J. MertCDS

Daimler-Benz Aerospace Airbus GmbH, Bremen, Germany

18.1 Introduction

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.

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