Self-Similar Intermediate Structures in Turbulent Boundary L(12)

Self-Similar Intermediate Structures in Turbulent Boundary Layers At Large Reynolds Numbers

intheseexperimentstheexperimentalpointsliemuchbelowthebisectrix.Furthermore,intheseexperimentslnRe1andlnRe2di eredsigni cantly,andwethereforepickedthevalueofαthatcorrespondstolnRe1.Theresultisapairoflinesparalleltothebisectrixbutfarbelowit(Figure16e,(b)).

Moregenerally,itisverylikelythatanyoutsidecausethatincreasesthelevelofturbu-lenceshouldalsoincreasethee ectiveviscosity,andthusshiftthepointsinthe(lnη,ψ)planedownwards.AcaseinpointisthesetofexperimentsofHancockandBradshaw(1989)discussedabove,whereturbulencewascreatedbyagridinthefreestream.Theparalleldownwardshiftisindeedobserved(Figure16f),anditisofthesameorderofmagnitudeastheshiftintheexperimentsofNagibetal.NotethatintheexperimentsofNagibetal.thesecondintermediateregionisintact,anditisthereforelikelythattheshiftintheuniversaldescriptionofthe rstintermediateregionisduetothedisturbanceclosetothewall,i.e.,toroughness,justasintheexperimentofZagarolaetal.(1996).