Raindrop Diameter Measurement Using Ellipsoidal Model
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Solution Overview
Problem
Optical disdrometers used to measure raindrop diameter exhibit a bias that increases with drop size, affecting the accuracy of precipitation rate measurements.
Innovation Solution
A method and device that measure the equivalent diameter of raindrops by using an ellipsoidal model, accounting for the actual shape of raindrops rather than assuming spherical shape, and applying empirical relationships to correct for bias, involving the use of two laser beams and optical receivers positioned at specific angles to capture light intensity signals and time shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a spherical model is used to measure raindrop diameter, then the measurement process is simple, but the measurement precision deteriorates due to bias increasing with drop size
Solution Approach 1:
The patent changes the geometric model parameter from spherical to ellipsoidal, adapting the shape assumption to match actual raindrop morphology. This parameter change resolves the contradiction by maintaining measurement simplicity while eliminating the size-dependent bias that plagues spherical models, thereby improving accuracy without significantly complicating the measurement process.
Solution Approach 2:
The patent introduces dynamic adjustment of the ellipsoidal model parameters based on measured data, allowing the model to adapt to different drop sizes and shapes. This dynamic approach maintains simplicity by using a systematic methodology while improving precision across the full range of raindrop sizes through adaptive parameter optimization.
2Measurement precision
If an ellipsoidal model is used to account for actual raindrop shape, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by transitioning from a spherical to an ellipsoidal model, which better represents actual raindrop geometry. This change improves measurement accuracy by accounting for the flattened shape of real raindrops while managing complexity through systematic parameter relationships that simplify the computational burden.
Solution Approach 2:
The patent segments the measurement process into distinct computational steps: measuring equivalent diameter from light intensity signals, calculating volume from the ellipsoidal model, and deriving actual dimensions from volume and equivalent diameter. This segmentation manages complexity by breaking down the sophisticated ellipsoidal modeling into manageable, sequential operations.
3Ease of manufacture
If spherical assumption is made for raindrops, then calculation is simplified, but bias increases with drop size affecting precipitation rate measurements
Solution Approach 1:
The patent changes the fundamental geometric parameter from spherical to ellipsoidal modeling, which eliminates the size-dependent bias in precipitation rate measurements. This parameter change maintains calculation simplicity through systematic relationships while significantly improving reliability by accurately representing the flattened shape of actual raindrops across all size ranges.
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
Improves the accuracy of raindrop diameter measurements by accounting for the non-spherical shape of raindrops, reducing bias and enhancing the precision of precipitation rate calculations.
Implementation Method 1
This measurement is based on the analysis of the light intensity of the refracted signals received by the optical receivers during the passage of a drop of water through the laser beam(s) generated by the laser source.
Data Source
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AI summary
The invention relates to a method for measuring the equivalent diameter of a water droplet comprising: - a step of obtaining a first light intensity signal at a determined angle in a horizontal plane and a step of obtaining a second light intensity signal at said determined angle in a vertical plane, said light intensities being modulated by the passage of said water droplet through at least two laser beams emitted by a laser source; - a step of measuring a first time shift between the two largest intensity maxima of one of said intensity signals; - a step of measuring a second time shift between said first and said second intensity signal;- a step of calculating the equivalent diameter of said water droplet from an ellipsoidal model of said water droplet, a non-constant law relating the ratio of the two axes of said ellipsoidal model to the equivalent diameter of said model, of said first and of said second time shift.;