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.

A quantitative global skin-friction measurement technique is proposed. An oil-film is doped with a luminescent molecule and thereby made to fluoresce in order to resolve oil-film thickness. Particle Image Surface Flow Visualization (PISFV) is used to resolve the velocity field of the surface of the oil-film. Skin-friction is then calculated at location � �⃗ as (� �⃗) = � �⃗ (� �⃗, )/ (� �⃗, ), where � �⃗ ( , ) is the velocity field of the surface of the oilfilm, is the thickness of the oil-film, is time, and is the dynamic viscosity of the oil. The data collection and data analysis procedures are explained, and preliminary experimental skin-friction results for flow over the wing of NASA's Common Research Model are presented.

No abstract

This paper further develops the global luminescent oil-film skin-friction meter by considering its application to a three dimensional axisymmetric wall-mounted bump subjected to subsonic turbulent boundary layer flow. The geometry gives rise to a necklace vortex and large scale separation on its lee side. An oil-film is only usable by the global luminescent oil-film skin-friction meter if it meets certain criteria. Most notably, it must be sufficiently thick to provide a good signal but not so thick that the relationship between luminescent intensity and oil-film thickness becomes nonlinear. Different regions on the model give rise to a usable oil-film at different times in an experiment. This paper proposes a technique for the selection of which solutions from a sequence of "snapshot solutions" taken during the run should be averaged for a particular region on the model. A relative skin-friction distribution resulting from the techniques proposed herein is presented for each of four sections of the model: One down the model's centerline, and three across the model in the spanwise direction. Nomenclature y = height of model H = total height of model ℎ = thickness of oil film r = radial distance from origin ( 1 , 2 , 3 ) = global coordinate system in object space ( ̅ 1 , ̅ 2 , ̅ 3 ) = coordinate system with 1-2 plane locally tangent to surface (̃1,̃2,̃3) = coordinate system with 1-2 plane parallel with image plane S = function describing surface of model in ( 1 , 2 , 3 ) coordinates ̃ = function describing surface of model in (̃1,̃2,̃3) coordinates t = time p = static pressure of external flow field = dynamic viscosity of oil-film = density of oil-film = -th component of gravity = -th component of skin-friction = change of coordinate matrix I = Intensity of luminescent oil-film = Intensity of the excitation light incident on the oil-film = coefficient proportional to quantum efficiency of luminescent molecules = skin-friction ̅ = equivelant skin-friction = Lagrange multiplier Downloaded by UNIVERSITY OF QUEENSLAND on October 8, 2015 | http://arc.aiaa.org |

No abstract