EXPERIMENTAL INVESTIGATION OF BOUNDARY-LAYER SUCTION THROUGH SLOTS TO OBTAIN EXTENSIVE LAMINAR BOUNDARY LAYERS ON A 15-PERCENT-THICK AIRFOIL SECTION AT HIGH REYNOLDS NUMBERS

摘要

The greatest difficulty was expe¬rienced throughout the investigation, however, in maintaining the sur¬faces of the model in a sufficiently good condition to prevent forward movements of the transition point. Small particles of lint, noise, and minute flows of air into the boundary layer through machined joints in the surface caused large forward movements of the transition point. In many instances transition occurred at forward positions even thou h no perceptible disturbance was found, but further rubbing and polishing of the surface restored the extent of laminar flow. The degree of surface excellence required in attempting to obtain extensive laminar layers on aircraft through the use of multiple slots would seem to be at least as high as that found necessary in the past in attempting to obtain extensive laminar layers on wings employing low-drag type of airfoil sections without boundary-layer contro1.