Ice-Induced Unsteady Flowfield Effects on Airfoil Performance

245 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2003.Vortex structures observed in the shear layer were presumed to be the cause of large-scale pressure fluctuations upstream of reattachment at small angles of attack. Pressure spectra near reattachment exhibited wide bandwidth frequency peaks that indicated a non-periodic phenomenon and corresponded to the regular mode often associated with vortex movement in and aft of the shear layer. Strouhal numbers ranged from 0.53 to 0.73. Although vortex shedding was rarely observed, the convection of surface pressure fluctuations occurred at approximately half the freestream velocity, similar to shedding velocities reported by others.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

An interdisciplinary approach to inflight aircraft icing safety

Abstract Aircraft accidents in icing conditions are primarily the results of the degradation in performance and control due to the aerodynamic effects of the ice. However, despite recent advances in the ability to identify these changes, the icing sensors currently in use sense only ice thickness or accretion rate at the sensor location. No aircraft performance degradation information is available to the pilot. In this paper, a smart icing system is proposed based on the ability to sense the effect of ice on the aircraft performance, stability and control. This concept is proposed through the addition of an Ice Management System to the aircraft. This system would add an additional level of safety to supplement the current avoidance and ice protection concepts currently in use. Such a system would sense ice accretion through traditional icing sensors and use modern system identification methods to estimate aircraft performance and control changes. This information would be used to automatically operate ice protection systems, provide aircraft envelope protection and, if icing was severe, adapt the flight controls. All of this must be properly communicated to and coordinated with the flight crew. The design of such a system requires a coordinated interdisciplinary approach. In addition to describing the basic concept, this paper reviews the research needed in three critical areas; aerodynamics and flight mechanics, aircraft controls, and human factors