A BRIEF ACCOUNT OF SOME UNRECORDED TECHNIQUES FOR FLOW VISUALIZATION IN FLIGHT FOR LOCATING (a) BOUNDARY LAYER TRANSITION AT ALTITUDE, (b) SHOCK-WAVE POSITION

摘要

Flow visualization techniques, which have been successfully used in flight tests, are described.nOne indicates boundary-layer transition on a wing with a "china clay" coating, that is wetted at high altitude with a liquid of suitable volatility emitted by another aircraft;the result is photographed at altitude.nThe second shows the shock-wave position by the differential rippling of a viscous oil coating on the wing;it also reveals laminar flow areas by unrippled oil, at the same time. It relies on direct sunlight but is not over-sensitive to the direction of this, within quite wide limits.