional surface lead to formation of two types of perturbations in the straight wing boundary layer: streamwise oriented localized structures and wave packets. The amplitude of streamwise structure is decay downstream. The wave packets amplitude grows in adverse pressure gradient area. The flow separation is exponentially intensified of the wave packet amplitude.

show abstract

The Origin of Turbulence in Near-Wall Flows

Cited by 118 publications

References 0 publications

Generation of localized disturbances by surface vibrations behind the ledge in the laminar flow

Generation of localized disturbances by surface vibrations behind the ledge in the laminar flow

Response of a laminar separation bubble to impulsive forcing

Experimental investigation of localized disturbances in the straight wing boundary layer, generated by finite surface vibrations

Contact Info

Product

Resources

About