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Introduction

Turbomachinery flows have long been investigated experimentally and analytically, and more recently, computationally in order to better understand their complicated, inherently unsteady operating environments. Generally, the completeness of computational models has been limited by both algorithms and available computer resources. In particular, unsteady viscous turbomachinery computations have generally been considered prohibitively expensive to use in research and design environments. However, workstations have been shown to make two-dimensional unsteady computations a viable and cost-effective alternative to the use of supercomputers for a research/design environment (Ref. [1]. Three-dimensional unsteady computations are now becoming possible on some top-of-the-line workstations. Distribution of the processing across a network of workstations could further improve the cost-effectiveness of these computations. The concepts involved in extending unsteady turbomachinery computations to a loosely parallel computing environment will be discussed in this paper.

Turbomachinery flows are difficult to compute because of their complicated geometries and because of the relative motion between rotor and stator airfoils. In addition, one must accurately capture flow features such as airfoil potential fields, endwall boundary layer growth, hub corner stall, rotor tip leakage effects and the convection of airfoil wakes in order to compute unsteady forces within the compressor. The current approach uses the two- and three-dimensional Euler/Navier-Stokes equations applied zonally throughout a turbomachine in order to compute these flow features while allowing for relative motion between rotor and stator airfoils. The two-dimensional multistage turbomachinery code STAGE-2 evolved from the two-dimensional single-stage code ROTOR-2 developed by Rai [2]. Similarly, the three-dimensional multistage turbomachinery code STAGE-3 evolved from the three-dimensional single-stage code ROTOR-4 developed by Madavan, et al. [3] The STAGE codes have been designed to be flexible in order to compute flows through turbomachinery geometries that have arbitrary numbers of stages or passages. In addition, the codes operate in both supercomputer and workstation environments.

The STAGE codes have been used to compute flowfields in both turbine and compressor configurations. Two-dimensional results are compared with experimental data and other computations for a 2.5 stage compressor configuration and a single stage turbine configuration. Two-dimensional results include time-averaged pressures and pressure amplitudes on the surface of the airfoils as well as wake profiles. Three-dimensional results for a single-stage turbine configuration are also presented and include time-averaged surface pressure and pressure amplitude on the surface of the airfoils. The results compare well with experimental data and other unsteady computations.


next up previous
Next: Algorithm Up: UNSTEADY TWO- AND THREE-DIMENSIONAL Previous: Nomenclature

Karen L. Gundy-Burlet
Wed Apr 9 13:50:35 PDT 1997