An Approximate Analysis of the Unsteady Lift on Airfoils in Cascade

Abstract

An approximate analysis is presented for determining the unsteady lift on airfoils in moving cascades, subject to disturbances in the inlet axial flow. The equations of motion are averaged across the pitch, and the mean pressure in each channel and the pressure difference across it are obtained. The lift on a reference blade dividing two blade channels is then estimated. The analysis is limited to flows in which the frequency parameter based on blade pitch is small, and to blading of low lift coefficient. Comparisons are given with earlier analyses, for flow past isolated airfoils (Sears), for quasi-steady flows through cascades (Gearhart, et al.), and for flow through an actuator disk of small blade chord and flow through cascades of flat blades (Whitehead).