Method of and apparatus for reducing sound generated by surfaces in fluid jet streams and the like

Claim 3

A method as claimed in claim 1 and in which said auxiliary flow is discharged through said sheet nearly parallel to said one surface of the sheet.

Claim 4

A method as claimed in claim 2 and in which said communicating is effected through a plurality of narrow paths near said free edge and running substantially parallel thereto.

Claim 5

A method as claimed in claim 1 and in which the speed of the auxiliary fluid flow is adjusted to be less than the speed of the oscillatory-pressure fluid stream.

Claim 6

Apparatus for preventing the generation of noise at the surface discontinuity provided by a free edge, such as the trailing edge, of a sheet member in an ambient fluid medium as a fluid stream leaves the confines of a fluid stream outlet, mixes with the ambient medium in a space between said outlet and said sheet member, impinges upon one surface of said sheet member, and flows over said surface as an oscillatory-pressure turbulent stream, said apparatus comprising, in combination with said outlet and said sheet member, means for producing auxiliary fluid flow at the opposite surface of said sheet member while said oscillatory-pressure fluid stream is flowing over said one surface, and aperture means disposed in said sheet member near said free edge for communicating at least part of said auxiliary fluid flow from said opposite surface through said sheet member to said one surface and generate fluid buffer layers between said one surface and said oscillatory-pressure fluid stream that decrease the impact on said free edge of the oscillatory pressures of said oscillatory-pressure fluid stream and thereby suppress noise generation thereat.

Claim 7

Apparatus for preventing the generation of noise at the surface discontinuity provided by a free edge, such as the trailing edge, of a sheet member in an ambient fluid medium as a fluid stream leaves the confines of a fluid stream outlet, mixes with the ambient medium in a space between said outlet and said sheet member, impinges upon one surface of said sheet member, and flows over said surface as an oscillatory-pressure turbulent stream, said apparatus comprising, in combination with said outlet and said sheet member, means for producing auxiliary fluid flow at the opposite surface of said sheet member while said oscillatory-pressure fluid stream is flowing over said one surface, and aperture means disposed in said sheet member near said free edge for communicating at least part of said auxiliary fluid flow from said opposite surface through said sheet member to said one surface and generate fluid buffer layers between said one surface and said oscillatory-pressure fluid stream that decrease the impact on said free edge of the oscillatory pressures of said oscillatory-pressure fluid stream and thereby suppress noise generation thereat.

Claim 8

Apparatus as claimed in claim 5 and in which means is provided for directing the auxiliary flow through said aperture means nearly parallel to the said sheet member.

Claim 9

Apparatus as claimed in claim 6 and in which said aperture means comprises a plurality of narrow slots disposed substantially parallel to said free edge and at successive regions inward of but close to said free edge, the leading edges of the said slots being contoured to guide the auxiliary flow at an acute angle to said sheet member.

Claim 10

Apparatus as claimed in claim 5 and in which the auxiliary fluid flow producing means is adjusted to produce flow speed less than the speed of the oscillatory-pressure fluid stream.