Wind Tunnel Ship Model Resonance Control for Pitch Testing
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Solution Overview
Problem
Developing computational models of ship superstructure aerodynamics is challenging due to the presence of multiscale bluff-body features, atmospheric boundary layers, and turbulence, with a lack of experimental data for moving vessels and mechanical difficulties in producing high-frequency ship motion while maintaining low vibration and a low-friction seal between the hull and water surface.
Innovation Solution
A modeling apparatus comprising a model ship with a hull and superstructure, a water surface plane, and a resonance control mechanism, including a support structure, pitch actuation mechanism, and pitch control mechanism, which allows for oscillatory pitching motion and tuning the natural frequency to a desired value, minimizing vibration and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If subscale wind tunnel tests are conducted to achieve full scale reduced frequency, then the Reynolds number can be sufficiently high, but mechanical challenges arise in producing high frequency ship motion while maintaining low vibration and a low-friction seal between the hull and water surface plane
Solution Approach 1:
The patent applies mechanical vibration by using a pitch actuation mechanism to impart oscillatory pitching motions to the model ship at high frequencies. This resolves the contradiction by enabling the model to achieve full-scale reduced frequency conditions through controlled vibrations, thereby attaining sufficiently high Reynolds numbers for accurate aerodynamic testing without requiring full-scale dimensions.
Solution Approach 2:
The patent changes physical parameters by tuning the natural frequency of the model ship using a pitch control mechanism. This allows the system to operate at optimal frequencies that simultaneously achieve high Reynolds numbers and maintain low vibration levels, resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If high frequency ship motion is produced to achieve full scale reduced frequency, then aerodynamic testing accuracy is improved, but vibration and friction between the hull and water surface plane increase
Solution Approach 1:
The patent replaces traditional mechanical support systems with a resonance control mechanism that uses aerodynamic forces and controlled oscillations. This substitution allows high-frequency motion to be achieved while minimizing mechanical friction at the water surface interface and reducing unwanted vibrations, thereby maintaining aerodynamic testing accuracy.
Solution Approach 2:
The patent employs periodic oscillatory pitching motions at tuned frequencies to achieve full-scale reduced frequency conditions. This periodic action allows the system to operate in resonance, minimizing energy loss to vibration and friction while maintaining the high-frequency motion necessary for accurate aerodynamic measurements.
3Reliability
If realistic penetration of the water surface plane is incorporated into experimental models, then aerodynamic realism is improved, but mechanical challenges and friction increase
Solution Approach 1:
The patent implements dynamic penetration of the water surface plane by allowing the model hull to oscillate vertically and pitch within the water surface. This dynamic approach maintains aerodynamic realism by realistically representing ship-water interaction while avoiding the mechanical complexity of fixed seals, as the hull naturally penetrates and emerges from the water surface during oscillatory motion.
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 high-quality experimental wind tunnel measurements at full-scale reduced frequencies and Reynolds numbers, generating data for validating CFD models and providing new physical understanding of ship aerodynamics.
Implementation Method 1
The pitch control mechanism tunes the natural frequency of the model ship to a desired value
Implementation Method 2
The pitch actuation mechanism imparts oscillatory pitching motions to the model ship
Data Source
AI summary
Example embodiments provide a modeling apparatus comprising a model ship configured for use in a wind tunnel, the model ship comprising a hull and a superstructure, a water surface plane representing a water surface in which the model ship operates, and a resonance control mechanism comprising a support structure, a pitch actuation mechanism, and a pitch control mechanism. The support structure is connected to the model ship and provides a pitch axis about a joint traversing the model ship. The pitch control mechanism tunes the natural frequency of the model ship to a desired value. The pitch actuation mechanism imparts oscillatory pitching motions to the model ship.