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Global Shear Stress
Measurement System

Global Shear Stress Measurements Over a Wedge Submerged in a Mach 4 Boundary Layer Using Shear Stress Sensitive Liquid Crystals

Shear Stress Sensitive Liquid Crystals

Shear stress sensitive Liquid Crystals (SSSLC’s) change color when subjected to a shear force. To date this technology has been previously used to qualitatively visualize the shear distribution over various three-dimensional or non-flat surfaces. Unlike encapsulated LC that are temperature sensitive, non-encapsulated LC are known to be independent of temperature and shear stress sensitive. 


ESI has developed a method for calibrating LC’s so that the resulting color change experienced  by a LC film when exposed to a shearing force can be quantitatively correlated.

Using this technology, ESI is capable of quantitatively measuring the shear stress distribution over an entire surface for a wide range of flow regimes from subsonic to hypersonic, with a; 

  • Time response of less than 1ms 

  • Spatial resolution less than 1 micron (or as accurate as the video camera being used​​​)

Screenshot 2024-05-03 at 12.03.36 PM.png

LC determination of Shear Stresses within and around downstream end of a 120x10mm yawed rectangular cavity in Mach 2 Flow.


Why Shear Stress Sensitive Liquid Crystals?

Understanding the shear stress distribution over a surface is a driving factor of all fluid dynamic analysis for aircraft design.


Although Computational Fluid Dynamics (CFD) can be used to compute the shear stress and provide insight over an entire vehicle surface; accurate experimental data must be available to first validate the necessary models employed within the CFD simulations, which, to date, is only limited to a few point measurement locations.


There are experimental visualization techniques that can be used to qualitatively infer the shear distribution over an entire vehicle surface, however, quantification of the acquired data has been unsuccessful to date.

SSSLC technology can accurately & quantitatively measure the instantaneous shear distribution over an entire aircraft or ballistic vehicle, significantly enhancing the design process.​​

Navy SBIR STP PAO Materials​​

(SBIR: Small Business Innovation Research, STP: SBIR Transition Program, PAO: Public Affairs Office)

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