NATURAL LAMINAR-FLOW WING CONCEPT FOR SUPERSONIC TRANSPORTS

A ''reverse'' delta wing, having a straight leading edge and forward-s wept trailing edges, is shown to be capable of achieving extended runs of natural laminar now during supersonic flight. Euler calculations a t supersonic Mach number confirm that the flow over a reverse delta wi ng is nominally two dimensional, in contrast to delta wing flow that e xhibits large spanwise flow gradients, particularly near the leading e dge. The data suggest that crossflow and attachment line instabilities , the primary modes of transition on swept wings, are minimal on a rev erse delta wing. Predicted forces on 2% thick delta and reverse delta wings are in accord with the principles of reciprocal now theory becau se lift-curve slope, wave drag, and drag-due-to-lift are nearly identi cal. The reverse delta wing has a large aerodynamic center shift as Ma ch number increases from subsonic to supersonic. Subsonic wind-tunnel tests were conducted with a variety of leading- and trailing-edge flap planforms to assess the longitudinal characteristics of a reverse del ta wing. The experimental data show that leading-edge flaps are highly effective at increasing maximum lift and decreasing drag at moderate angles of attack. Trailing-edge flaps were up to 90% as effective as d elta wing naps in generating untrimmed lift increments.