Hybrid Airfoil Design Method to Simulate Full-Scale Ice Accretion Throughout a Given a Range

Abstract

A design procedure is presented for hybrid airfoils with full-scale leading edges and redesigned aft sections that exhibit full-scale airfoil water droplet-impingement characteristics throughout a given angle of attack or a range. The design procedure is an extension of a previously published method in that it not only allows for subcritical and viscous-è ow analysis in the design but is also capable of off-design droplet-impingement simulation through the use of a è ap system. The limitations of the è ap-system-based design for simulating both on- and off-design full-scale droplet-impingement characteristics and surface- velocity distribution are discussed with the help of specié c design examples. In particular, this paper presents the design of two hybrid airfoils at two different angles of attack, such that they simulate both the full-scale velocity distribution as well as droplet-impingement characteristics at the respective design angles of attack. Both of the hybrid airfoils are half-scale airfoil models with the nose section matching the full-scale coordinates of the Learjet 305 airfoil back to 5% chord on the upper surface and 20% chord on the lower surface. The effect of è ap deè ection and droplet size on droplet-impingement char- acteristics is also presented to highlight the important limitations of the present method both on- and off- design. This paper also discusses important compromises that must be made to achieve full-scale ice accretion simulation throughout a desired a range and suggests alternatives such as applying a multipoint design approach.