Shear stress measurement apparatus

A system for measuring shear stress comprising:

• a shear stress sensor including:
• (a) a base element adapted for placement in a wall along which a fluid flows,
• (b) a floating member for sensing a shear force of the fluid flowing along the wall,
• (c) a Fiber Bragg Grating that changes in shape and refractive index in response to a force applied to said Fiber Bragg Grating that changes the resonant frequency of said Fiber Bragg Grating, whereby the spectrum of wavelengths of light introduced to said Fiber Bragg Grating shifts,
• (d) support means, positioned between said floating member and said Fiber Bragg Grating, for:
• (1) mounting said floating member to said base element to be flush with the wall, and
• (2) transmitting a force sensed by said floating member to said Fiber Bragg Grating to change the resonant frequency of said Fiber Bragg Grating, and
• (e) optical carrier means for:
• (1) introducing light having a spectrum of wavelengths to said Fiber Bragg Grating, and
• (2) providing an indication of a shift in the spectrum of wavelengths of the light caused by a change in the resonant frequency of said Fiber Bragg Grating;
• a light source for supplying light to said optical carrier means;
• a detector for receiving light from said optical carrier means for producing an electrical signal representative of the intensity of the light received from said optical carrier means;
• and means for recording the intensity of the light received from said optical carrier means.

A shear stress sensor for measuring the shear force of a flowing fluid comprising:

• a base element adapted for placement in a wall along which a fluid flows;
• a floating member for sensing a shear force of the fluid flowing along the wall;
• a first Fiber Bragg Grating that changes in shape and refractive index in response to a force applied to said first Fiber Bragg Grating that changes the resonant frequency of said first Fiber Bragg Grating, whereby the spectrum of wavelengths of light introduced to said first Fiber Bragg Grating shifts;
• a second Fiber Bragg Grating that changes in shape and refractive index in response to a force applied to said second Fiber Bragg Grating that changes the resonant frequency of said second Fiber Bragg Grating, whereby the spectrum of wavelengths of light introduced to said second Fiber Bragg Grating shifts;
• support means, positioned:
• (a) between said floating member and said first Fiber Bragg Grating, and
• (b) between said floating member and said second Fiber Bragg Grating for:
• (a) mounting said floating member to said base element to be flush with the wall, and
• (b) transmitting a force sensed by said floating member to:
• (1) said first Fiber Bragg Grating to change the resonant frequency of said first Fiber Bragg Grating, and
• (2) said second Fiber Bragg Grating to change the resonant frequency of said second Fiber Bragg Grating;
• and
• optical carrier means for:
• (a) introducing light having a spectrum of wavelengths to said first Fiber Bragg Grating and to said second Fiber Bragg Grating, and
• (b) providing indications of shifts in the spectra of wavelengths of the light caused by changes in the resonant frequencies of said first Fiber Bragg Grating and said second Fiber Bragg Grating.

A shear stress sensor for measuring the shear force of a flowing fluid comprising:

• a base element adapted for placement in a wall along which a fluid flows;
• a floating member for sensing a shear force of the fluid flowing along the wall;
• a first Fiber Bragg Grating that changes in shape and refractive index in response to a force applied to said first Fiber Bragg Grating that changes the resonant frequency of said Fiber Bragg Grating, whereby the spectrum of wavelengths of light introduced to said first Fiber Bragg Grating shifts;
• a second Fiber Bragg Grating that changes in shape and refractive index in response to a force applied to said second Fiber Bragg Grating that changes the resonant frequency of said second Fiber Bragg Grating, whereby the spectrum of wavelengths of light introduced to said second Fiber Bragg Grating shifts;
• support means, positioned:
• (a) between said floating member and said first Fiber Bragg Grating, and
• (b) between said floating member and said second Fiber Bragg Grating for:
• (a) mounting said floating member to said base element to be flush with the wall, and
• (b) transmitting a force sensed by said floating member to:
• (1) said first Fiber Bragg Grating to change the resonant frequency of said first Fiber Bragg Grating, and
• (2) said second Fiber Bragg Grating to change the resonant frequency of said second Fiber Bragg Grating;
• and
• optical carrier means for:
• (a) introducing light having a first spectrum of wavelengths to said first Fiber Bragg Grating,
• (b) collecting light of a second spectrum of wavelength emanating from said first Fiber Bragg Grating and introducing the light having the second spectrum of wavelengths to said second Fiber Bragg Grating, and
• (c) providing indications of shifts in the spectra of wavelengths of the light caused by changes in the resonant frequency of said first Fiber Bragg Grating and changes in the resonant frequency of said second Fiber Bragg Grating.