Multilayer Groundwater Flow Sensing Using Distributed Optical Fiber
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Solution Overview
Problem
Existing methods for measuring groundwater flow velocity and direction are limited to single-point measurements, require probe movement for multi-layer assessment, cause environmental contamination, and disrupt groundwater flow, leading to poor spatiotemporal continuity and increased measurement errors.
Innovation Solution
A method using distributed optical fiber with point-source active heating to measure multi-layer groundwater flow velocity, involving steps like background temperature monitoring, active heating, data denoising, and regression analysis to estimate groundwater flow velocity without environmental contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If point source tracer dilution method or flowmeter is used, then groundwater flow velocity can be measured at a single point, but the measurement cannot be performed simultaneously at multiple points or layers without moving the probe
Solution Approach 1:
The optical fiber is divided into multiple sensing segments along its length, with each segment capable of independent temperature measurement at different depths. This segmentation allows simultaneous multi-point measurement without moving the probe, resolving the contradiction between measurement precision and time loss.
Solution Approach 2:
The measurement capability is extended from single-point (0D) to distributed multi-point (1D) along the optical fiber length. By adding the spatial dimension of measurement points, the system can measure multiple layers simultaneously, eliminating the need for probe movement and reducing time loss.
2Adaptability or versatility
If probe is raised or lowered to detect groundwater flow velocity at different depths, then multi-layer measurement is possible, but the temporal and spatial continuity of measured data deteriorates and groundwater is greatly disturbed
Solution Approach 1:
Temperature is used as an intermediary parameter to indirectly measure groundwater flow velocity. By measuring temperature distribution and its changes along the optical fiber, the system obtains continuous data without physically disturbing the groundwater, thus maintaining data reliability while achieving multi-layer adaptability.
Solution Approach 2:
The mechanical probe movement system is replaced with an optical-based distributed sensing system. Instead of mechanically moving the probe between layers, the system uses optical fiber to sense temperature at multiple depths simultaneously, eliminating mechanical disturbance and ensuring continuous reliable data.
3Measurement precision
If tracer substances are introduced into the aquifer for dilution method, then flow velocity measurement is enabled, but environmental pollution is caused
Solution Approach 1:
The natural temperature field, which is normally a background parameter, is converted into an active tracer for flow velocity measurement. By utilizing temperature as the measurement parameter, the system eliminates the need for chemical tracers that cause pollution, thus removing harmful factors while maintaining measurement precision.
Solution Approach 2:
The groundwater system's own temperature property is utilized for measurement purposes, eliminating the need for external tracer substances. The system serves itself by using its inherent thermal characteristics, thereby avoiding environmental pollution while achieving accurate flow velocity detection.
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 simultaneous multi-point and multi-layer groundwater flow velocity measurement with high precision and reduced disturbance, improving efficiency and accuracy by using temperature as a tracer and optical fiber technology.
Implementation Method 1
utilizes distributed temperature measurement optical fiber technology to test groundwater temperature attenuation
Implementation Method 2
controlling a heating device controller (3) to turn on each electric heating unit (10) for a predetermined time, so that the temperature of each groundwater monitoring point rises
Implementation Method 3
test groundwater temperature attenuation
Implementation Method 4
groundwater flow velocity estimation technology based on point-source active heating composite optical cable and groundwater multi-point heat plume attenuation
Data Source
AI summary
The present disclosure provides a method for measuring flow velocity of multilayer groundwater using distributed optical fiber with point-source active heating, comprising: setting and optimizing field test parameters; conducting a background temperature monitoring test; performing a point-source active heating distributed temperature measurement test, including conducting multiple rounds of heating tests; denoising the obtained multi-point source thermal plume attenuation signal data of the groundwater; searching for the peak value of temperature-permeability curve based on an automatic multi-scale peak search algorithm; performing secondary processing on the peak data; estimating the groundwater flow velocity. The method of the present disclosure solves the problem that the existing groundwater flow velocity measurement technology cannot simultaneously measure multiple points and multiple layers, and it can avoid groundwater contamination during the measurement process.