LAMINAR FLOW FOR SUPERSONIC TRANSPORTS
Daimler-Benz Aerospace Airbus GmbH, Bremen, Germany
Supersonic transports arc very drag sensitive. Technology to reduce drag by application of laminar flow, therefore, will be important; it is a prerequisite to achieve very long range capability. In earlier studies it was assumed that SCTs would only become possible by application of laminar flow |376|. But today, we request an SCT to be viable without application of laminar flow in order to maintain its competitiveness when laminar flow becomes available for subsonic and supersonic transports By reducing fuel burned, laminar flow drag reduction reduces size and weight of the aircraft, or increases range capability – whereas otherwise si/e and weight would grow towards infinity. Transition mechanisms from laminar to turbulent state of the boundary – layer flow (ALT, CPI. TS1) function as for transonic transports, but at more severe conditions; higher sweep angles, cooled surfaces, higher inode instabilities <HMl»must at least be taken into account, although they may not become important below Mach 3. Hitherto there is a worldwide lack of ground test facilities to investigate TSl at the expected cruise Mach numbers between 1.6 and 2.4; in Stuttgart. Germany one such facility – a Ludwicg tube – is still in the validation phase A quiet Ludwicg tunnel could be a favourable choice for Europe But it will require a new approach in designing aircraft which includes improved theoretical predictions, usage of classical wind tunnels for turbulent flow and flight tests for validation.