Fluid Surface Velocity Measurement Without Tracers
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Solution Overview
Problem
Existing methods for determining the velocity of a moving fluid surface, such as Particle Image Velocimetry (PIV), require detectable flow tracers and are limited by poor light conditions and the need for visual reference objects, which restricts installation locations and increases complexity.
Innovation Solution
A method and system using digital cameras to determine surface velocity without flow tracers, by distinguishing between 'wet' and 'dry' image regions, determining water level, and calculating surface flow velocity through image processing, allowing for flexible camera configurations and calibration without external reference points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Particle Image Velocimetry (PIV) is used to measure velocity, then velocity measurement capability is achieved, but the requirement for flow tracers and visual reference objects increases device complexity and restricts installation locations
Solution Approach 1:
The patent extracts and eliminates the requirement for flow tracers and visual reference objects from the velocity measurement system. By using natural surface features of the fluid itself (ridges, waves, patterns) as tracking markers instead of artificial tracers, and by removing the need for external reference objects, the system achieves velocity measurement without these additional components, thereby reducing device complexity and expanding installation flexibility.
Solution Approach 2:
The fluid surface serves its own measurement function by providing natural surface features (ridges, waves, patterns) that act as self-generated tracking markers. The system uses the fluid's own surface characteristics rather than requiring external tracers or reference objects, enabling the measurement system to be self-sufficient and eliminating the need for additional components.
2Measurement precision
If visual reference objects are required for camera calibration, then calibration accuracy is improved, but installation flexibility is reduced due to location constraints
Solution Approach 1:
The patent removes the requirement for visual reference objects from the camera calibration process. Instead of needing external reference objects placed at specific locations, the system performs calibration using the fluid surface features themselves and the camera's field of view, enabling installation in locations where reference objects cannot be positioned while maintaining calibration accuracy.
Solution Approach 2:
The camera system serves multiple functions: it captures images for velocity measurement, performs self-calibration using the fluid surface as a reference plane, and eliminates the need for separate calibration objects. This multi-functionality allows the system to be installed in diverse locations without requiring specific placement of reference objects.
3Measurement precision
If pixel colorimeter is used to analyze water level, then water level measurement is achieved, but measurement reliability decreases under poor light conditions
Solution Approach 1:
The patent uses colorimetric analysis of the fluid surface to determine water level and flow characteristics. By analyzing color variations in the fluid surface (which can indicate depth, flow velocity, and surface features), the system achieves reliable measurements under various lighting conditions, including poor light, by detecting color patterns rather than relying solely on brightness or intensity.
4Measurement precision
If multiple reference points are required for camera calibration, then calibration accuracy is improved, but the number of components and installation complexity increases
Solution Approach 1:
The patent eliminates the need for multiple discrete reference points by using the fluid surface itself as a continuous calibration reference. The calibration process utilizes the fluid surface features and the camera's field of view to determine calibration parameters, reducing the number of required reference points from multiple discrete objects to the fluid surface as a whole, thereby simplifying the system while maintaining calibration 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
Enables reliable and flexible measurement of surface velocity and streamflow in open channels without the need for tracers or permanent structures, functioning under various light conditions and allowing for all-year-round operation.
Implementation Method 1
A long established technique for velocity measurements is the technique of Particle Image Velocimetry (PIV)... systems which are image based possess the advantage that there is no need of expensive installations
Implementation Method 2
The method for determining the velocity comprises acquiring a sequence of images with at least one camera positioned such that the camera views a section of the water surface and a section, which is non-moving
Data Source
AI summary
A method for determining the velocity of a moving fluid surface, which comprises the following steps S1 to S5: S1) taking a sequence of images of the moving fluid surface by at least one camera; S2) comparing a first image from the sequence with a second image from the sequence in order to distinguish moving patterns of the fluid surface from non-moving parts and to obtain a first processed image (im_1f) comprising the moving patterns; S3) comparing a third image from the sequence with a fourth image from the sequence in order to distinguish moving patterns of the fluid surface from non-moving parts and to obtain a second processed image (im_2f) comprising the moving patterns; S4) comparing the first and second processed images in order to determine the spatial displacements of the moving patterns; and S5) determining from the spatial displacements the velocity.