AN ASYMPTOTIC ANALYSIS OF MIXING LOSS

The objective of this paper is to establish, in a rigorous mathematica l manner, a link between the dissipation of unsteadiness in a two-dime nsional compressible flow and the resulting mixing loss. A novel asymp totic approach and a control-volume argument are central to the analys is. It represents the first work clearly identifying the separate cont ributions to the mixing loss from simultaneous linear disturbances, i. e., from unsteady entropy, vorticity, and pressure waves. The results of the analysis have important implications for numerical simulations of turbomachinery flows; the mixing loss at the stator/rotor interface in steady simulations and numerical smoothing are discussed in depth. For a transonic turbine, the entropy rise through the stage is compar ed for a steady and an unsteady viscous simulation. The large interfac e mixing loss in the steady simulation is pointed out and its physical significance is discussed. The asymptotic approach is then applied to the first detailed analysis of interface mixing loss. Contributions f rom different wave types and wavelengths are quantified and discussed.