Response of a Two-Dimensional Cascade

Abstract

Time-accurate Euler simulations of the ow through two-dimensional cascades were used to provide data on the response of the ow entering a compressor to an upstream disturbance. These data were then used to evaluate several compressor face boundary condition hypotheses intended for supersonic inlet stability simulations. An accurate out ow boundary condition for time-accurate Euler/Navier± Stokes simulations of inlet ows is needed to determine the stability margin of an inlet that encounters an atmospheric disturbance. The boundary condition must provide an approximation of the response from the compressor when a disturbance from upstream passes through the inlet and into the compressor face. In the cascade analysis, the blade stagger angle, solidity, shape, and loading; axial Mach number; and disturbance strength were each varied through a representative range. It was found that the response of a cascade to an acoustic disturbance is almost nonre ective for blade geometry parameters characteristic of the compressor hub region and almost at a constant velocity condition for blade geometry parameters characteristic of the blade tip region. A convective (temperature) disturbance was also examined and was found to pass through a cascade without generating an upstream disturbance. Screen, constant Mach number, and constant velocity out ow boundary conditions were evaluated as possible compressor face boundary conditions. It is concluded that the constant velocity boundary condition is preferable to either the screen or the constant Mach number boundary conditions for inlet stability simulations.