This paper summarizes the investigations performed to evaluate the interference of the wind tunnel walls on the intake flow of a UAV configuration within the framework of Garteur Action Group AG46. Experimental data gathered during a wind tunnel test campaign of the Eikon model -a high-transonic UAV prototype featuring a W-lip, S-shaped intake duct -performed by the Swedish Defence Research Agency (FOI) at the T1500 wind tunnel have been compared to CFD calculations simulating the Eikon model within the T1500 wind tunnel. Numerical results have been compared with experimental data in terms of pressure distribution on the model surface and flow field on the engine-intake Aerodynamic Interface Plane. Additionally, numerical calculations simulating the model both within a closed wind tunnel test section and in free-flight conditions have been performed. Interference of closed and ventilated wind tunnel walls has been evaluated by comparing numerical results in free-flight and within the wind tunnel test section with slotted and closed walls. Nomenclature UAV = Unmanned air vehicle CFD = Computational fluid dynamics AIP = Engine-intake aerodynamic interface plane RANS = Reynolds Averaged Navier-Stokes = Free-stream static pressure , = Free-stream total pressure = Free-stream dynamic pressure = Free-stream static temperature , = Free-stream total temperature = Flow velocity component normal to the wind tunnel wall = Free stream velocity P = Static pressure Cp = Pressure coefficient = EMF = Engine mass flow CEMF = Corrected engine mass flow = , / .!" # , /! !$ " % = Mass flow parameter, ratio of upstream capture area to intake highlight area WT = Wind tunnel L = Intake duct length CDI = Circumferential distortion index (Eq. (3)) RDI = Radial distortion index (Eq. (4))
The aerodynamic propeller–wing interactions of a distributed propulsion system in a high-lift scenario were investigated. A [Formula: see text] computational fluid dynamics parameter study with steady-state Reynolds-averaged Navier–Stokes simulations of a wing segment and an actuator disk was conducted to determine the sensitivities and correlations of design parameters at high angles of attack. The parameter study revealed a significant lift augmentation (about [Formula: see text] at [Formula: see text]) but a decrease in propulsive efficiency (about [Formula: see text] at [Formula: see text]). With increasing angle of attack, the lift augmentation effect decreased (down to about [Formula: see text] at [Formula: see text]), whereas the propulsive efficiency decreased further (to about [Formula: see text] at [Formula: see text]). The design parameter presenting the largest sensitivity toward system performance was the vertical propeller position. The distance between the propeller and the wing had a comparatively minor effect, as long as the vertical propeller position was adapted accordingly. Propulsive performance could be significantly improved by tilting the propeller downward toward the inflow (by about [Formula: see text] for [Formula: see text] as compared to a nontilted propeller). A spanwise clustering of propellers (tip-to-tip distance of [Formula: see text]) appears to be beneficial when considering a predetermined amount of distributed propellers.
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