1. The nonuniformity of the flow impinging on the compressionshockisthemechanismleadingto thegeneration ofthevortex.Indeed,if auniform axialflowpassesthrough anormalshock,auniform directsubsonicflow occursbehindtheshock,whereasif theincomingflow isnotuniform therecompressionshockcannolongerbestraight,neither the shockstrengthcan be constantalong the shock. As a consequencea rotationalflow occurswith velocity and entropygradients,thatbecomeslargerfor increasingflow nonuniformityupstream.Tostressthedriving roleof these gradientsratherthandirectly of theviscosity on thegenerationof thevortex,this phenomenonwascalledinviscid separation bysomeauthorsthatperformednumericalstudiesonthissubjectsincethe 1980s.9,22
2. Of course,furthervaluesof PR shouldbetestedto determinethehysteresisrange.Nevertheless,it canbenoted thatthedifferentstudiesindicatethatthetransitionbetween thetwo flow structuresoccursatC ~2.5-4 for decreasing PR and<~4-7 for increasingPR.
3. VulcainHM606(Ref. 18) >40 VulcainHM60b(present) 20-30 SubscaleJ-2s"(Ref. 1) 30
4. VulcainHM60b(present) 10-20 aExperimentalstudy;bNumericalstudy.