back to the index

Standard configurations

2D geomertry file: STCF5_geo.zip (1 KB).

Download data file

Results on the fifth standard configuration (Fig. 3.5.1, Tables 3.5.1-2) are included by the courtesy of Dr. E. Széchényi at the "Office Nationale d'Etudes et de Recherche Aerospatiale" (ONERA) [Széchényi, 1984; Széchényi et at, 1981a,b]. The original experiments treated a large domain of incidence angles, ranging from attached to stalled flow conditions. In the 1986 report on the standard configurations only the small incidence angles (i_6o) cases were included, as at that time no models for prediction of the stalled cases were proposed. In the meantime a few viscous solvers have become available, and some researchers have asked for more information on the partially and fully stalled flow conditions. An updating of the aeroelastic sample cases of the fifth standard configuration is thus of interest. These updated cases are given in Table Working fluid: Air Maximum blade thickness at x=0.67 d = 0.027 c = 0.090 m span = 0.120 m t = 0.95 camber = 0o g = 59.3o i = 2o->12o M1 = 0.5->1.0 a = 0.00524 rad s: Only one blade vibrated f = 75->550 Hz k = 0.14->1.01 Fig. 3.5.1: Fifth standard configuration: Cascade geometry [Bölcs and Fransson, 1986, p. 124]. 3.5.2, and the experimental data are shown (in listings and plots) in appendices A3 and A4 (for previous experimental results, see also section 7.5 and appendix A5 in Bölcs and Fransson [1986]). In evaluating these data it should be kept in mind that the experimental results are obtained with only one blade vibrating. The data presented do thus not correspond to the time-dependent pressure coefficient in the traveling wave mode as for the other standard configurations, but instead to the eigen-influence of the reference blade on itself when all the other blades in the cascade are fixed. Some researchers have pointed out that the original blade coordinates seem to have some "wiggles" in them when blown up for the numerical calculations. Unfortunately, it is presently not possible to give the profile definition with a better resolution. As with the fourth standard configuration, a smoothing of the data is necessary. The question as how the pressure coefficients have been non-dimensionalized has been brought up. It has been pointed out that a better agreement between the data and one prediction model was found if the data would have been scaled with . A verification of the original results presented has shown that the experimental data have all been non- dimensionalized with the measured upstream dynamic pressure , as originally proposed. Again, as for Standard Configurations 1 and 4, an inconsistency exists between the inlet and outlet flow conditions. Some researchers have compensated this by modifying the inlet flow angle and some by an introduction of a stream tube contraction ratio. Others have left the original values given, and show therefore a less good correlation with the steady-state blade surface pressure distribution. How much these differences in the set-up of the theoretical steady-state flow conditions make out for the time-dependent flow is unclear. Please note that cases 21 and 22 below are for the same flow conditions, with the only difference being the steady-state stagnation pressure. This can give some indications about stagnation pressure influence and the experimental accuracy and should be considered while analyzing the results. Sidén [1991a,c] presents results from a Navier-Stokes solver on incidence angles 2o, 4o and 6o on this standard configuration. He shows a large unsteady pressure in the leading edge region where the experiments indicate a larger value than predictions with a linearized potential model. The viscous solver gives however a considerable overshoot compared to the data. Still, these results indicate the importance of considering viscous effects also at fairly low incidence angles on compressor blades with sharp leading edges. Széchényi [1991] points out that the viscous separation bubble can be well trend wise predicted by a recently developed coupled inviscid/boundary layer code at ONERA [Soize, 1992]. Some of these results have been incorporated in the present data base (see appendix A4).