Project Title:

A Quantitative Skin Friction Imaging Sheet

02.08-0003
912284
A Quantitative Skin Friction Imaging Sheet
Physical Sciences, Inc.
20 New England Business Ctr
Andover
MA
01810
R. Daniel
Ferguson
508-689-0003
LaRC
NAS1-19534
022

02.08-0003
912284

Abstract:

Optical techniques have been employed in attempts to gain a qualitative picture of
the skin friction distribution over surfaces. The methods based upon coatings which
exhibit shear-stress-sensitive properties have limited dynamic range. They require
external imaging systems that render them less suitable for aeronautical applications.
New thermal-type imaging approach offers the potential of high-resolution, CCD-style
readout and display of skin-friction data in real time without the need for external
optical diagnostics, and will be developed for large-area (1 m2) wind-tunnel instrumentation
and aeronautical applications. The proposed device would consist of an array of a
new type of thermal, shear-stress sensor integrated into a thin, flexible skin. High-sensitivity,
flexible, pyroelectric sensors that accumulate charge in proportion to local temperature
changes can monitor local surface cooling rates after known heat pulses are delivered
by underlying heating films. This cooling rate has a simple relationship to the skin
friction. Standard "V"-type sensor configurations can separate the wall shear stress
components in cross-flow conditions. The skin friction would read out in a manner
similar to CCD-array cameras. Such a sheet could be readily attached to any surface
and the skin friction monitored and displayed continuously in, for example, standard
RGB video format.
A non-intrusive, skin-friction CCD 'camera' has the potential to become a commercial
product usable in fluid dynamics laboratories around the world. These distributed
sensor arrays can be installed on aircraft wings with outputs coupled to control
system which improve aerodynamic performance. Active control strategies can be developed
for turbulence, flow separation and cross-flow problems, where rapid assessment of
extended flow-field topology is critical.
skin friction, imaging, turbulence, instrumentation, diagnostics