Air emission into a water shear layer through porous media: part 1 - scaling of bubble creation noise

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

In many industrial processes, including aeration systems and reduction of cavitation induced vibration and erosion in hydroturbine casings, it is advantageous to be able to create gas bubbles with specific size distributions, either uniform or widely distributed in diameter, depending on the situation. The induced noise and vibration associated with such systems is of increasing concern due to hearing protection standards and structural fatigue of the casing and piping. A convenient way to generate a two-phase distribution within a water pipe is to span the pipe with a streamlined surface such as a two dimensional hydrofoil and emit air through a porous medium into the shear flow over the hydrofoil. Such a hydrofoil was built and mounted in the ARL Penn State 30.5 cm diameter water tunnel. Air was introduced into a plenum within the hydrofoil which provided air evenly to the entire surface of the sintered stainless steel cover plates (20 and 100 micron porosities). Air bubbles formed at the surfaces of the cover plates through the breakdown of small jets of air issuing from the pores. The effects of the air jet size and momentum on the formation noise for a given set of conditions were evaluated by using the two different porosities of sintered metal and through the use of an array of 20, 1.2 mm diameter orifices. A variation in the shear layer was achieved by discharge through plates mounted on either the pressure or suction side of the foil. The noise due to bubble creation and transport through the highly turbulent foil wake was measured by a 2.5 cm diameter hydrophone mounted on the water tunnel window. Measurements were made at tunnel velocities of 3.1, 5.1, 7.7, and 12.3 m/sec (106 < Rechord < 4.5 × 106). Distributed area emission from a porous medium resulted in bubble creation noise levels which were 5-10 dB lower above 8 kHz and 10-20 dB lower from 3 to 8 kHz than noise levels measured during air emission at similar conditions through an array of orifices. Bubble size distributions were determined by photography. Assessments are made of the effects of discharge into the pressure or suction side boundary layers.

Original languageEnglish (US)
Title of host publicationCavitation and Gas-Liquid Flow in Fluid Machinery and Devices
PublisherPubl by ASME
Pages221-231
Number of pages11
ISBN (Print)0791813711
StatePublished - Jan 1 1994
EventProceedings of the 1994 ASME Fluids Engineering Division Summer Meeting. Part 9 (of 18) - Lake Tahoe, NV, USA
Duration: Jun 19 1994Jun 23 1994

Publication series

NameAmerican Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED
Volume190

Other

OtherProceedings of the 1994 ASME Fluids Engineering Division Summer Meeting. Part 9 (of 18)
CityLake Tahoe, NV, USA
Period6/19/946/23/94

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All Science Journal Classification (ASJC) codes

  • Engineering(all)

Cite this

Myer, E. C., & Marboe, R. C. (1994). Air emission into a water shear layer through porous media: part 1 - scaling of bubble creation noise. In Cavitation and Gas-Liquid Flow in Fluid Machinery and Devices (pp. 221-231). (American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED; Vol. 190). Publ by ASME.