Flow Velocimeter Noise Correction via Reference Vector Feedback
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Solution Overview
Problem
Conventional particle image velocimetry (PIV) systems face significant errors in measuring fluid flow velocity due to noise generated by particles flowing in and out of the light sheet, leading to inaccurate velocity vector calculations.
Innovation Solution
A flow velocimeter system that includes a light-sheet generation device, an imaging device, and an image analysis device with a processor, which uses cross-correlation methods to measure and correct flow velocity vectors by comparing images at different times, applying brightness corrections, and performing fast Fourier transformation to improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PIV measurement is performed without correction, then velocity vectors can be obtained, but noise errors are present due to particles flowing in and out of the light sheet
Solution Approach 1:
The patent applies feedback by using the reference flow velocity vector (obtained from previous measurements or a reference model) to correct the current flow velocity vector. The correction unit compares the current velocity vector with the reference vector and adjusts the current measurement to reduce noise errors, creating a closed-loop correction mechanism that improves reliability while maintaining measurement precision.
2Reliability
If Fourier transformation with cutoff filtering is applied to time-series velocity, then noise error at velocity vectors with large errors is reduced, but error at velocity vectors with small errors increases
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different velocity vector regions. Instead of uniformly applying filtering to all velocity vectors, the system selectively corrects velocity vectors based on their error characteristics. The correction unit identifies and corrects only those velocity vectors with large errors (noise-prone regions) while preserving the accuracy of velocity vectors with small errors, thus improving reliability without sacrificing measurement precision in accurate regions.
3Measurement precision
If flow velocity vectors are corrected using reference vectors, then measurement accuracy of time-series fluid velocity is improved, but additional processing time is required
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the reference flow velocity vector before the actual measurement and correction process. The reference vector is obtained from previous measurements or a reference model and is prepared in advance. During the measurement phase, the correction unit simply compares current velocity vectors with the pre-prepared reference vector, significantly reducing the processing time required for correction while maintaining improved measurement accuracy.
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
The system effectively reduces noise errors in flow velocity measurements, enhancing the accuracy of time-series fluid velocity data by correcting flow velocity vectors and optimizing the calculation process, especially in regions with high pixel density.
Implementation Method 1
irradiate small particles mixed in fluid with light such as laser light to acquire an image of scattered light therefrom
Implementation Method 2
measure, based on images of fluid flowing through a designated region that are formed a plurality of times at different times by the imaging device, a time-series changing mode of a local flow velocity vector of the fluid at each of a plurality of inspection regions defined at the images in accordance with a cross correlation method
Implementation Method 3
performing fast Fourier transformation to improve measurement accuracy
Data Source
AI summary
While a light sheet is generated at a designated region, images of fluid flowing through the designated region are formed at different times. For an inspection region of the plurality of inspection regions defined in the images that has a degree of difference exceeding a threshold between the local flow velocity vector v(a, b, T) at a certain time T and a reference flow velocity vector v(a, b, T±) at times T± that are different from the certain time T, the flow velocity vector v(a, b, T) at the reference time T is corrected with the reference flow velocity vector v(a, b, T±).