experimental demonstration of underwater acoustic scattering cancellation

We explore the acoustic scattering of buoyancy hollow cylinders submerged under water to eliminate the shell. A thin, low-
Shear, elastic coating is used to cancel the single pole scattering from air
For all frequencies with a wavelength greater than the diameter of the object, the filled neutral buoyancy steel shell.
By design, the uncoated Shell also has an effective density close to the water background, independently eliminating its single-pole scattering.
Due to a significant reduction in single-pole and bipolar scattering, the compliant coating results in hollow cylindrical inclusions, while the impedance and harmonic velocity match the water background.
We present the proposed cancellation method with a specific case, using a hollow cylinder array coated with a thin silicone rubber shell.
These experimental results match the prediction of finite element modeling, confirming the reduction of scattering.
Other calculations explore the optimization of the properties of silicone coatings.
Using this method, scattering cross is found
For all the wavelengths of k0a SFP = SFP 0, the slice can be reduced by 20 db. 85.
304 stainless steel pipe (ID 3. 74u2009mm/OD 4u2009mm)
The length of the mm is cut to approximate the simulated 2D HBC system.
We use commercial silicone rubber tubes (
McMaster Carl 5054K814)
The cancellation case is ID 7mm/OD 9mm and A35 Shore hardness grade.
After the initial stretch of 0.
5 length on cylinder, inflatable with 10 psi compressed air and silicone tubing lubricated with methanol is pushed to the end
Cylinders with upper limit.
The size mismatch of the silicone pipe ID/cylinder OD ensures that there is no air gap in the final coating, but the silicone wall thickness is stretched to u2009 = u2009 0. 8mmu2009±u200950u2009m.
We arrange 900 long, hollow, stainless steel cylinders in a rectangular grid of 6mm high columns, processed to the surface of a 12mm thick acrylic sheet.
These pillars provide a repeatable fixed geometric position for the arranged hollow cylinders.
The cylinder is spaced 24mm to minimize any near-
Field coupling between a single cylinder.
Juzheng Dione (PDMS)
It is then poured into the acrylic end block to prevent water from invading the sealed cylinder.
We center the spherical light source 1 with a diameter of 100mm vertically.
1 x m from the 5x3 array (un)
Coated cylinders.
Computer-controlled Velmex VXM 3-
The axis motion platform is used to locate the B & K 8103 water listener in the vertical center of the cylindrical array.
The water listener scans on a horizontal plane perpendicular to the long axis of the cylindrical array and enlarges and digitizes the collected pressure data at 10 samples/second.
The single-pole subsource is driven at 10 khz, 20 khz, 30 khz and 40 khz in 30 cycles, a sine cone, and a tone pulse.
During the event/scattering wave time overlap window, the time mean pressure amplitude is extracted from the data and corrected for the 1/strength drop of the spherical source.
In addition, Pulseto-
The pulse change of the source output amplitude was corrected with a fixed position water listener.
In analysis and finite element calculation, air-
Fill the cylinder with a steel density equal to 7850 kkgm, Young\'s modulus of 10 gpa and a Poisson\'s ratio of 0. 3.
The performance of silicone rubber used is 1020 kkgm with a compression sound speed of m/s.
The silicone rubber used has neither loss parameters nor shear modulus.
However, cut
The wave speed is 30 m/s, and the shear loss tangent is 0.
15 finite element calculation is carried out according to the measured value of similar silicone rubber (
Polydione).
The background medium is water at standard temperature and pressure.
The background plane wave occurs on the scattering body, and we solve the scattering pressure to minimize the computational error of the weak scattering field.