 measur skin friction compress turbul boundari layer cone foreign ga inject measur skin friction compress turbul boundari layer cone foreign ga inject measur averag skin friction turbul boundari layer 15 total includ angl cone foreign ga inject measur total skin-friction drag free-stream mach number 0 3 0 7 3 5 10 inject helium air freon-12 porou wall substanti reduct skin friction realiz ga inject rang mach number test rel reduct skin friction theori--that light gase effect compar mass flow basi mark mach number reduct averag skin friction theori limit transit locat measur indic boundari layer fulli trip ga inject transit point approach forward limit increas inject variat skin-friction coeffici lower inject rate natur transit depend flow reynold number type inject ga high inject rate skin friction fair agreement turbul boundari-layer 