An outline of the techniques available for the measurement of skin friction in turbulent boundary layers

Winter, K. G.

doi:10.1016/0376-0421(77)90002-1

Cited by 271 publications

(111 citation statements)

References 55 publications

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“…If a drop or line of oil is placed on a specularly-reflecting wind tunnel surface before a run and then subjected to'surface shear T during a run, it will flow downstream forming an inclined surface with zero thickness at the leading edge that decreases in slope with time t. From lubrication theory (8), the oil-air interface thickness y;(s, t) in the local flow direction s in the general case of varying t(s) and •u 0 (T(t)) is y;(s,t) = dt (1) Note that if i(s)-is respectively increasing, decreasing or constant, the corresponding surface is convex, concave or straight. Expansion of T(S) in a Taylor series in terms of its value at the origin gives…”

Section: Description Of Fisf Methodsmentioning

confidence: 99%

Boundary-Layer Transition and Global Skin Friction Measurement with an Oil-Fringe Imaging Technique

Monson¹,

Mateer²,

Menter³

1993

SAE Technical Paper Series

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A new oil-fringe imaging skin friction (FISF) technique to measure skin friction on wind tunnel models is presented. In the method used to demonstrate the technique, lines of oil are applied on surfaces that connect the intended sets of measurement points, and then a wind tunnel is run so that the oil thins and forms interference fringes that are spaced proportional to local skin friction. After a run the fringe spacings are imaged with a CCD-array digital camera and measured on a computer. Skin friction and transition measurements on a two-dimensional wing are presented and compared with computational predictions.

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Section: Description Of Fisf Methodsmentioning

confidence: 99%

Boundary-Layer Transition and Global Skin Friction Measurement with an Oil-Fringe Imaging Technique

Monson¹,

Mateer²,

Menter³

1993

SAE Technical Paper Series

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“…10 The sublayer fence was first suggested by Konstantinov. 10 The technique, as shown in Figure 1a, consists of a small vertical strip that protrudes into the laminar sublayer of the boundary layer and chambers for pressure reading on either side of the fence. As described in Nitsche, et al 2 , the sublayer fence technique is based on the laminar sublayer similarity law,…”

Section: Flow Around Obstaclesmentioning

confidence: 99%

Development of fiber optic aerodynamic sensors for high Reynolds number supersonic flows

Pulliam¹,

Schetz²

2001

39th Aerospace Sciences Meeting and Exhibit

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Aerospace Engineering (ABSTRACT)The purpose of the project was to examine fiber optic sensors for the measurement of pressure, skin friction, temperature, and heat flux in high Reynolds number, supersonic flow. Using a standard fiber optic signal conditioning unit (specifically a broadband interferometric system using spectra), the work centered around determining under what conditions these sensors will work effectively and quantifying the total system limitations.An interferometric-based, fiber optic skin friction sensor was developed for the measurement of wall shear stress in complex, supersonic flows. This sensor type was tested successfully in laminar, incompressible flow, and supersonic flow up to Mach 1.92, Mach 2.4 and 3.0 flow, in which the sensor operated with varying success. A micromachined, fiber optic pressure sensor was also tested in these supersonic conditions, also with varying success. The accurate operation of these sensors was found to be tied to the flow conditions and the fiber optic, signal processing system.A correlation was found to exist between the energy of the flow, either through its dynamic pressure or through external disturbances such as shocks or separation, and the noise in the signals, expressed by the variance of the gap estimate, for the pressure and skin friction sensors in these flows. The energy of the flow couples with the mechanical properties of the sensor reducing the fringe contrast of the signal used by the optical signal processing system to determine a gap estimate. As the energy of the flow is increased and the sensor is excited, the fringe contrast is reduced. A practical limit of a normalized fringe contrast of 0.10 was found for producing accurate gap estimates in real flows. A consequence is that there is a limit to the dynamic pressure of the flow for the sensors to operate accurately, which is demonstrated by the varying success of the supersonic wind tunnel tests. This correlation is sensor specific, meaning that sensors can be designed to operate successfully in any flow. Also, the signal processing system, which forms the other end of the total system, could be improved to allow accurate measurements with the current sensors.iii

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“…This procedure is commonly called "electronic test" and is a widely accepted evaluation method for hot wire anemometers. Winter [10], Haritonidis [2], Naughton and Sheplak [11], and Löfdahl and Gad-el Hak [12] have presented studies that show that actual time responses of thermal shear stress sensors cannot be predicted by electronic tests alone, and therefore tests based on the variation of flow conditions must be applied. For this purpose we used a relatively simple rotating disk shear stress calibrator.…”

Section: Experimental Arrangementmentioning

confidence: 99%

Wall shear stress hot film sensor for use in gases

Osorio¹,

Silin²

2011

J. Phys.: Conf. Ser.

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-The dynamic response of a hot-wire anemometer: III. Voltage-perturbation versus velocity-perturbation testing for near-wall hot-wire/film probes B C Khoo, Y T Chew, C J Teo et al. Abstract. The purpose of this work is to present the construction and characterization of a wall shear stress hot film sensor for use in gases made with MEMS technology. For this purpose, several associated devices were used, including a constant temperature feedback bridge and a shear stress calibration device that allows the sensor performance evaluation. The sensor design adopted here is simple, economical and is manufactured on a flexible substrate allowing its application to curved surfaces. Stationary and transient wall shear stress tests were carried on by means of the calibration device, determining its performance for different conditions. IntroductionThe study of shear stress on the walls that make the boundary of a flow is an area of great interest in Fluid Mechanics and Heat Transfer. However its measurement is complex and is generally limited to experimental models. The measurement of wall shear stresses is relevant when studying the drag of blunt or aerodynamic objects, the pressure drop through conduits, the convective heat transfer of surfaces exposed to flows, etc., but it can also be used to detect the passage of fluid-dynamic structures such as hairpin vortices, vortex shearing behind obstacles or large scale coherent structures. Having a good temporal resolution in this kind of devices is of great interest, one reason for this is that the fluctuations of wall shear are relevant in the understanding of the flow and its effect on walls. In turbulent flows, the fluctuations of shear stress reach values as high as 0.46 of the mean wall shear stress [6]. The second reason is that a slow sensor exposed to a turbulent flow yields average measurement values that do not agree with the mean shear stress. That is, the average introduced by a slow sensor is not satisfactory, requiring therefore a turbulent calibration, i.e. a calibration under the same turbulence intensity that will be found in the case to be measured. To avoid such difficulties, it is necessary to obtain measurements with good temporal resolution and eventually to estimate the average value a posteriori.A technique for wall shear stress measurement that stands out for its simplicity of implementation and accuracy is the use of thermal sensors. Thermal sensors are heaters whose electrical resistance is a function of temperature, which in turn depends on the convection heat transfer between the sensor and the flow. A trend evident in all the measurement techniques of wall shear stress is that the sensors have their sensing areas ever smaller in order to improve the temporal and spatial resolution. In this process of miniaturization micro-electro-mechanical systems (MEMS) manufacturing technology has played a central role in shear stress sensor technology [7]. MEMS technology is based on the same technology developed for semiconductor device fabrication and is w...

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An outline of the techniques available for the measurement of skin friction in turbulent boundary layers

Cited by 271 publications

References 55 publications

Boundary-Layer Transition and Global Skin Friction Measurement with an Oil-Fringe Imaging Technique

Boundary-Layer Transition and Global Skin Friction Measurement with an Oil-Fringe Imaging Technique

Development of fiber optic aerodynamic sensors for high Reynolds number supersonic flows

Wall shear stress hot film sensor for use in gases

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