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

Lemarechal, Jonathan; Klein, Christian; Henne, Ulrich; Puckert, Dominik K.; Rist, Ulrich

doi:10.1007/s00348-019-2734-1

Cited by 12 publications

(6 citation statements)

References 32 publications

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“…The transition location was defined in the present work as the location corresponding to the maximal gradient of the surface temperature within the transitional region. This choice was motivated by the coincidence found in Kreplin and Höhler (1992), Ashill et al (1996) and Lemarechal et al (2018) between this point and that corresponding to the maximal value of the root-mean-square of hot-film signals within the transitional region. The transition location was determined in a manner analogous to that discussed in Costantini et al (2016) and Costantini (2016); in the present work, however, one transition location was obtained for each bump configuration.…”

Section: Temperature-sensitive Paint (Tsp) and Tsp Data Analysismentioning

confidence: 98%

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

Costantini¹,

Risius²,

Koch³

et al. 2019

Experimental Thermal and Fluid Science

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The influence of surface bumps on boundary-layer transition was experimentally investigated in the present work. The experiments were conducted in a (quasi-) two-dimensional flow at low to high subsonic Mach numbers and chord Reynolds numbers up to 10 million in the low-turbulence Cryogenic Ludwieg-Tube Göttingen. Various streamwise pressure gradients relevant for natural laminar flow surfaces were examined. Quasi-two-dimensional bumps, with a sinusoidal shape in the streamwise direction, fixed length and three different heights, were installed on a two-dimensional flat-plate model. The model was equipped with temperature-sensitive paint for non-intrusive transition detection and with pressure taps for the measurement of the surface pressure distributions. Boundary-layer transition was shown to occur at a more upstream location with increasing bump height-to-length ratio. This was mainly due to the local adverse pressure gradient on the downstream side of the bump, which was particularly pronounced in the case of the bump with the largest height-to-length ratio, thereby inducing boundary-layer separation (as verified via oil-film visualizations). In the case of the bump with the smallest height-to-length ratio, bumpinduced transition was found to be dependent on global pressure gradient, Mach number and Reynolds number; however, the influence of these parameters on transition induced by bumps with larger height-tolength ratios was significantly reduced. The sensitivity of boundary-layer transition to the effect of the bumps was shown to be more pronounced with stronger global flow acceleration and at smaller Mach numbers.

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Section: Temperature-sensitive Paint (Tsp) and Tsp Data Analysismentioning

confidence: 98%

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

Costantini¹,

Risius²,

Koch³

et al. 2019

Experimental Thermal and Fluid Science

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“…Since the forced-convection heat transfer coefficient is generally a function of the skin friction, the imposed flow-surface temperature difference is transferred at different rates depending on the local skin friction, thus leading to augmented surface temperature variations that can be measured by means of TSP. The surface heat flux can be imposed through a variety of methods reported in previous work [ 25 , 60 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ].…”

Section: Applied Methodsmentioning

confidence: 99%

“…In this work, the surface heat flux was imposed via two different types of electrical heating systems integrated beneath the TSP: a layer of Carbon NanoTubes (CNT) [ 65 , 70 , 71 , 72 ] and a current-carrying carbon fiber layer [ 64 , 73 , 74 ]. The integration of these electrical heating layers in the TSP layer composition was specifically designed for the examined test conditions in a transonic wind tunnel, as described in Section 3.2 .…”

Section: Applied Methodsmentioning

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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“…From the gray values on the surface grid the location of laminar-turbulent transition can be derived at the location of largest gradient Lemarechal et al (2019). The measured gray values are spatially me-dian filtered in flow direction.…”

Section: Data Acquisitionmentioning

confidence: 99%

Investigation of stationary-crossflow-instability induced transition with the temperature-sensitive paint method

Lemarechal

Costantini

Klein

et al. 2019

Experimental Thermal and Fluid Science

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The Temperature-Sensitive Paint (TSP) method is used for surface-based flow visualizations on a swept-wing wind-tunnel model with a generic natural laminar-flow airfoil. Within the investigated parameter range the stationary crossflow instability is the dominating instability mechanism. Based on the TSP results the location of the laminar-turbulent transition and the most amplified wavenumber of the stationary crossflow instability are determined. The test is performed with three different conditions of the leading-edge surface: highly polished, unpolished, and highly polished with discrete roughness elements applied. The Temperature-Sensitive Paint method has proven to have sufficient spatial resolution and temperature sensitivity to resolve skin friction variations to detect the footprint of stationary crossflow vortices even inside of turbulent wedges. With the discrete roughness elements, i.e. cylindrical elements with micron-sized height, the transition could be delayed successfully for certain conditions. Local low-frequency movement of the beginning of turbulent wedges was detected for some data points with an unpolished leading edge.

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

Cited by 12 publications

References 32 publications

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

Experimental study of bump effects on boundary-layer transition in compressible high Reynolds number flow

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

Investigation of stationary-crossflow-instability induced transition with the temperature-sensitive paint method

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