Measurement of Fluid Flow Velocity With High Spatial and Temporal Resolution

• US 20200132528A1
• Filed: 09/03/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: University of South Carolina
• Original Assignee: University of South Carolina
• Inventors: Wang, Guiren
• Granted Patent: US 11,674,834 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: G01F 1/206 Measuring pressure, force or momentum of a fluid flow which is forced to change its direction
• CPC Class Codes: G01F 1/661 using light
• CPC Class Codes: G01F 1/7086 using optical detecting arrangements
• CPC Class Codes: H01S 3/0007 Applications not otherwise provided for working metals or other materials by laser beam B23K26/00; using photons to produce a reactive propulsive thrust F03H3/00; optical recording of measured values in general G01D15/14; optics in general G02B; holographic processes or apparatus G03H; optical marking or sensing of data record carriers G06K7/10 - G06K7/14, G06K15/12; injection heating of plasma by laser H05H1/22; acceleration of neutral particles by electromagnetic wave pressure H05H3/04
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/02 Constructional details housings or packages of fibre lasers H01S3/06704

Abstract

The present disclosure provides methods and systems for successfully and accurately measuring the flow velocity, velocity fluctuation and velocity profile of flows of fluids with unprecedented resolution.

Claims

1. A system for time of flight velocimetry comprising:

at least one bleaching laser, wherein the bleaching laser generates at least one bleaching laser beam to bleach a dye to form a bleached blot at an initial position in a flow pathway;

at least one detection laser, wherein the detection laser generates at least one detection laser beam;

at least one dichroic mirror that reflects both the bleaching laser beam and the detection laser beam;

an objective that focuses the bleaching laser beam and the detection laser beam into two distinct focal points;

a detection system; and

a nano or micro position stage.

2. The system of claim 1, further comprising at least one mirror to reflect and direct the bleaching laser beam and detection laser beam.

3. The system of claim 1, further comprising a function generator to form either the bleaching laser beam or the detection laser beam as a pulsed beam.

4. The system of claim 1, further comprising a beam expander through which the detection laser beam passes.

5. The system of claim 1, wherein the detection system comprises at least one collection lens, at least one optical filter, at least one detection system pinhole, and at least one photodetector.

6. The system of claim 1, further comprising a camera.

7. A multiphoton laser induced fluorescence photobleaching anemometry system comprising:

at least one femtosecond or picosecond laser, which generates an excitation laser beam;

at least one beam expander;

at least one objective, which focuses the excitation laser beam;

at least one dichroic mirror;

at least one detection system;

at least one pump;

at least one fluid pathway; and

a dye solution contained in and flows along the fluid pathway after exposure to the excitation laser beam, wherein extent of photobleaching in the dye solution is directly proportional to an amount of time of exposure to the excitation laser beam.

8. The system of claim 7, further comprising at least one mirror.

9. The system of claim 7, wherein the detection system comprises at least one collection lens, at least one optical filter, at least one pinhole, and at least one photodetector.

10. The system of claim 7, further comprising multiphoton nonlinear absorption that generates fluorescence from the dye solution.

11. A multiphoton stimulated emission depletion laser induced fluorescence photobleaching anemometry system comprising:

at least one laser to generate at least one excitation beam;

at least on laser to generate at least one depletion beam;

a beam expander;

at least one dichroic mirror;

a detection system;

an objective;

a stage to control relative position of at least two laser foci points; and

a flow field.

12. The system of claim 11, further comprising a delay line to control phase between the at least one excitation beam and the at least one depletion beam.

13. The system of claim 11, further comprising at least one mirror to reflect the excitation beam and the depletion beam.

14. The system of claim 11, wherein the at least one laser generating the at least one depletion beam is a femtosecond laser.

15. The system of claim 14, further comprising an optical fiber stretching system.

16. The system of claim 11, wherein the at least one laser generating the at least one depletion laser beam is a picosecond laser.

17. The system of claim 11, wherein the detection system comprises at least one collection lens, at least one optical filter, at least one pinhole, and at least one photodetector.

18. A molecular tracer-based method to measure flow velocity, velocity fluctuation and velocity profiles comprising:

using a pulse bleaching laser to bleach a dye solution to generate a bleached blot at a first position in a flow pathway;

analyzing the fluid flow pathway with a detection beam;

using a lens to focus a pulse laser beam and the detection beam to two small foci to increase spatial resolution

detecting when the bleached blot arrives at a detection position in the fluid flow pathway; and

detecting time difference between the peak and a trough time that develops in a time series based on the flow pathway and starting of bleaching to generate the bleached blot and arrival of the bleached blot.

19. The method of claim 18, wherein extent of photobleaching in the dye solution is directly proportional to an amount of time of exposure to the pulse bleaching laser.