Submersible Electro-Acoustic Transducer Fluid Cavity Coupling
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Solution Overview
Problem
Janus-Helmholtz transducers face limitations at low frequencies, particularly in deep immersion, due to size constraints and increased hydrostatic pressure, which affects their resonance frequency and efficiency, and existing solutions like pneumatic compensation systems are limited to depths less than 3000 meters.
Innovation Solution
A submersible electro-acoustic transducer design featuring a rigid, hollow cylindrical part around a countermass, filled with immersion fluid, which couples a longitudinal piezoelectric resonance mode with a circumferential resonance mode of the cylindrical part, allowing effective acoustic coupling and reducing resonance frequency without increasing size or weight, and using suspension means for acoustic decoupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transducer uses a sealed case filled with gas to withstand hydrostatic pressure, then the transducer can operate at greater depths, but the case must be strong enough which considerably increases the weight of the transducer
Solution Approach 1:
The invention removes the gas-filled sealed case entirely and replaces it with a rigid hollow cylindrical structure filled with immersion fluid. This extraction of the gas cushion eliminates the need for heavy pressure-resistant sealing while maintaining structural integrity at depth.
Solution Approach 2:
The invention changes the fluid medium from gas to liquid (immersion fluid), fundamentally altering the physical parameters of the internal environment. This parameter change allows the structure to withstand hydrostatic pressure without requiring heavy reinforcement, as liquids are incompressible and transmit pressure uniformly.
2Reliability
If the transducer uses a rigid strong casing to withstand deep immersion pressure, then the transducer can operate at greater depths, but the transmission of acoustic waves through the casing causes losses by radiation in undesirable directions
Solution Approach 1:
The invention employs an acoustically transparent membrane instead of a rigid sealed case. This membrane is flexible enough to allow acoustic wave transmission while providing the necessary structural containment, eliminating the acoustic radiation losses that occur with rigid casings.
Solution Approach 2:
The acoustically transparent membrane acts as an intermediary between the internal fluid cavity and the external immersion medium. It allows acoustic energy to pass through freely while maintaining the structural integrity needed for deep immersion operation.
3Productivity
If the transducer uses compliant tubes filled with gas to reduce resonant frequency, then the resonant frequency decreases to between 500 and 1000 Hz, but the tubes undergo crushing at high pressures which limits the depth of immersion within 1000 m
Solution Approach 1:
The invention replaces pneumatic (gas-filled) compliant tubes with a hydraulic system using immersion fluid. The rigid hollow cylindrical structure filled with incompressible liquid provides the necessary compliance and acoustic coupling without suffering from crushing at high pressures, enabling operation beyond 1000 meters depth.
Solution Approach 2:
The invention uses a composite structure combining the rigid hollow cylindrical framework with the immersion fluid medium. This composite approach provides both the structural strength needed for deep immersion and the acoustic compliance required for low-frequency operation, overcoming the limitations of purely pneumatic or rigid structures.
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 efficient, low-frequency, high-bandwidth acoustic wave generation and transmission at great depths without pneumatic compensation, maintaining robustness and autonomy, with the transducer capable of operating below 1000 Hz and exceeding 3000 meters immersion depth.
Implementation Method 1
A Janus-Helmholtz transducer is based on the use of a stack of piezoelectric components forming a piezoacoustic motor
Implementation Method 2
said electro-acoustic motors and said cylindrical part being sized so that said fluid cavity forms an acoustic coupling between said longitudinal electro-acoustic resonance mode of said transducer and a circumferential resonance mode of said part cylindrical
Implementation Method 3
The immersed transducer transforms the vibration wave of the resonator into an acoustic pressure wave which propagates in the immersion medium
Data Source
Figure 1
AI summary
The present invention relates to a submersible electro‑acoustic transducer that can be immersed in an immersion fluid for underwater acoustic communication or for underwater acoustic tomography, said transducer comprising two horns, a counterweight, two electro‑acoustic motors, placed on either side of the counterweight, said motors being aligned along an axis of symmetry, the opposite ends of said motors being linked respectively to a horn, the assembly constituted by said electro‑acoustic motors, said counterweight and said horns being able to generate a longitudinal electro‑acoustic mode of resonance. According to the invention, said transducer comprises a rigid and hollow cylindrical piece extending around said counterweight, said cylindrical piece having an axis coinciding with the axis of symmetry of the transducer, the interior of said cylindrical piece forming a fluid cavity able to be filled by said immersion fluid, said electro‑acoustic motors and said cylindrical piece being dimensioned so that said fluid cavity forms an acoustic coupling between said longitudinal electro‑acoustic mode of resonance of said transducer and a circumferential mode of resonance of said cylindrical piece when said fluid cavity is filled with said immersion fluid.