Asymmetrical Flow Simulation of Icing Effects in S-Duct Inlets at Angle of Attack

Abstract

The effect of flow angularity on an S-duct inlet with icing is computationally investigated. Flow angularity is simulated through angle-of-attack, and sideslip in addition to asymmetrical ice accretion on the inlet lip. A commercial CFD code, STAR-CCM+ is used for the steadystate computations with the shear-stress transport (SST) k! turbulence model. Symmetrical and asymmetrical glaze ice shapes are computationally simulated on the inlet lip. The symmetrical glaze ice uniformly covers the entire cowl lip; whereas the asymmetrical glaze ice is simulated on a 1=4 sector of the inlet lip and is positioned on top, bottom or side of the inlet lip. The results indicate that flow angularity, whether in angle-of-attack or sideslip, aggravates the low performance of inlets with icing. The total pressure recovery suffers an additional 2% loss and the inlet mass flow rate drops by 7% when the inlet is at C20 angle of attack, as compared to zero angle, for flight Mach number of 0.34. The extent of loss in total pressure and a drop in mass flow rate depends on the asymmetrical icing location as well as the inlet angle-of-attack and sideslip. In addition, the ice-induced flow blockage is identified as a critical inlet performance parameter, since the symmetrical (360) glaze ice with its wider flow blockage creates a lower total pressure recovery than the asymmetrical (90) glaze ice at all angles of attack or sideslip.