On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Part II — Numerical Study

Abstract

The transonic flutter cascade facility at NASA Glenn Research Center was redesigned based on a combined program of experimental measurements and numerical analyses. The objectives of the redesign were to improve the periodicity of the cascade in steady operation, and to better quantify the inlet and exit flow conditions needed for CFD predictions. Part I of this paper describes the experimental measurements, which included static pressure measurements on the blade and endwalls made using both static taps and pressure sensitive paints, cobra probe measurements of the endwall boundary layers and blade wakes, and shadowgraphs of the wave structure. Part II of this paper describes three CFD codes used to analyze the facility, including a multibody panel code, a quasi-three-dimensional viscous code, and a fully three-dimensional viscous code. The measurements and analyses both showed that the operation of the cascade was heavily dependent on the configuration of the sidewalls. Four configurations of the sidewalls were studied and the results are described. For the final configuration, the quasi-three-dimensional viscous code was used to predict the location of mid-passage streamlines for a perfectly periodic cascade. By arranging the tunnel sidewalls to approximate these streamlines, side-wall interference was minimized and excellent periodicity was obtained.

Numerical Study on Flow Separation of a Transonic Cascade

“…In the following simulations, the cases with the incidence angle of 0 and 10 , and the inlet Mach number of 0.5, 0.8 and 1.18 are computed and compared with the experimental results. As suggested in [3], the flow incidence angle ahead of the blade will not exactly follow the chordal incidence angle. The incidence uncertainty in the experiment is about 1.5 .…”

Intermittent Flow Regimes in a Transonic Fan Airfoil Cascade

“…This effort was undertaken because research of flutter phenomena in a linear cascade requires very good overall flow uniformity and, in particular, a high degree of flow periodicity over many blades. First, a numerical study was carried out to improve the periodicity of the tunnel and to better quantify the inlet and exit conditions needed for accurate Computational Fluid Dynamics (CFD) predictions (Chima et al, 2000;Lepicovsky et al, 2001). Several configurations of the tunnel endwalls were investigated in order to improve the periodicity of the cascade.…”

“…The configurations were designed using CFD analyses of the complete tunnel and analyses of isolated blades (Chima et al, 2000).…”