River Surface Flow Velocity Calculation via Variational Principle
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Solution Overview
Problem
Traditional contact methods for measuring river surface flow velocity are costly, hazardous during floods, and limited by environmental constraints, while non-contact methods like video-based flow measurement struggle with turbulence and dimensionality.
Innovation Solution
A method and device using a variational principle to calculate river surface flow velocity through image acquisition and energy functional optimization, involving calibration boards, image processing, and transformation of pixel flow fields to world coordinates, enabling precise non-contact measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact measurement methods (rotating element current meter, acoustic Doppler current profiler) are used to measure river flow velocity, then measurement capability is provided, but the system requires expensive infrastructure (cableways), poses safety risks during floods, and incurs high costs
Solution Approach 1:
The patent replaces mechanical contact measurement systems (current meters, cableways) with a non-contact optical measurement system using video cameras and image processing algorithms. The mechanical infrastructure is substituted by computational methods that analyze pixel flow fields in video sequences to calculate flow velocity, eliminating the need for physical deployment into the river and complex supporting infrastructure.
Solution Approach 2:
The patent creates a virtual copy of the physical flow field by capturing video images of the river surface and processing them into pixel flow field representations. This digital replica allows measurement of flow characteristics without direct physical contact, preserving measurement capability while eliminating the need for expensive infrastructure and safety risks associated with contact methods.
2Ease of operation
If video-based flow measurement (STIV) is used to calculate surface flow velocity, then non-contact measurement is achieved, but the method can only obtain velocity in one dimension and does not work well when turbulence intensity is large
Solution Approach 1:
The patent extends the measurement from one-dimensional velocity (traditional STIV) to two-dimensional flow velocity by analyzing pixel flow fields in both horizontal and vertical directions. The method calculates velocity components in multiple dimensions by processing image sequences and transforming pixel coordinates to world coordinates, enabling comprehensive 2D flow field characterization that works effectively even under turbulent conditions.
Data Source
AI summary
A method and device for calculating a river surface flow velocity are provided based on a variational principle, which are used to capture and process the images of an objective area, and to obtain the flow velocity field data of the objective area with high precision in a non-contact manner. The method and device include 3 steps: (1) preparation before initial flow measurement; (2) capturing a video of the river by an image acquisition device, converting a motion of a pixel flow field of the fluid in a captured image sequence into solving an energy functional optimization problem, and solving partial differential equations to obtain data of pixel flow field distribution; and (3) obtaining space coordinates of the pixel point in a world coordinate system and calculating the flow velocity according to the data obtained in the step 2 and the transformation relationship determined in the step 1.