Ship Speedometer Using Theoretical Curve for Deep Water Log Speed
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Solution Overview
Problem
Conventional ship speedometers, such as acoustic and multi-layered tidal current meters, struggle to measure log speeds accurately at depths where the log speed sufficiently grows, typically beyond 50 meters due to reduced signal-to-noise ratio and the influence of boundary layers and flow fields around ships.
Innovation Solution
A ship speedometer that measures current speeds at multiple depths and uses a theoretical curve to estimate log speeds in deeper ranges, where the log speed sufficiently grows, by combining actual measurement data with a pre-calculated individual-depth ship speed theoretical curve, which is updated based on measurement data and simulation techniques like Computational Fluid Dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional acoustic ship speedometers measure current speeds at multiple depths, then the boundary layer thickness can be grasped and log speed can be obtained, but measurement accuracy deteriorates at depths beyond 50 meters due to reduced signal-to-noise ratio
Solution Approach 1:
The patent introduces a theoretical curve as an intermediary to bridge the gap between measurable depths (within 50m) and the required deeper depth (100m) for accurate log speed measurement. The theoretical curve, derived from boundary layer theory and conforming to measured data, serves as a mediator that allows extrapolation to depths where direct measurement becomes unreliable due to signal degradation.
Solution Approach 2:
The patent performs preliminary actions by pre-calculating and storing theoretical curves before actual measurement operations. These theoretical curves are generated based on boundary layer theory and conforming to measured data at shallower depths, enabling accurate log speed determination at deeper depths without requiring direct measurement there, thus overcoming the signal-to-noise ratio limitation.
2Length of stationary object
If multi-layered tidal current meters or ADCP measure up to 150 meters depth, then measurement range is extended, but sufficient accuracy cannot be obtained at depths around 100 meters
Solution Approach 1:
The patent performs preliminary calculations of theoretical curves based on boundary layer theory before actual measurement. These pre-calculated theoretical curves are then used to determine log speeds at depths where direct measurement accuracy is insufficient, enabling accurate measurement at 100m depth without requiring direct measurement capability there.
Solution Approach 2:
The patent uses feedback from measurements at shallower depths to refine and conform the theoretical curves. The measured data at depths within 50 meters is used to adjust and validate the theoretical curve, which then serves as a feedback mechanism to ensure accuracy when extrapolating to deeper depths where direct measurement is unreliable.
3Measurement precision
If log speed measurement is performed at deeper ranges beyond 50 meters, then the log speed can grow sufficiently, but the influence of boundary layers and flow fields around ships becomes more significant
Solution Approach 1:
The patent extracts the harmful influence of boundary layers and flow fields by separating the measurement into two parts: direct measurement at shallower depths where the harmful influences are weaker, and theoretical calculation at deeper depths where the theoretical curve accounts for these influences. This extraction allows the log speed to grow sufficiently at depth while compensating for the harmful boundary layer effects through theoretical modeling.
Solution Approach 2:
The theoretical curve acts as an intermediary that mediates between the direct measurement data and the deeper depth requirements. It incorporates the influence of boundary layers and flow fields through boundary layer theory, allowing accurate log speed determination at 100m depth where direct measurement would be compromised by these harmful factors.
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 accurate calculation of log speeds at individual water depths up to 100 meters, where the log speed grows significantly, improving measurement accuracy beyond the limitations of conventional systems.
Implementation Method 1
a transducer that transmits ultrasonic waves into water and receives echo signals of the ultrasonic waves
Implementation Method 2
A frequency detecting unit detects the Doppler shift frequencies of those of the echo signal components at the main lobe
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
Provided is a ship speedometer which is capable of measuring log speeds at individual water depths accurately to a depth where the log speed sufficiently grows. According to a representative aspect, in a fluid where the ship floats, a speed of a current is measured at a plurality of different water depths within a given measurement range, a theoretical curve of a log speed for individual water depths, provided in advance, is conformed to a distribution of the current speeds for the individual water depths, and a log speed at an arbitrary water depth within a deeper range of the measurement range is calculated based on the conformed theoretical curve.