Measurements of the wall-shear stress distribution in turbulent channel flow using the micro-pillar shear stress sensor MPS3

Liu, Yiou; Klaas, Michael; Schröder, Wolfgang

doi:10.1016/j.expthermflusci.2019.04.022

Cited by 19 publications

(11 citation statements)

References 37 publications

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“…Considering the energy spectra of the WSS gives indication of this aeroelastic behavior [12]. No distinct resonance peak appears for the current setup, which is in accordance with the findings of Liu et al [27]. Hence, no frequency limitation occurs for the investigated settings.…”

Section: Micro-pillar Shear-stress Sensor (Mps 3 )supporting

confidence: 91%

“…In previous measurements (e.g., [27]), a continuous laser light sheet was used to illuminate a plane parallel to the measurement surface exposing reflective hollow spheres that were attached to the tips of the micro pillars. This setup requires a careful adjustment of the light sheet, since large micro-pillar deflections can move the micro-pillar tip out of the illuminated plane.…”

Section: Micro-pillar Shear-stress Sensor (Mps 3 )mentioning

confidence: 99%

“…For this, a static and in-situ calibration of the MPS 3 is performed prior to the measurements. In contrast to previous approaches (e.g., [27]), the calibration is directly performed in the TCF which is going to be investigated afterwards instead of a flat-plate laminar boundary layer flow. This procedure avoids measurement errors due to variances in flow conditions between calibration and actual measurements such as different temperatures, Reynolds numbers, or sensor misalignment.…”

Section: Micro-pillar Shear-stress Sensor (Mps 3 )mentioning

confidence: 99%

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Simultaneous Stereo PIV and MPS3 Wall-Shear Stress Measurements in Turbulent Channel Flow

Mäteling

Klaas

Schröder

2020

Optics

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An extended experimental method is presented in which the micro-pillar shear-stress sensor (MPS 3 ) and high-speed stereo particle-image velocimetry measurements are simultaneously performed in turbulent channel flow to conduct concurrent time-resolved measurements of the two-dimensional wall-shear stress (WSS) distribution and the velocity field in the outer flow. The extended experimental setup, which involves a modified MPS 3 measurement setup and data evaluation compared to the standard method, is presented and used to investigate the footprint of the outer, large-scale motions (LSM) onto the near-wall small-scale motions. The measurements were performed in a fully developed, turbulent channel flow at a friction Reynolds number R e τ = 969 . A separation between large and small scales of the velocity fluctuations and the WSS fluctuations was performed by two-dimensional empirical mode decomposition. A subsequent cross-correlation analysis between the large-scale velocity fluctuations and the large-scale WSS fluctuations shows that the streamwise inclination angle between the LSM in the outer layer and the large-scale footprint imposed onto the near-wall dynamics has a mean value of Θ ¯ x = 16.53 ∘ , which is consistent with the literature relying on direct numerical simulations and hot-wire anemometry data. When also considering the spatial shift in the spanwise direction, the mean inclination angle reduces to Θ ¯ x z = 13.92 ∘ .

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Section: Micro-pillar Shear-stress Sensor (Mps 3 )supporting

confidence: 91%

Section: Micro-pillar Shear-stress Sensor (Mps 3 )mentioning

confidence: 99%

Section: Micro-pillar Shear-stress Sensor (Mps 3 )mentioning

confidence: 99%

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Simultaneous Stereo PIV and MPS3 Wall-Shear Stress Measurements in Turbulent Channel Flow

Mäteling

Klaas

Schröder

2020

Optics

Self Cite

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“…Brücker [25] used micropillar sensors to measure the topology of the wall-shear stress vector in a ZPG TBL at Re τ 940, and identified a probability of finding backflow events of around 0.05%, aligned with the results by Lenaers et al [17] at approximately the same Re. Note that micro-pillar sensors, based on correlating the deflection of small flexible pillars on the wall and the shear stress, provide accurate measurements of the τ w fluctuations (where τ w is the wall-shear stress), as well as their spatial correlations [26][27][28][29]. Thus, Brücker [25] was able to determine that backflow events are correlated with strong spanwise gradients of the wall-shear stress, and characterised the topology of critical points (defined as points where both the wall-shear stress and the surface vorticity are zero).…”

Section: Introductionmentioning

confidence: 99%

Backflow events under the effect of secondary flow of Prandtl's first kind

et al. 2020

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A study of the backflow events in the flow through a toroidal pipe at friction Reynolds number Re τ ≈ 650 is performed and compared with the results in a straight turbulent pipe flow at Re τ ≈ 500. The statistics and topological properties of the backflow events are analysed and discussed. Conditionally averaged flow fields in the vicinity of the backflow event are obtained, and the results for the torus show a similar streamwise wall-shear stress topology which varies considerably for the azimuthal wall-shear stress when compared to the pipe flow. In the region around the backflow events, critical points are observed. The comparison between the toroidal pipe and its straight counterpart also shows fewer backflow events and critical points in the torus. This is attributed to the secondary flow of Prandtl's first kind present in the toroidal pipe, which is responsible for the convection of momentum from the inner to the outer bend through the core of the pipe, and back from outer bend to the inner bend along the azimuthal direction. These results indicate that backflow events and critical points are genuine features of wall-bounded turbulence, and are not artefacts of specific boundary or inflow conditions in simulations and/or measurement uncertainties in experiments.

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“…Moreover, the oil-film based techniques cannot be applied at cryogenic conditions, and their application is obviously challenging in flight tests [ 50 ]. The Micro-Pillar Shear-Stress Sensor (MPS 3 ) [ 51 , 52 ] also enables global skin-friction measurements via a high-resolution array of micro-pillars, flush-mounted on the surface of interest. Besides the necessary surface preparation, the requirements on the micro-pillar geometry and materials currently limit their application in air flows to moderate Reynolds numbers.…”

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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Measurements of the wall-shear stress distribution in turbulent channel flow using the micro-pillar shear stress sensor MPS3

Cited by 19 publications

References 37 publications

Simultaneous Stereo PIV and MPS3 Wall-Shear Stress Measurements in Turbulent Channel Flow

Simultaneous Stereo PIV and MPS3 Wall-Shear Stress Measurements in Turbulent Channel Flow

Backflow events under the effect of secondary flow of Prandtl's first kind

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

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