Test of the Effect of Vortex Generators in the Diffuser Duct of an UCAV Air Inlet (Forebody Model of Eikon)in FOI Transonic Wind Tunnel T1500

In this report a test in FOI transonic wind tunnel T1500 of a model air inlet is described and some results are presented and discussed. The main purpose of the test was to investigate the effect of vortex generators (VG) placed in the diffuser duct. The reason for using VG was an attempt to improve the highly S-shaped diffuser performance. The model used comprised the foremost part of the geometry of project Eikon. This was done in order to increase the model scale (1:4.33) and consequently obtaining a high Reynolds number (more than 50% of full scale Reynolds number). The test included measurements of total pressure distributions at the AIP and measurements of static pressures on surface upstream the inlet and in the inlet throat and along the diffuser duct. The mass flow rate through was controlled by means of a valve and measured by means of a Venturi nozzle. The model was tested at three free stream Mach numbers (0.6, 0.8 and 0.85), at different angles of attack and sideslip, without and with VGs. The majority of the runs were carried out at maximum corrected mass flow rate, but some limited variation in mass flow rate was performed. Only a limited analysis of the obtained results has been carried out for Mach number 0.85 at zero angles of attack and sideslip. At this condition the effect of the vortex generators is that they seem to spread out the low-pressure regions to a wider area over the AIP. The caused the distortion index DC60 to be drastically reduced (50% or more). The pressure recovery is only marginally changed (if at all) by the action of the vortex generators.