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1、NATIONALADVISORYCOMMITTEEFORAERONAUTICSWARTIMEREPORTORIGINALLYISSUEDFebruary1946asAdvanceConfidentialReportL5J29aEFFECTSOFSPECIFICTYPESOFSURFACEROUGHNESSONBOUNDARY-LAYERTRANSITIONByLaurenceK.Loftin,Jr.LangleyMemorialAeronauticalLaboratoryLangleyField,Va.^^;-^^
2、?^Jk^#^?-v^W^,J8M*'*?&#-?&'*$ffis$s'*?'?*--?-'?"'?-.^--*<*WASHINGTONNACAWARTIMEREPORTSarereprintsofpapersoriginallyissuedtoproviderapiddistributionofadvanceresearchresultstoanauthorizedgrouprequiringthemforthewareffort.Theywerepre-viouslyheldunderasecurityst
3、atusbutarenowunclassified.Someofthesereportswerenottech-nicallyedited.Allhavebeenreproducedwithoutchangeinordertoexpeditegeneraldistribution.L-U831176013648812NACAACRNo.L5329aNATIONALADVISORYCOMMITTEEFORAERONAUTICSADVAN03CONFIDENTIAL-REPORTEFFECTSOF'SPECIFICTY
4、PESOFSURFACEROfOHHESS...ON;iBOUMPARY-LAYERTRANSITION-"?'.ByLaurenceK.Loftin,Jr.:SUMMARY...??Testawereconducted'withtwotypicallovb-dragair-foilsof90-inchchordtodeterminetheeffectsofsurfaceprojections*grooves,andsandingscratchesonboundary-layertransition.TheReyn
5、oldsnumber-atwhichaspanwiserowofcylindricalprojectionswould'causeprematuretransitionwasdeterminedforarangeofReynoldsnumberfromapproximately3x10"to10x10.Datawere'obtainedfor-projectionsofvarioussizesandchordwiselocationsonbothlow-dragairfoils.Theresultswereanal
6、yzedontheassumptionthatthecriticalairfoilReynoldsnumberforagivenprojectionwasafunctiononlyofthelocal-flowconditionsaroundtheprojection.Thisassumptionnegleotedpossibleeffectsoftunneltur-bulence,pressuregradient,boundary-layerReynolds?number,andtheoriginalextent
7、ofthelaminarflow.Thedatacorrelated.onthebasisofthisassumptionwithinarangeofcriticalairfoilReynoldsnumberof±0.5x106andwithinarangeofprojectionheightof±0.002inch.Thetestsofsurfaoegroovesandsandingscratchesindi-cated-that,,fortherangeofReynoldsnumberinvestigated,
8、thelaminarboundarylayerwasmuchless,sensitivetosurfaoe-groovesandsandingscratohes.-than-toprojectionsaboye-thesurfaceiINTRODUCTIONThedevelopmentoftheNACAlow-drag'airfoils,hasaroused
