The motion of a thin oil sheet under the steady boundary layer on a body

Squire, L. C.

doi:10.1017/s0022112061000445

Cited by 118 publications

(51 citation statements)

References 2 publications

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“…It only requires calibration between image space and physical space and can be used to obtain the wall shear stress without any knowledge or assumptions about the flow field. This technique was first introduced by Tanner and Blows (1976), who developed a simple relationship to measure shear stress using the thin oil-film equation developed by Squire (1961). Image-based technique, here, is one of the several variations from the original form proposed by Tanner and Blows (1976).…”

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confidence: 99%

Skin-friction measurements in a turbulent boundary layer under the influence of free-stream turbulence

et al. 2017

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increasing FST is known to increase skin friction and to enhance heat transfer (Hancock and Bradshaw 1989;Blair 1983). However, a large number of previous studies focused on the correlation between the increase of skin friction and heat transfer with FST. Hancock and Bradshaw (1989) showed that the effect of FST in the turbulent boundary layer does not only depend on the turbulence intensity level but on a characteristic scale in the FST, which they defined as the dissipation length scale. However, skin-friction coefficients were deduced from logarithmic plots on the assumption that the universal logarithmic law also applies in the presence of FST. Thole and Bogard (1996) performed extensive research on FST levels up to 20% and presented boundary layer statistics that confirmed the validity of the logarithmic law in the mean profiles of the boundary layer for high turbulence levels by comparing direct measurements of total shear stress with values obtained using a Clauser fit to the log region. Similarly, Stefes and Fernholz (2004) compared skin-friction data obtained from oil-film interferometry (OFI), wall hot wire, and Preston tube at relatively high Reynolds numbers and FST levels up to 13%, showing that all skin-friction data points lied within an error band of approximately 6% on C f .Traditional indirect pressure-based methods, such as the Preston tube, rely on the law of the wall and suffer from limitations arising from its intrusive nature. Velocity profile-based methods such as Clauser chart are also of limited applicability, since they also assume the existence of the law of the wall and require the knowledge of its extent and constants beforehand. Contrarily, Rodríguez-López et al. (2015) proposed to leave these constants free to adopt the value that best fits the data. In addition, this method does not require to prescribe the extent of the logarithmic layer (which can vary under FST conditions, see Dogan et al. 2016) and allows a certain uncertainty in the wall-probe initial position.Abstract This experimental investigation deals with the influence of free-stream turbulence (FST) produced by an active grid on the skin friction of a zero-pressure-gradient turbulent boundary layer. Wall shear stress is obtained by oil-film interferometry. In addition, hot-wire anemometry was performed to obtain wall-normal profiles of streamwise velocity. This enables the skin friction to be deduced from the mean profile. Both methods show remarkable agreement for every test case. Although skin friction is shown to increase with FST, the trend with Reynolds number is found to be similar to cases without FST. Furthermore, once the change in the friction velocity is accounted for, the selfsimilarity of the logarithmic region and below (i.e. law of the wall) appears to hold for all FST cases investigated.

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confidence: 99%

Skin-friction measurements in a turbulent boundary layer under the influence of free-stream turbulence

et al. 2017

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“…This principle finds its mathematical expression in the thin-film theory that is used to quantify the skin friction from the measurements of the oil-film technique. 25 The key relation is the one that links the height of the oil film, h, to the shear stress, τ w …”

Section: Technique For Skin Friction Measurementsmentioning

confidence: 99%

Design and qualification of a supersonic wind tunnel for induced boundary layer transition research

Bottini

Paniagua

Schreivogel

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part G:

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This paper presents the design and the results of the qualification test campaign of a multiple-Mach-number supersonic wind tunnel designed for induced boundary-layer transition. Its characteristics, function, and instrumentation are described. The range of Mach numbers successfully span is presented along with the measured intensities of freestream fluctuations. All the measurement techniques implemented in the test campaigns after the qualification are introduced, and some results shown and commented to highlight their potentialities.

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“…Figure 10 only displays the luminescent oil flow results at representative angles of incidences (i.e., 0, 6 and 12 degrees) viewed from the top. According to Squire's analysis, 43 the direction of the oil movement is believed to correlate to the wall shear stress and the pressure gradient. Generally, the oil streaks are longer on the conical surface than the cylinder segment, which corresponds to the high shear stress on the conical surface.…”

Section: B Surface Flow Patternmentioning

confidence: 99%