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The influence of flow spillage before air intake on external aerodynamic characteristics of an aircraft with air-breathing jet engine is studied using CFD tools based on NavierStokes and Euler models. Geometry of the considering vehicle corresponds to one of the versions of the experimental flight test vehicle (EFTV) derived from the LAPCAT-MR2 high-speed passenger cruiser. Research has been performed for Mach number range from 5 to 8 and angles-of-attack from -2° to 8°. It has been shown that the impact of flow spillage on vehicle aerodynamics is significant, and it worth taking into account at the stage of choosing aerodynamic configuration and control system.mass flow rate coefficient 1 = vector of flow momentum at an intake entry 2 = vector of flow momentum at a nozzle exit ∞ = initial vector of momentum of a stream-tube passing through an engine I ∞ = absolute value of the vector I ∞ L = length of a vehicle M ∞ = free-stream Mach number M Σ = resultant aerodynamic moment acting on a vehicle n 1 = unit normal vector to the surface S 1 (directed inwards) n 2 = unit normal vector to the surface S 2 (directed outwards) n w = unit normal vector to the surface S w (directed outwards) Re = Reynolds number p = static pressure p ∞ = static pressure in the free stream R A = external aerodynamic force R Σ = resultant aerodynamic force acting on a vehicle S 0 = intake capture area S 1 = control surface at an intake entry S 2 = control surface at a nozzle exit S w = external surface of a vehicle r = vector from CoG of a vehicle to the considering point T = engine thrust u = flow velocity component in the x direction U ∞ = absolute value of a free-stream flow velocity V = vector of flow velocity1 Head of department, Aerodynamics, anatoly.gubanov@tsagi.ru, not a member of the AIAA. 2 Researcher, Aerodynamics, dmitriy.ivanushkin@tsagi.ru, not a member of the AIAA. 3 Head of sector, Aerodynamics, nina.voevodenko@tsagi.ru, not a member of the AIAA. Downloaded by UNIVERSITY OF ILLINOIS on October 1, 2015 | http://arc.aiaa.org | 2 x = longitudinal direction along the reference axis of a vehicle x a = longitudinal direction along the free stream z a = vertical direction (upwards, normally to the free stream)  = angle-of-attack τ w = local vector of skin friction stress

To anticipate the aerodynamic performance of a slender high-speed vehicle throughout a trajectory, the correct determination of transition onset and extent are crucial parameters in the overall evaluation. Though various methods and correlations are worked out on canonical geometries such as flat plates and cones, the present paper will primarily focus on a slender high-speed vehicle concept. Apart from small leading edge radii and 3D flow effects, also practical considerations are included such as gaps and steps indivertibly present due to manufacturing and integration, differential thermal expansion at dissimilar material interfaces, joints etc... A preliminary assessment based on empirical correlations is challenged by a detailed experimental campaign supported by numerical CFD computations. Their applicability range and their limitations are assessed related to the observed flow phenomena.

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