Twenty-First Symposium on Naval Hydrodynamics (1997) / Chapter Skim
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Hydroacoustic Considerations in Marine Propulsor Design
Hydroacoustic Considerations in Marine Propulsor Design
Pages 898-912
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From page 898... ...
Fluid flow fields affecting marine propulsors are unsteady and give rise to time-dependent pressures which excite internal and adjacent external structures into vibrations. In the absence of cavitation, dipole sources on stationary and rotating blade rows of ship propulsors are the dominant contributors to He acoustic far field.
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From page 899... ...
The response of rotating blade rows to flow disturbances caused by upstream hydrofoils, such as stator vanes, control surfaces and other fixed appendages. The radiation consists of tonals at blade passage frequencies whose amplitudes are randomly modulated, as shown in Fig.
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From page 900... ...
FIG. 3 FREE-STREAM PROPELLER AND BAlANCE HOUSING MOUNTED IN THE WATER TUNNEL TEST SECTION .¢ In order to simplify the interpretation of the data an attempt was made to generate the simplest form of turbulence possible.
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From page 902... ...
the humps peak at a frequency slightly higher than the blade rate frequency. An understanding of these observations has been provided in recent papers by Jiang et al(8)
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From page 903... ...
Clearly, the propulsor designer will prefer an inflow containing low levels of turbulence and small correlation lengths. Subject to additional requirements such as propulsive efficiency and cavitation, he will select a low blade tip speed and a hydrofoil geometry which is non-responsive to upstream flow fluctuations.
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From page 904... ...
In this case, however, the contribution from the region of the drive point is relatively more pronounced. Kim's example demonstrates that the sound field generated by a blade row encased in an elastic shell has a complex directivity pattern, quite different from that of a dipole.
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From page 905... ...
FREQUENCIES OF MAX. RESPONSE (m=1, Ua=1, in water)
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From page 906... ...
. He considered the effects of a pressure-release coating of finite extent installed on an elastic plate located adjacent to hydroacoustic dipole sources.
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From page 907... ...
11) 907 HYDROACOUSTIC TEST FACILITIES In spite of considerable progress, current numerical techniques are not able to predict reliably the complex flow fields and time-dependent interactions which occur on the blades and nearby structures of modern propulsors.
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From page 910... ...
Although satisfactorily high Reynolds numbers are achievable even on the smaller models, full-scale geometrical dells are difficult to reproduce. The ingenious device in the 48-inch water tunnel of the ARL provides a means to acquire vibration data at larger scales.
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From page 911... ...
~~ Em_ Em_ _ FIG. 27 INSTALLATION OF TRANSDUCERS ON BLADE IN CONCLI.rSION As in the past, today's propulsor designers still rely hea lily on a combination of numerical and experimental inputs in order to meet powering, cavitation and acoustic requirements.
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From page 912... ...
3. Ffowcs Williams, J.E., " Sound Radiation from Turbulent Boundary Layers Formed on Compliant Surfaces." I
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