The development of optical techniques for the measurement of pressure and skin friction

Fonov, Sergey; Jones, Grant; Crafton, Jim; Fonov, Vladimir; Goss, L. P.

doi:10.1088/0957-0233/17/6/s05

Cited by 37 publications

(13 citation statements)

References 9 publications

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“…The response time of this PSP was on the order of 30 to 50 μs [ Flaherty et al , ]. Qualitative measurements were also made using a surface stress sensitive film (S3F) [ Fonov et al , ]. Markers are applied to a thin film, and the displacement is measured.…”

Section: Laboratory Setupmentioning

confidence: 99%

Flow of supersonic jets across flat plates: Implications for ground‐level flow from volcanic blasts

et al. 2014

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We report on laboratory experiments examining the interaction of a jet from an overpressurized reservoir with a canonical ground surface to simulate lateral blasts at volcanoes such as the 1980 blast at Mount St. Helens. These benchmark experiments test the application of supersonic jet models to simulate the flow of volcanic jets over a lateral topography. The internal shock structure of the free jet is modified such that the Mach disk shock is elevated above the surface. In elevation view, the width of the shock is reduced in comparison with a free jet, while in map view the dimensions are comparable. The distance of the Mach disk shock from the vent is in good agreement with free jet data and can be predicted with existing theory. The internal shock structures can interact with and penetrate the boundary layer. In the shock‐boundary layer interaction, an oblique shock foot is present in the schlieren images and a distinctive ground signature is evident in surface measurements. The location of the oblique shock foot and the surface demarcation are closely correlated with the Mach disk shock location during reservoir depletion, and therefore, estimates of a ground signature in a zone devastated by a blast can be based on the calculated shock location from free jet theory. These experiments, combined with scaling arguments, suggest that the imprint of the Mach disk shock on the ground should be within the range of 4–9 km at Mount St. Helens depending on assumed reservoir pressure and vent dimensions.

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Section: Laboratory Setupmentioning

confidence: 99%

Flow of supersonic jets across flat plates: Implications for ground‐level flow from volcanic blasts

et al. 2014

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“…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. In principle, pressure and skin-friction fields can be obtained simultaneously from the normal and tangential components of a Surface Stress Sensitive Film (S 3 F) [ 53 ], but this technique has not been applied in compressible, high Reynolds number flows yet. A major challenge for non-intrusive testing at these flow conditions may be the integration of the S 3 F into the surface of the wind-tunnel models.…”

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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“…Extension of the SSLCC technique to the general wind tunnel measurement is available in Zhao et al [ 14 , 15 , 16 , 17 ]. There are also other global wall shear stress measurement techniques, such as surface stress-sensitive film (S3F) technique [ 18 , 19 ], the oil-film interferometry (OFI) technique [ 20 ], the luminescent oil-film technique [ 21 , 22 ], the global skin friction diagnostic technique [ 23 , 24 , 25 ], and the global technique based on soft substrates [ 26 ]. The main advantage of the SSLCC technique when compared with other techniques is that the responses of SSLCC to wall shear stress are colorful and visible with a high resolution both in space, and in time, thus can immediately reveal cause-and-effect relationships between changes in model or test condition and the resulting surface shear stress field.…”

Section: Introductionmentioning

confidence: 99%

Measurement of Wall Shear Stress in High Speed Air Flow Using Shear-Sensitive Liquid Crystal Coating

Zhao

2018

Sensors

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Wall shear stress is an important quantity in fluid mechanics, but its measurement is a challenging task. An approach to measure wall shear stress vector distribution using shear-sensitive liquid crystal coating (SSLCC) is described. The wall shear stress distribution on the test surface beneath high speed jet flow is measured while using the proposed technique. The flow structures inside the jet flow are captured and the results agree well with the streakline pattern that was visualized using the oil-flow technique. In addition, the shock diamonds inside the supersonic jet flow are visualized clearly using SSLCC and the results are compared with the velocity contour that was measured using the particle image velocimetry (PIV) technique. The work of this paper demonstrates the application of SSLCC in the measurement/visualization of wall shear stress in high speed flow.

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The development of optical techniques for the measurement of pressure and skin friction

Cited by 37 publications

References 9 publications

Flow of supersonic jets across flat plates: Implications for ground‐level flow from volcanic blasts

Flow of supersonic jets across flat plates: Implications for ground‐level flow from volcanic blasts

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

Measurement of Wall Shear Stress in High Speed Air Flow Using Shear-Sensitive Liquid Crystal Coating

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