𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Holographic sensor for measurement of wall velocity gradients

✍ Scribed by J. E. Millerd; J. P. Swienton; F. Unterscher; J. D. Trolinger; L. G. Smith; J. C. LaRue

Publisher
Springer
Year
1996
Tongue
English
Weight
861 KB
Volume
21
Category
Article
ISSN
0723-4864

No coin nor oath required. For personal study only.

✦ Synopsis

Time-resolved measurements of skin friction and boundary layer turbulence are important to the design of more fuel efficient aircraft. In this paper we describe the design and testing of a holographic fan fringe sensor that can non-intrusively measure time-resolved velocity gradients near an aerodynamic surface. The holographic sensor produces a set of optical interference fringes inside the viscous sub-layer that form a fan rather than a linear array. Particles scattering light in the sub-layer produce a Doppler frequency that is a direct measurement of the velocity gradient and is proportional to aerodynamic shear stress and skin friction. The holographic recording condenses the optics necessary to form the fringes into a small 3-5 mm package, eliminates the need for optical access from behind the model, and produces a compact and robust sensor.

πŸ“œ SIMILAR VOLUMES

Measurement of turbulent wall velocity g
Measurement of turbulent wall velocity gradients using cylindrical waves of laser light
✍ A. A. Naqwi; W. C. Reynolds πŸ“‚ Article πŸ“… 1991 πŸ› Springer 🌐 English βš– 817 KB

A new optical instrument has been developed for direct measurement of instantaneous velocity gradients at the bounding wall. Light emerging from two tiny optical slits in the surface is used to form a "fan of fringes" in the region very near the wall. Doppler frequency of the light scattered by the

Electrochemical measurement of velocity
Electrochemical measurement of velocity gradient at the wall of a helical tube
✍ Sylvain Galier; SΓ©bastien Issanchou; Philippe Moulin; Michael J. Clifton; Philip πŸ“‚ Article πŸ“… 2003 πŸ› American Institute of Chemical Engineers 🌐 English βš– 575 KB

## Abstract An electrochemical technique was used for measuring the wall velocity gradient in two coiled pipes: a torus and a helix. An electrochemical oxidation reaction was employed with its rate limited by mass transfer. Measurement of the diffusion‐limited current at a microelectrode embedded f