Simulation of three-dimensional viscous flow in turbomachinery geometries using a solution-adaptive unstructured mesh methodology

This paper presents a numerical method for the simulation of flow in turbomachinery blade rows using a solution-adaptive mesh methodology. The fully three-dimensional, compressible, Reynolds-averaged Navier-Stokes equations with k-ε turbulence modeling (and low Reynolds number damping terms) are solved on an unstructured mesh formed from tetrahedral finite volumes. At stages in the solution, mesh refinement is carried out based on flagging cell faces with either a fractional variation of a chosen variable (like Mach number) greater than a given threshold or with a mean value of the chosen variable within a given range. Several solutions are presented, including that for the highly three-dimensional flow associated with the corner stall and secondary flow in a transonic compressor cascade, to demonstrate the potential of the new method.

Detached-eddy simulation of transonic flow past a fan-blade section

Detached-eddy simulation of transonic flow past a thin section of a fan blade has been carried out. The inflow Mach number is 1.03, and a bow shock forms upstream of the blade. The shock (corresponding to an adjacent blade) impinges on the suction-side boundary layer which causes separation and rapid transition to turbulence. The boundary layer later re-attaches near the trailing edge. The pressure-side boundary layer transitions near the leading edge and remains attached. Mean surface pressure shows basic agreement with a steady RANS calculation; strong shock motion in the DES is the major cause of discrepancy. Surface pressure spectra are investigated, and low-frequency two-dimensional disturbances associated with the shock motion are dominant. Removing the two-dimensional component from the spectra, the pressure-side three-dimensional spectra reproduce the spectral shape given by a correlation for flat-plate boundary layer wall-pressure spectra developed by Goody. 1 The suction-side disturbances produce similar high- and intermediate-frequency scalings despite substantially different boundary layer development. Near-wake results show that disturbance kinetic energy peaks at the suction-side inflection point of the mean profile, and that the energy is concentrated at low frequencies relative to the near-trailing edge surface pressure. Copyright © 2009 by the authors.