This paper discusses characteristic multidisciplinary issues related to quiet short takeoff and landing for civil transport aircraft with a typical short to medium range mission. The work reported here is focussing on the noise aspects and is embedded in the collaborative research centre CRC880 in Braunschweig, Germany. This long term aircraft research initiative focusses on a new transport aircraft segment for operation on airports with shorter runway length in commercial air transport. This calls for a community-friendly aircraft designed for operations much closer to the home of its passengers than today. This scenario sets challenging, seemingly contradictory aircraft technology requirements, namely those for extreme lift augmentation at low noise. The Research Centre CRC880 has therefore devised a range of technology projects that aim at significant noise reductions and at the generation of efficient and flexible high lift. The research also addresses flight dynamics of aircraft at takeoff and landing. Two companion papers, reporting about the research in the field of "Efficient high lift" 1 and "Flight dynamics" 2 complete the presentation of the CRC880. It is envisaged that in general significant noise reduction-compared to a reference turbofan driven aircraft of year 2000 technology-necessarily requires component noise reduction in combination with a low noise a/c concept. Results are presented from all the acoustics related projects of CRC880 which cover the aeroacoustic simulation of the source noise reduction by flow permeable materials, the characterization, development, manufacturing and operation of (porous) materials especially tailored to aeroacoustics, new UHBR turbofan arrangements for minimum exterior noise due to acoustic shielding as well as the prediction of jet noise vibration excitation of cabin noise by UHBR engines compared to conventional turbofans at cruise.

This paper deals with the design of an isolated axisymmetric nacelle for an Ultra-High Bypass Ratio (UHBR) engine. The intake, fan cowl, bypass duct and bypass nozzle are designed and optimized using a nacelle design system, established by combining an automated CFD analysis framework with an optimization algorithm. The optimization algorithm is based on an adaptive response surface methodology (RSM), which uses Kriging approximation to generate the surface model. The entire nacelle is parameterized using an intuitive Class shape transformation (iCST) approach. The optimization was conducted separately for the intake-cowl and exhaust system assuming minimal aerodynamic interactions between the two. The final optimized design had 26.9 Drag counts at cruise. The response surface was able to predict the cruise drag to 6% accuracy. The optimized bypass nozzle gave a maximum velocity coefficient (C V) of 0.9914 at a corresponding discharge coefficient (C D) of 0.995.

Even with different energy storage systems and power technologies of future aircraft, the thrust performance will be implemented with propulsors. In this context, the off-design nacelle behaviour – in particular for pure crosswind tests – becomes increasingly important especially for ultra-short nacelle designs due to their supposed drag and weight benefits [Peters and Rose (2015)]. In the upcoming years, several experimental tests at the Propulsion Test Facility (PTF) in Braunschweig are planned, to investigate the intake performance for different scale sizes and aspirated/powered test setups. As a starting point, two axisymmetric nacelles differing in intake length were designed and optimized at a representative full-scale fan diameter using an intuitive class/shape transformation based parametrization. The length was varied between L/D = 0.49 (classical design) and L/D = 0.36 (short design) with a minimum cruise drag design objective. The work flow of the optimization algorithm and nacelle parameter trends analysis are presented. Both intakes are scaled down to the testing rig’s diameter for the off-design analysis and a numerical setup and mesh density study are conducted. Through a detailed analysis of crosswind and scaling effects on the intake aerodynamics, the full-scale designs are modified to deliver a similar distortion behaviour for both designs by adapting the contraction ratio of the intakes. As a preparation for the upcoming tests, the numerical results of the local lip aerodynamics were analyzed for both intake designs showing, inter alia, that a decrease of the intake length increases the aerodynamic loading at the throat for the windward section.

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A CFD-based assessment of the low speed high lift performance of an over-the-wing mounted engine installations for a short range airliner with STOL capabilities is presented in this paper. The configuration is representative for a 100 passenger aircraft and characterized by pylon mounted over-the-wing installed UHBR-engines. The high lift system features active segmented and highly deflected Coanda flaps and a specifically designed droop nose at the leading edge of the wing. The study is part of the Collaborative Research Center 880 that develops technologies and configurations with quite STOL capabilities. The layout of the high lift system is described, together with the numerical approach and results for the considered test case. The objective of the present study is to investigate a short chord active plain flap in landing configuration and assess the maximum lift capabilities against target values from preliminary design studies of the CRC 880. It is a first step towards a more comprehensive assessment of variants of the high lift system. With the typical lift generation for a circulation control supported high lift system, the analysis of the stall behavior reveals a favorable smooth lift breakdown starting at the inner wing. Yet, the maximum lift properties fall short of the target value, so that an enlarged chord flap will be considered as a next step to comply with the maximum lift requirements.