Global Skin-Friction Measurements Using Particle Image Surface Flow Visualization and a Luminescent Oil-Film

Husen, Nicholas M.; Roozeboom, Nettie; Liu, Tianshu; Sullivan, John P.

doi:10.2514/6.2015-0022

Cited by 4 publications

(5 citation statements)

References 11 publications

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“…Naughton and Brown (1996) used fluorescent tracers to determine the flow direction, whereas Lunte and Schülein (2020) proposed an algorithm to calculate the skin-friction field automatically. The particle image surface flow visualization (PISFV) method (Mosharov et al 2006(Mosharov et al , 2011Husen et al 2015) uses cross-correlation analysis for the oil-flow vector determination. The global luminescent oil film (GLOF) is another oil-film-based technique developed by Liu et al (2008).…”

Section: Introductionmentioning

confidence: 99%

Feasibility of skin-friction field measurements in a transonic wind tunnel using a global luminescent oil film

et al. 2021

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The feasibility of skin-friction field measurements using the global luminescent oil-film skin-friction field estimation method was evaluated for a challenging case of a supercritical airfoil model under transonic wind-tunnel conditions (freestream Mach number of 0.72) at a high Reynolds number (10 million, based on the model chord length). The oil-film thickness and skin-friction coefficient distributions were estimated over the airfoil model upper surface for a range of angles of attack (from $$-0.4^{\circ }$$ - 0 . 4 ∘ to $$2.0^{\circ }$$ 2 . 0 ∘ ), thus enabling the study of different boundary-layer stability situations with laminar–turbulent transition, including cases with shock-wave/boundary-layer interaction. Conventional pressure measurements on the surface and in the wake of the model as well as Schlieren flow visualizations were conducted to support the oil-film based investigations. In the laminar-flow regions, the oil-film thickness could be generally kept below the critical limit of roughness that would induce premature boundary-layer transition. The skin friction in this region could be estimated with a moderate confidence level, as confirmed for portions of the chord by the reasonable agreement with numerical data obtained via laminar boundary-layer computations. Moreover, the location of transition onset was evaluated from the skin-friction estimations with relatively low uncertainty, thus enabling the examination of the transition location evolution with varying angle of attack. The estimated locations of transition onset were shown to be in general agreement with reference transition locations measured via temperature-sensitive paint. On the other hand, the oil-film thickness in the turbulent-flow regions was larger than the height of the viscous sublayer, which led to an hydraulically rough surface with increased skin friction, as compared to the clean configuration. For this reason, quantitative skin-friction estimations were not feasible in the turbulent-flow regions. The global effects of the oil-film setup on the flow around the airfoil were evaluated from the estimations of the aerodynamic coefficients. In particular, it was shown that the presence of the specific base coat used for the application of the oil film already induced a significant increase in airfoil drag, as compared to the clean configuration, whereas a thin oil film led to negligible or small additional increases in drag. Based on the present observations, considerations for the further improvement of the global luminescent oil-film skin-friction field estimation method in transonic flow experiments at high Reynolds numbers are elucidated. Graphic abstract

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Section: Introductionmentioning

confidence: 99%

Feasibility of skin-friction field measurements in a transonic wind tunnel using a global luminescent oil film

et al. 2021

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“…Global skin-friction measurements can be performed via surface-based optical methods. Techniques based on the measurement of the development of an oil film applied to the surface of interest, such as Oil-Film Interferometry (OFI) [ 28 , 40 , 41 , 42 , 43 ], Particle Image Surface Flow Visualization (PISFV) [ 44 , 45 , 46 ] and the Global Luminescent Oil Film (GLOF) [ 21 , 47 , 48 ] methods, allow for the quantitative determination of the skin-friction field. As a more qualitative technique, surface oil-flow visualization can also be a useful tool for the estimation of the locations of critical points and lines (see, e.g., [ 19 , 49 ]).…”

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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“…The evolution of a thin film of oil under the influence of shear stress has been used to determine skin friction values (Tanner and Blows 1976, Garrison and Ackman 1998, Naughton and Sheplak 2002, Naughton et al 2006, Husen 2017 and skin friction fields (Liu and Sullivan 1998, Liu et al 2008, Husen et al 2015, 2017, Husen 2017 and would be better monitored if researchers had the ability to accurately characterize the thickness distribution of a thin oil film. This article presents and demonstrates an inexpensive technique for determining spatially and temporally resolved film thickness measurements.…”

Section: Introductionmentioning

confidence: 99%

“…These luminescent film thickness measurements, however, have been made in the face of confounding spatially and temporally varying incident light. Techniques which are robust to such variations have been proposed, including the emission reabsorption laser induced fluorescence (ERLIF) film thickness measurement (Hidrovo and Hart 2001) and the background fluorescence absorption technique (Husen 2017). The former technique requires that the liquid film be optically thick, which is achievable with particularly high dye concentration or a particularly thick oil, neither of which is appropriate for the study of film thickness in some of the above motivating engineering applications.…”

Section: Introductionmentioning

confidence: 99%

“…A simple calibration technique for relating oil film luminescence to oil film thickness is also presented. This new oil film thickness measurement technique was suggested in Liu and Sullivan (1998) and was demonstrated in Husen (2017) and will facilitate quantitative studies of ripples at the liquid air interface. Also, its use when implementing the global luminescent oil film skin friction meter (Liu et al 2008) will facilitate quantitative results.…”

Section: Introductionmentioning

confidence: 99%

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The ratioed image film thickness meter

Husen

Liu

Sullivan

2018

Meas. Sci. Technol.

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A technique for measuring the thickness of a fluorescent oil film is presented. Incident light is cast upon the oil film and the intensity of the luminescent signal from the fluorescent dye is ratioed with the intensity of the incident light which is scattered from the surface of the model. The quotient is independent of the intensity of the incident light and proportional to the film thickness. Experiments are presented supporting that for sufficiently thin films the ratio is independent of the intensity of the incident light as well as independent of the angle from which the experiment is imaged and the angle from which the incident light is cast.

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Global Skin-Friction Measurements Using Particle Image Surface Flow Visualization and a Luminescent Oil-Film

Cited by 4 publications

References 11 publications

Feasibility of skin-friction field measurements in a transonic wind tunnel using a global luminescent oil film

Feasibility of skin-friction field measurements in a transonic wind tunnel using a global luminescent oil film

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

The ratioed image film thickness meter

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