Skin friction measurement on the NASA Common Research Model using global luminescent oil film skin friction meter
Accurate skin friction measurements are indispensable in the design of more efficient aerodynamic vehicles, and is also the controlling variable in closed loop flow control systems. Spatially and temporally resolved skin friction data is required to calibrate turbulence models used in Computational Fluid Dynamics analysis, and can also provide insight into the nature of near-wall turbulence. Luminescent oil film based techniques offer the ability to make distributed wall shear stress measurements with a relatively simple setup. The Global Luminescent Oil Film Skin Friction Meter (GLOSFM) technique involves calculating the shear stress based on observing the thickness of an oil film, which in turn is directly proportional to its luminescent intensity, provided the oil film is sufficiently thin. This technique is briefly reviewed, with some emphasis on uncertainty quantification, and the formation and propagation of ripples/surface waves on the oil film, as well as their impact on the shear stress measurement. Finally, this technique is used to measure the skin friction field on the wing and fuselage of the NASA Common Research Model, a passenger jet configuration. The issue of repeatability and the effects of tripping the flow are investigated, and the effect of flow parameters like the angle of attack and the Reynolds number are studied.
Sullivan, Purdue University.
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