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dc.contributor.authorRusche, Max Thomasen_US
dc.date.accessioned2014-03-14T20:44:13Z
dc.date.available2014-03-14T20:44:13Z
dc.date.issued2011-07-28en_US
dc.identifier.otheretd-08252011-081702en_US
dc.identifier.urihttp://hdl.handle.net/10919/34773
dc.description.abstractMeasurements were made in a zero pressure gradient turbulent boundary layer over two roughness patches containing hemispherical and cubical elements. The elements were 3 mm in height and spaced 16.5 mm apart in an array containing 7 streamwise rows and 6 spanwise columns for a total of 42 elements per patch. The boundary layer thickness was approximately 60 mm, so the ratio of element height to that thickness was a large amount at k= = 1=20. A three velocity component laser Doppler velocimeter measured instantaneous velocities. Mean flow and turbulence statistics were calculated as well velocity energy spectra. Surface pressure fluctuations were measured using a two-microphone subtraction method. The results show that hemispherical elements produce larger turbulence quantities in their wakes compared to the cubes. This is due to the hemispheres having a frontal area nearly 60% larger than that of the cubes. The turbulence levels behind the hemispheres is a maximum behind the first streamwise row of elements, and decreases afterwards. The cubical elements maintain a nearly constant amount of turbulence in their wake, signifying little interaction between cubical elements. Surface pressure fluctuations vary little in the streamwise direction of the patches. The hemispherical elements produce a larger sound pressure level behind them than the cube elements do. Velocity spectra results show large normal stress energy for regions at and below the element height. The energy for locations high in the boundary layer increases as the flow moves downstream. Coherency plots show that there is a large correlation between the turbulent structure and production of shear stress at the roughness height. Any measurements taken at or below the roughness height are highly correlated under 10 kHz, while locations higher in the boundary layer are correlated under 2 kHz.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartRusche_MT_T_2011.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectturbulenceen_US
dc.subjectroughnessen_US
dc.subjectsurface pressureen_US
dc.subjectvelocity spectraen_US
dc.subjectboundary layeren_US
dc.titleStructure of Turbulent Boundary Layers and Surface Pressure Fluctuations on a Patch of Large Roughness Elementsen_US
dc.typeThesisen_US
dc.contributor.departmentAerospace and Ocean Engineeringen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineAerospace and Ocean Engineeringen_US
dc.contributor.committeechairSimpson, Roger L.en_US
dc.contributor.committeememberSchetz, Joseph A.en_US
dc.contributor.committeememberDevenport, William J.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08252011-081702/en_US
dc.date.sdate2011-08-25en_US
dc.date.rdate2011-09-16
dc.date.adate2011-09-16en_US


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