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Aircraft have evolved into extremely complex systems that require adapted tools to allow efficient design processes. A new formulation based on an exergy balance is under development at ONERA for assessing the aeropropulsive performance of future aircraft configurations. A control volume analysis is performed to relate the exergy supplied by the propulsion system, its partial destruction within the control volume and the aircraft mechanical equilibrium. The formulation does not rely on the expression of thrust and drag and is therefore especially suitable for the performance evaluation of aircraft configurations with boundary layer ingestion (BLI). A first step towards such applications is the investigation of a more academical configuration consisting in the ingestion by a powered nacelle of the complete wake of a simplified fuselage. Investigation is made via 3D RANS computations and it is shown that the benefit is due to lower levels of exergy destruction in the wake/jet of the BLI configuration.

Aircraft have evolved into extremely complex systems that require adapted methodologies and tools for efficient design processes. A theoretical formulation based on exergy management is proposed for assessing the aerothermopropulsive performance of future aircraft configurations. The theoretical formulation has been numerically implemented in a FORTRAN code to postprocess Reynolds-averaged Navier-Stokes flow solutions. First, the exergy formulation is presented, and then the approach is applied to assess the performance of a simplified (two-dimensional) blended wing-body configuration with boundary-layer ingestion. The challenge of applying conventional drag/thrust bookkeeping is discussed, and the pertinence of the formulation is thereby reinforced. It is shown that this architecture wastes very little exergy in its wake/jet by exhibiting an exergy-waste coefficient lower than 3% in steady flight. Finally, heat transfer upstream of the propulsion system is found to yield an approximate 1.5% fuel saving. Overall, the benefit of the single-currency aspect of the exergy analysis is highlighted.rate of heat anergy supplied by conduction _ A tot = rate of total anergy generation _ A w = rate of anergy generation by shock waves _ A ϕ = rate of anergy generation by viscous dissipation _ A ∇T = rate of anergy generation by thermal mixing _ E p = boundary pressure-work rate _ E q = rate of heat energy supplied by conduction _ E u = streamwise kinetic-energy deposition rate _ E v = transverse kinetic-energy deposition rate _ E ϕ = rate of thermal-energy generation by viscous dissipation e = mass-specific internal energy F x = streamwise resultant force acting on the vehicle h i = mass-specific total enthalpy n = unit normal vector q = heat flux by conduction s = mass-specific entropy V = fluid-velocity vector, V ∞ ux, vy, wz W = aircraft weight Γ = weight-specific aircraft energy height δ = quantity relative to freestream, − ∞ ε = mass-specific flow exergy _ E m = rate of mechanical-exergy outflow _ E prop = rate of exergy supplied by the propulsion system _ E q = rate of heat exergy supplied by conduction _ E th = rate of thermal-exergy outflow τ = viscous stress tensor Φ = dissipation rate per unit volume · = time rate of change Subscripts A = aircraft surface adiab = adiabatic surface O = outer boundary P = propulsion-system surface w = wall ∞ = quantity at freestream conditions

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This paper aims at presenting aerodynamic optimizations carried out at Onera in collaboration with Airbus on the AVECA flying wing configuration using the adjoint approach. Several optimizations were conducted in order to define an optimization scenario to maximize the aerodynamic performance of the AVECA configuration in cruise conditions under geometric and aerodynamic constraints at fixed wing planform. This scenario was then applied to several wing planforms in order to define the influence of the re-optimization to compute the sensitivities of the aerodynamic performance to several wing planform parameters. Finally, a cruise optimization was conducted taking into account a low-speed constraint (Take-off rotational criterion) in order to define a viable flying wing configuration at cruise but also in low-speed conditions. Nomenclature= centre of pressure location y = wing span direction  = vector of parameters X = vector of mesh coordinates W = aerodynamic field  t = turbulent eddy-viscosity LS = low-speed HS = high-speed