Scale-Resolving Simulations of Low-Pressure Turbine Cascades with Wall Roughness Using A Spectral-Element Method

Garai, Anirban ; Diosady, Laslo T ; Murman, Scott M ; Madavan, Nateri K

关键词: SURFACE ROUGHNESS;    TURBOMACHINERY;    CERAMIC MATRIX COMPOSITES;    SIMULATION;    AIRFOILS;    BOUNDARY LAYER SEPARATION;    SUCTION;    DEGRADATION;    GALERKIN METHOD;    FLOW DISTRIBUTION;    SPECTRAL METHODS;    COMPUTATIONAL FLUID DYNAMICS;   

RP-ID  :  ARC-E-DAA-TN53398

学科分类：航空航天科学

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

The accurate prediction of wall-roughness effects in turbomachinery is becoming critical as turbine designers address airfoil surface quality and degradation concerns arising from the shift to advanced ceramic matrix composite (CMC) or additively-manufactured airfoils operating in higher temperature environments. In this paper, a recently developed computational capability for accurate and efficient scale-resolving simulations of turbomachinery is extended to analyze the boundary- layer separation and transition characteristics in a rough-wall low-pressure turbine (LPT) cascade. The computational capability is based on an entropy-stable discontinuous-Galerkin spectral-element approach that extends to arbitrarily high orders of spatial and temporal accuracy, and is implemented in an efficient manner for a modern high performance computer architecture. Results from the scale-resolving simulations of both smooth and rough airfoil cascades are presented and compared to previous experiments and numerical simulations. The results show that the suction surface boundary layer undergoes laminar separation, transition, and turbulent reattachment for the smooth airfoil cascade, while in the presence of roughness the separation and transition behavior of the suction surface boundary layer is substantially modified. The differences between the smooth and rough airfoil cascades are then highlighted by a detailed analysis of their respective turbulent flow fields.