Flow Velocity Distribution Measurement Using Tracer Particles
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Solution Overview
Problem
Current methods for measuring flow velocity distribution inside an optical cell are inaccurate due to the effects of Brownian motion and hydrodynamic interactions, especially at the microscale, and increasing particle density to improve accuracy leads to increased viscosity and pressure loss, distorting the flow field.
Innovation Solution
A microscale particle tracking velocimetry method using a laser beam to visualize tracer particles as bright spots, allowing for accurate measurement of flow velocity distribution without direct observation of particles, and correcting for Brownian motion to improve measurement sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number density of tracer particles is increased to improve measurement accuracy, then the measurement precision of flow velocity distribution is improved, but the viscosity of the fluid increases and pressure loss increases, distorting the flow field
Solution Approach 1:
The patent changes the physical parameters of tracer particles by using particles with different material compositions (e.g., fluorinated particles, gold particles, quantum dots) and size distributions. This allows optimization of particle properties to reduce hydrodynamic interactions while maintaining sufficient scattering signal for accurate flow velocity measurement.
Solution Approach 2:
The patent introduces specific types of tracer particles as intermediaries that have optimized properties - they are sufficiently small to minimize flow disturbance but have enhanced light scattering properties (through materials like gold, quantum dots, or fluorinated compounds) to enable accurate tracking. This mediator approach resolves the contradiction between measurement precision and flow field distortion.
2Object-affected harmful factors
If the size of tracer particles is decreased to reduce flow field distortion, then the distortion of flow field is reduced, but the measurement sensitivity decreases making particles harder to detect
Solution Approach 1:
The patent changes the optical parameters of tracer particles by using materials with high refractive index contrast (gold particles, quantum dots, fluorinated particles) or by modifying particle surface properties. This allows submicron particles to maintain low flow disturbance while providing sufficient light scattering signal for detection.
Solution Approach 2:
The patent replaces conventional optical microscopy with advanced detection methods including fluorescence microscopy, dark-field microscopy, or interferometric techniques. This substitution enables detection of smaller particles with lower light scattering cross-sections, resolving the contradiction between particle size and detectability.
3Measurement precision
If the interparticle distance is decreased by increasing particle density, then the measurement precision is improved, but hydrodynamic interactions between particles increase affecting measurement accuracy
Solution Approach 1:
The patent changes the size parameter of tracer particles by using smaller particles (submicron size) that can be placed closer together without significant hydrodynamic interaction. The enhanced optical contrast of these smaller particles compensates for the reduced interparticle distance, maintaining measurement precision while minimizing particle-particle interference.
4Device complexity
If conventional light scattering observation is used to detect tracer particles, then the device complexity is low, but the measurement sensitivity is insufficient for submicron particles
Solution Approach 1:
The patent changes the optical properties of tracer particles by using materials with enhanced light scattering or fluorescence properties (gold particles, quantum dots, fluorinated particles). This allows conventional or mildly enhanced microscopy systems to achieve high detection sensitivity for submicron particles without requiring complex detection apparatus.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise measurement of flow velocity distribution and particle size in a flow field with reduced distortion and increased sensitivity, allowing for accurate measurement of submicron particles without affecting the flow field.
Implementation Method 1
a laser light irradiation unit 6 irradiating laser light 6a of a single wavelength λ to the particles 2 inside the optical cell 5... capturing unit 8 including a camera 8a capturing the inside of the flow passage... capturing a bright spot attributed to the light scattering from tracer particles
Implementation Method 2
the effect of a random displacement caused by Brownian motion cannot be ignored... correcting for Brownian motion to improve measurement sensitivity and accuracy
Data Source
AI summary
A measuring method enabling simple and accurate measurement of a flow velocity distribution in a flow field inside a flow passage of an optical cell and a particle size-measuring method using the measuring method are provided. Providing a tracer particle of a smaller size than wavelength λ of laser light into the flow passage and capturing a bright spot attributed to light scattering from tracer particles by camera, and obtaining the flow velocity distribution by the analysis unit by obtaining an amount of movement of each tracer particle from movement of the bright spot and correcting a Brownian motion component from a correlation between an average value of variations of the amount of movement and Brownian motion are performed.