Optical probe for measuring wall-shear stress
Aspects of this disclosure are directed to optical probes for collecting images of a region of interest for determining wall shear stress. The optical probe includes an imager with a line of sight and a light guide configured to steer light from a light source to the region of interest. The optical probe includes an objective configured to focus light reflected off of the region of interest to the line of sight of the imager. The optical probe can include a micro-lens array at the objective. The micro-lens array can focus light from the objective onto the imager. The imager can collect images from the light from the micro-lens array for determining wall shear stress at the region of interest.
1 . A system for measuring wall shear stress within a region of interest, the system comprising:
an optical probe for collecting images of the region of interest, the optical probe comprising:
an imager with a line of sight;
a light guide configured to steer light from a light source to the region of interest;
an objective configured to focus light reflected from the region of interest to the line of sight of the imager, wherein the imager is configured collect images from the light from the objective;
a micro-lens array at the objective, the micro-lens array configured to focus light from the objective onto the imager, wherein the micro-lens array is configured to subsample the region of interest at different perspective angles; and
a processor configured to determine wall shear stress at the region of interest from the images, and to generate a three-dimensional image from the subsample.
2 . The system of claim 1 , wherein the processor is configured to resolve near-wall velocity gradients at the region of interest.
3 . The system of claim 1 , wherein the processor is configured to determine wall shear stress at the region of interest from the images using molecular tagged velocimetry.
4 . The system of claim 1 , wherein the processor is configured to determine wall shear stress at the region of interest from the images using particle image velocimetry or particle tracking velocimetry.
5 . The system of claim 1 , further comprising tracers injected into fluid flowing through the region of interest.
6 . The system of claim 1 , wherein the processor is configured to infer the wall shear stress from sparse velocity fields within the image.
7 . The system of claim 1 , wherein the processor is configured to resolve near-wall flow motion at a desired spatio-temporal resolution.