Preliminary design studies indicate that a cruise-efficient short takeoff and landing aircraft has enhanced takeoff performance at competitive direct operating costs when using high-speed propellers in combination with internally blown flaps. The original tractor configuration is compared to an over-the-wing propeller, which allows for noise shielding. An additional geometry with partially embedded rotor similar to a channel wing is considered to increase the beneficial interaction. This paper shows the aerodynamic integration effects with a focus on climb performance and provides an assessment of the three aforementioned configurations for a simplified wing segment at takeoff conditions. Steady Reynolds-averaged Navier-Stokes simulations have been conducted using an actuator disk model and were evaluated based on the overall design. Interacting with the blown flap, the conventional tractor propeller induces large lift and drag increments due to the vectored sliptream. Although this effect is much smaller for an overthe-wing configuration, by halving the lift augmentation, the lift-to-drag ratio and the propulsive efficiency are considerably improved. Besides a moderate lift gain, the main advantage of a channel wing design is the location of the thrust vector close to the center of gravity resulting in a smaller nosedown pitching moment due to thrust. A disadvantage of over-the-wing propellers is the inhomogeneous inflow at higher velocity, which leads to oscillating blade loads and reduced efficiency.lift coefficient of aircraft C M;y = M y ∕q ∞ · S ref · MAC, pitching moment coefficient of aircraft C P;s = shaft power coefficient C T = 2 · T∕q ∞ · S ref , thrust coefficient of aircraft c = chord length of rectangular wing segment c d = section drag coefficient c l = section lift coefficient c m = section pitching moment coefficient c p = p − p ∞ ∕q ∞ , pressure coefficient D P = propeller diameter p = static pressure q ∞ = dynamic pressure of freestream S ref = wing area of reference aircraft s = semispan of rectangular wing segment T = thrust of one engine T inst = T − ΔD, installed thrust t∕t max = relative blade element thrust V ∞ = freestream velocity α = angle of attack α e = effective angle of attack at blade element β 75= propeller blade pitch angle (at 75% radius) η P = propeller efficiency η Pro = propulsive efficiency ρ ∞ = density of freestream Subscripts x,y,z = Cartesian coordinates

Germany's Fifth Aeronautical Research Program (LuFo-V) gives the framework for the thermoelectric energy recuperation for aviation (TERA) project, which focuses on the positioning of thermoelectricity by means of a holistic reflection of technological possibilities and challenges for the adoption of thermoelectric generators (TEG) to aircraft systems. The aim of this paper is to show the project overview and some first estimations of the performance of an integrated TEG between the hot section of an engine and the cooler bypass flow. Therefore, casing integration positions close to different components are considered such as high-pressure turbine (HPT), low-pressure turbine (LPT), nozzle, or one of the interducts, where the temperature gradients are high enough for efficient TEG function. TEG efficiency is then to be optimized by taking into account occurring thermal resistance, heat transfer mechanisms, efficiency factors, as well as installation and operational system constrains like weight and space.

An approach for estimation of the turbulence length scale at the inflow boundary is proposed and presented. This estimation yields reasonable turbulence decay, supporting the transition model in accurately predicting the laminar-turbulent transition location and development. As an additional element of the approach, the sensitivity of the turbulence model to free-stream values is suppressed by limiting the eddy viscosity in non-viscous regions. Therefore the well known realizability constraint after Durbin [1] is modified. The method is implemented in DLR’s turbomachinery flow solver TRACE in the framework of the k–ω turbulence model by Wilcox [2] and the γ–Reθ transition model by Langtry and Menter [3]. The improved model is tested to the T106A turbine testcase and validated at the T161 turbine cascade under low speed conditions and T170 turbine cascade at high speed conditions.

The aerodynamic integration effects of an embedded over-the-wing propeller at take-off conditions are discussed based on steady and unsteady Reynolds-averaged Navier-Stokes flow simulations. In contrast to the rotating blade and hub geometry, the steady computations utilized an actuator disk model with blade element theory enhancement to investigate the mutual influnce between installed propeller and wing with sufficient accuracy. A simplified high-lift geometry of this channel wing concept is compared to a conventional tractor configuration. While the general overthe-wing integration effects, such as lift-to-drag ratio improvement and deteriorated propeller efficiency, are already captured by inexpensive steady simulations, only unsteady computations with full propeller geometry reveal some important flow details. The most striking unsteady effect is the interaction of the blade tip vortex with the boundary layer of the wing which only occurs at the channel wing due to the close coupling. As a consequence the low momentum fluid detaches above the flap leading to a comparatively low lift coefficient. Nomenclature= advance ratio of the propeller = V ∞ n·D P n = rotation frequency of the propeller p = static pressure q ∞ = dynamic pressure of freestream S = wing area of CFD geometry s = semispan of CFD geometry S re f = wing area of reference aircraft t loc = section thrust of propeller blade T = thrust of one engine V ∞ = flight velocity, freestream velocity x, y, z = cartesian coordinates, as subscript for direction Propulsion and Energy Forum α = angle of attack (AoA) β 75 = propeller blade pitch angle (at 75 % radius) φ = propeller rotation angle η P = propeller efficiency µ t /µ = eddy viscosity ratio ρ ∞ = density of freestream

In a number of recent and former publications, compressor tandem blade configurations show potential to outperform single blade configurations in terms of turning, loss and operating range at high aerodynamic loading levels. However, very little insight is given into the mechanisms of flow breakdown when comparing tandem blades to single blades at large off-design incidence angles. Single blade cascades tend to fail as a result of either pressure side flow separation for high negative incidence or suction side flow separation for high positive incidence, the latter being mostly accompanied by significant increase of underturning. Tandem blade cascades are expected to show a different behavior due to the aerodynamic interaction in the blade overlapping region. Two different tandem blade configurations are examined together with their respective reference single blades, one being a recently designed and optimized tandem blade for high subsonic inlet Mach numbers, which has also been investigated in cascade wind tunnel testing. The other one is a more generic tandem blade based on NACA65 family, designed for medium inlet Mach numbers using current state-of-the-art understanding of tandem design. The mechanisms of flow breakdown are examined using quasi two-dimensional RANS simulations which are validated with test data for one of the aforementioned tandem configurations. A detailed analysis of the flow structure at heavy off-design conditions gives insight into the characteristics of tandem flow breakdown. In particular, the ability of the tandem configuration to extend the operating range to larger positive incidence is described. The shortcomings of the tandem cascade at large negative incidence are also commented. These and further conclusions can be used to improve tandem blade performance at moderate off-design conditions.