Archivio Istituzionale della RicercaTheaerodynamicnoiseradiatedbytheflowpastacylinderinthesubcriticalregimecanbemodeledbyaquadrupolarsoundsourceplacedat theonsetpositionof thevortex-sheddinginstabilitythat isscatteredbythesurfacewithadipolardirectivity.Whenthecylinder iscoated withaporousmaterial, theintensityoftheshedvorticesisgreatlyreduced,determiningadownstreamshiftoftheinstability-outbreaklocation.Consequently, sounddiffraction is less efficient, andnoise ismitigated. In thispaper, an innovativedesignapproach for a flowpermeablecoatingbasedonafurtherenhancementof suchaneffect isproposed.Theresultsofphased-microphone-arraymeasurements showthat,oncetheleewardpartofthecoverisintegratedwithcomponentsthatmaketheflowwithintheporousmediummorestreamlined, thequadrupolarsourceassociatedwiththevortex-sheddingonsetisdisplacedmoredownstream,yieldingadditionalnoiseattenuationofup to10dBwithrespecttoauniformcoating.Furthermore, thesamenoise-controlmechanismbasedontheweakeningofthesoundscattering canbeexploitedwhenthesecomponentsareconnectedtothebarecylinderwithouttheporouscover. Inthiscase, themitigationofoverall soundpressurelevelsiscomparabletothatinducedbythecoatedconfigurationsduetothelackofnoiseincreaseproducedbytheinnerflow interactingwithintheporesof thematerial.Remarkablesoundreductionsofupto10dBandapotentialdrag-forcedecreaseareachieved withthisapproach,whichpavesthewayfordisruptiveandmoreoptimizednoise-attenuationsolutions.
Innovative coatings for reducing flow-induced cylinder noise by altering the sound diffraction / Zamponi, R.; Ragni, D.; van der Zwaag, S.; Avallone, F.. - In: PHYSICS OF FLUIDS. - ISSN 1070-6631. - 35:12(2023). [10.1063/5.0177263]
Innovative coatings for reducing flow-induced cylinder noise by altering the sound diffraction
Avallone, F.
2023
Abstract
Theaerodynamicnoiseradiatedbytheflowpastacylinderinthesubcriticalregimecanbemodeledbyaquadrupolarsoundsourceplacedat theonsetpositionof thevortex-sheddinginstabilitythat isscatteredbythesurfacewithadipolardirectivity.Whenthecylinder iscoated withaporousmaterial, theintensityoftheshedvorticesisgreatlyreduced,determiningadownstreamshiftoftheinstability-outbreaklocation.Consequently, sounddiffraction is less efficient, andnoise ismitigated. In thispaper, an innovativedesignapproach for a flowpermeablecoatingbasedonafurtherenhancementof suchaneffect isproposed.Theresultsofphased-microphone-arraymeasurements showthat,oncetheleewardpartofthecoverisintegratedwithcomponentsthatmaketheflowwithintheporousmediummorestreamlined, thequadrupolarsourceassociatedwiththevortex-sheddingonsetisdisplacedmoredownstream,yieldingadditionalnoiseattenuationofup to10dBwithrespecttoauniformcoating.Furthermore, thesamenoise-controlmechanismbasedontheweakeningofthesoundscattering canbeexploitedwhenthesecomponentsareconnectedtothebarecylinderwithouttheporouscover. Inthiscase, themitigationofoverall soundpressurelevelsiscomparabletothatinducedbythecoatedconfigurationsduetothelackofnoiseincreaseproducedbytheinnerflow interactingwithintheporesof thematerial.Remarkablesoundreductionsofupto10dBandapotentialdrag-forcedecreaseareachieved withthisapproach,whichpavesthewayfordisruptiveandmoreoptimizednoise-attenuationsolutions.
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https://hdl.handle.net/11583/2984643