Modeling the response from a cascade to an upstream acoustic disturbance

Time-accurate Euler simulations for the Row through a two-dimensional casca de subjected to an upstream acoustic disturbance were used as the basis for a small-disturbance model to predict the reflected response upstream of th e cascade. The small-disturbance model results in a linear system of algebr aic equations fur the properties of the reflected and transmitted disturban ces. The model predicts the reflected and transmitted responses as a functi on of the cascade blade geometry, the disturbance amplitude, and the initia l Row properties. A new characteristic outflow boundary condition based on the small-disturbance response model was formulated and demonstrated indepe ndently in two one-dimensional Euler codes. The new boundary condition was found to provide a significant improvement in accuracy for the reflection r esponse of an acoustic disturbance from a compressor relative to existing o utflow boundary-condition models.