Fast-response underwater TSP investigation of subcritical instabilities of a cylinder in crossflow

Capone, Alessandro; Klein, Christian; Felice, Fabio Di; Beifuß, Uwe; Miozzi, Massimo

doi:10.1007/s00348-015-2065-9

Cited by 17 publications

(21 citation statements)

References 42 publications

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“…For the 2D/3D flows, the increase/decrease in the variation range with increasing Re is mainly induced by the increase/decrease in strength of the separating shear layer and hence the cross-flow roll-up of the separating shear layer with increasing Re. While the present study focuses primarily on the early 3D flow states up to Re = 1000, time histories of the instantaneous separation angle at a much higher Re of 7.4×10 4 are available from the experimental study by Capone et al (2015), which enables a similar analysis at this much higher Re. Capone et al (2015) plotted the time histories of the instantaneous separation angle at Re = 7.4×10 4 at two spanwise locations over approximately 45 vortex shedding cycles.…”

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confidence: 99%

“…While the present study focuses primarily on the early 3D flow states up to Re = 1000, time histories of the instantaneous separation angle at a much higher Re of 7.4×10 4 are available from the experimental study by Capone et al (2015), which enables a similar analysis at this much higher Re. Capone et al (2015) plotted the time histories of the instantaneous separation angle at Re = 7.4×10 4 at two spanwise locations over approximately 45 vortex shedding cycles. The averages of the maxima and minima of θs for the first time history are 78.1° and 75.0°, respectively, while those for the second time history are 78.2° and 75.1°, respectively, which suggest that the variation range of the instantaneous separation angle remains small (of approximately 3.1°) at Re = 7.4×10 4 .…”

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confidence: 99%

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Separation angle for flow past a circular cylinder in the subcritical regime

Jiang

2020

Physics of Fluids

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Instantaneous and time-averaged flow separation locations for the canonical case of flow past a circular cylinder are investigated through direct numerical simulations. It is found that the instantaneous movement of the upper/lower separation point on the cylinder surface is governed by a dynamic balance between the upper/lower separating shear layer and a shear layer generated at the back of the cylinder due to wake recirculation. It is also found that flow three-dimensionality contributes to an upstream movement of the time-averaged separation point through the effect of the separating shear layer. For the three-dimensional flow, the disordered mode B flow structures developed in the separating shear layer (which is directly responsible for the flow three-dimensionality) would result in turbulent energy dissipation and therefore the separating shear layer is less rolled-up in the cross-flow direction, which weakens the effect of the separating shear layer in pushing the separation point downstream. The time-averaged separation angle versus Reynolds number (s Re  −) relationship is not monotonic over the three-dimensional wake transition regimes of Re = 190-270, since there is a transition sequence of different wake flow patterns with different levels of flow three-dimensionality. For Re ≥ 270, on the physical basis that the increasingly disordered mode B flow becomes the sole wake flow pattern, an empirical formula is proposed for the s Re  − relationship, i.e.

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Section: Please Cite Thismentioning

confidence: 99%

Section: Please Cite Thismentioning

confidence: 99%

Separation angle for flow past a circular cylinder in the subcritical regime

Jiang

2020

Physics of Fluids

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“…In the present experiment, the maximum temperature difference between fluid and surface is reached in the laminar flow in the valley region just before transition (the location of largestĪref/Ī in Fig. 6 a)) and is smaller than 1 K. To quantify the influence of the buoyancy forces caused by the non-adiabatic wall the Richardson number is used, see also Sabatino and Smith (2008) and Capone et al (2015). The Richardson number Ri is equal to the Grashof number Gr x divided by Reynolds number Re 2…”

Section: Errorsmentioning

confidence: 85%

“…cryogenic facilities , rotating systems (Weiss et al, 2017), and low-speed atmospheric wind tunnels (Lemarechal et al, 2018a). It has also been used for visualizations on a cylinder in crossflow in water facilities at different Reynolds numbers (Fey et al, 2013;Capone et al, 2015). In these experiments, the oscillation of the separation line and flow structures influencing the skin friction were visualized on the cylinder surface.…”

Section: Introductionmentioning

confidence: 99%

Detection of Lambda- and Omega-vortices with the temperature-sensitive paint method in the late stage of controlled laminar–turbulent transition

et al. 2019

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An experiment investigating the laminar-turbulent transition of a Blasius boundary-layer like flow was set up in the laminar water channel at the Institute of Aerodynamics and Gas Dynamics, University of Stuttgart. The late stage of controlled transition with K-type breakdown was investigated with the Temperature-Sensitive Paint (TSP) method on the flat plate surface. Additional velocity measurements in the boundary layer were performed with the hot-film anemometry for better interpretation of the TSP results. The test conditions enable the TSP method to resolve the complete transition process temporally and spatially. Therefore, it was possible to detect the coherent structures occurring in the late stage of laminarturbulent transition from the visualizations on the flat-plate surface: namely Λ-and Ω-vortices. The transition location is derived from the TSP visualizations with a gradient-based method and with the Turbulence Energy Recognition Algorithm (TERA) from the velocity measurements. The derived average transition location shows good agreement between the two techniques but the TSP method detected a later beginning and earlier end of transition.

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“…A second methodology relies on the link between the propagation celerity of temperature perturbations and the friction velocity [ 25 , 57 , 58 ]. These TSP-based methodologies have been successfully applied to identify the critical lines in low-speed flows [ 24 , 25 , 26 , 56 , 57 , 58 , 59 , 60 ].…”

Section: Introductionmentioning

confidence: 99%

Skin-Friction-Based Identification of the Critical Lines in a Transonic, High Reynolds Number Flow via Temperature-Sensitive Paint

Costantini

Henne

Klein

et al. 2021

Sensors

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In this contribution, three methodologies based on temperature-sensitive paint (TSP) data were further developed and applied for the optical determination of the critical locations of flow separation and reattachment in compressible, high Reynolds number flows. The methodologies rely on skin-friction extraction approaches developed for low-speed flows, which were adapted in this work to study flow separation and reattachment in the presence of shockwave/boundary-layer interaction. In a first approach, skin-friction topological maps were obtained from time-averaged surface temperature distributions, thus enabling the identification of the critical lines as converging and diverging skin-friction lines. In the other two approaches, the critical lines were identified from the maps of the propagation celerity of temperature perturbations, which were determined from time-resolved TSP data. The experiments were conducted at a freestream Mach number of 0.72 and a chord Reynolds number of 9.7 million in the Transonic Wind Tunnel Göttingen on a VA-2 supercritical airfoil model, which was equipped with two exchangeable TSP modules specifically designed for transonic, high Reynolds number tests. The separation and reattachment lines identified via the three different TSP-based approaches were shown to be in mutual agreement, and were also found to be in agreement with reference experimental and numerical data.

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Fast-response underwater TSP investigation of subcritical instabilities of a cylinder in crossflow

Cited by 17 publications

References 42 publications

Separation angle for flow past a circular cylinder in the subcritical regime

Separation angle for flow past a circular cylinder in the subcritical regime

Detection of Lambda- and Omega-vortices with the temperature-sensitive paint method in the late stage of controlled laminar–turbulent transition

Skin-Friction-Based Identification of the Critical Lines in a Transonic, High Reynolds Number Flow via Temperature-Sensitive Paint

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